OmaPhoto/AGENTS.md

# OmaPhoto — agent notes

OmaPhoto is the Linux port of Compositor, the macOS app at https://github.com/robbietilton/Compositor. That repository's Swift tree (`Compositor/`, `CompositorTests/`) is the specification; this repository mirrors it. Its checkout at `../Compositor-spec`, pinned to the tag being ported (v1.3.3 since item 12), is where the Swift sources are read; never edit it for OmaPhoto work.

## Trees

- The repository root: the app. C++20, Qt 6 Widgets (floor Qt 6.4), CMake, Qt Test. CPU raster only: QPainter plus the C kernels in `kernels/`, copied unchanged from Compositor's `Compositor/Rendering/*.c` and compiled in place.
- `packaging/`: the desktop entry, MIME type, icons (Compositor's app icon) and the Arch `PKGBUILD`; `flake.nix` at the root for NixOS.
- `scripts/install/`: one install script per distribution family, each fetching the latest release's package.
- `.github/workflows/release.yml`: a `v*` tag builds the DEB, RPM and Arch package and publishes them.
- `TASKS.md`: ordered task list and progress truth. Its entries before 11.4b speak of the port's old home, `linux/` inside Compositor's repository.

Names: the app is OmaPhoto (binary `omaphoto`, app id `io.github.ZacharyZhang_NY.OmaPhoto`, logging `omaphoto.*`, build options `OMAPHOTO_*`). Compositor's project format stays whole (`.comp`, `application/x-compositor-project`), so projects move between the two apps; C++ types keep their Swift twins' names (`CompositorApp`, `CompositorMenus`).

## Mirror rule

Each Swift file has one Linux twin under `src/` in the same folder (`Document`, `Rendering`, `UI`, `IO`) with the same type and function names. Tests in `tests/` twin `CompositorTests/`. A Swift file over 500 lines splits as `Name+Part`. A Swift extension of `EditorSession` declares its members in `Name+Session.h` (`EditorSession+Brush.h` and `EditorSession+Projects.h` for the extensions named after the session): C++ declares members inside the class, so `EditorSession.h`, the twin of `EditorSession.swift` with every stored property, includes each fragment inside its body. A fragment holds declarations alone, its extension's private helpers under `private:`; state stays in `EditorSession.h`, as Swift keeps stored properties in the class. Qt types are used directly: `QImage` for `CGImage`, `QRectF`, `QPointF`, `QTransform`, `QUuid`. No wrapper types. Nothing outside `UI/` includes `UI/` headers, except where the Swift source does.

Platform adaptations, each forced by a missing Qt analog:

- `ImportedImage` exposes pixels through `image()`, size through `size()`, identity through `identity()`. CoreGraphics backs a painted layer's `CGImage` with a lazy data provider; Qt has none. `image()` flattens painted tiles on first use, so commits, display and history never flatten a layer. Never cache its result in a model type.
- Image identity (`===` on `CGImage`) is `ImageIdentity`: the `RasterSnapshot` pointer for painted assets, `QImage::cacheKey()` otherwise.
- Layer pixels are `QImage::Format_RGBA8888_Premultiplied`; masks are `QImage::Format_Grayscale8`. `BrushRaster::context` makes both.
- Contexts are top-left already, so the CoreGraphics y-flips vanish. `BrushRaster::draw` has no `mask` flag: both CoreGraphics paths are a plain copy in Qt. It takes an optional source part instead of `CGImage.cropping(to:)`, which Qt cannot do without a copy.
- `BrushRaster::visibleRect` stands in for `boundingBoxOfClipPath`.
- Images are drawn into explicit target rects. The positional `drawImage(x, y, image)` scales by the source's device pixel ratio; CoreGraphics never does.
- `DownsampleCache` halves with its own Lanczos-3 filter (vImage has no Linux twin), threaded with QtConcurrent. Swift's label-overloaded `image(_:drawnAt:)` and `image(_:level:)` are `imageDrawnAt` and `imageAtLevel`. Its constructor takes a pixel budget so eviction can be tested; the app uses `shared()`.
- `LayerRenderer::draw` takes Swift's labelled arguments as an `Options` struct. QPainter has no mask clip, so a masked layer is composed aside in device pixels; the mask is drawn with the same placement into a zero-filled `Alpha8` surface and multiplied in 1:1 (`DestinationIn`), so nothing outside the mask survives; the result is composited with the layer's opacity and blend mode. Work that can throw finishes before `save()`. `LayerRenderer` needs a painter on a `QImage`.
- CoreGraphics multiplies nested mask clips inside the context; QPainter has no soft clip. `FolderMaskClip::apply` multiplies a folder mask into device-sized `Alpha8` coverage, `FolderMaskClip::draw` hands each layer the product of its folders' coverage (memoized per folder), and draw routines take it as `LayerRenderer::Options::clip`.
- `TiledLayerRenderer` keeps Swift's pieces, interiors, margins and piece cache, but not its clip surgery. CoreGraphics needs a transparency layer, cleared interiors, subtracted clip paths and device snapping so tiles blend exactly once; the twin draws the base, then for each piece clears and redraws the device pixels whose centres lie in its interior, a half-open `QRegion` computed per scanline, so neighbouring pieces share no pixel and leave none out at any rotation, and the region stays hard while the image keeps its antialiased outline (a path clip turns soft once `Antialiasing` is on). Where an interior ends with its image, the region opens one device pixel outward for that outline, measured through the painter's whole device transform, so it holds at any reduction and under unequal painter scales; the interior already spans the halving overhang there. All of it happens inside `LayerRenderer::composite`, which applies opacity, blend mode, mask and folder clip once. QPainter steps texture coordinates in fixed point, so a piece can differ from the whole image by 3/255 on noise (the tests allow 4 upright, 12 rotated as Swift does). A layer edge off the halving grid differs more, on macOS too: a piece keeps the halving spill past that edge, a whole image crops it (10/255 measured at 0.05×).
- Live strokes reuse that design. `LayerRenderer::composite` takes an optional `veil` callback that repaints the mask coverage after the mask is drawn (coverage starts full when the layer has no mask). `drawStroke` draws the unchanged pixels, then its pieces; where a piece reaches past the old bounds it repaints the coverage with a mask piece (white, then the old mask), so paint there is revealed, where Swift draws a second unmasked pass with holes. `drawMaskStroke` draws the layer once and lets mask pieces replace their interiors of the coverage, where Swift redraws the layer clipped to each piece. A commit's larger pieces take over stretches of the old outline that the base drew during the stroke; the base crops its halving spill, so that outline changes by up to 12/255 on commit, on macOS too.
- `LayerRenderer::drawBrushPreview` replaces Swift's even-odd clips with `CompositionMode_Source` copies into the aside surface, hard-edged (`composite` runs with nearest sampling and the layer's interpolation quality); the source stays clipped to the grid and a raster's base to the source bounds, as Swift's clips keep them. Its `BrushPreview` struct carries Swift's labelled arguments. A raster counts as a source by itself, so a caller never flattens a painted asset just to pass a non-nil image. It throws `std::logic_error` on an empty pixel grid, where Swift would divide by zero.
- `LiveMaskRenderer` has no `bounds`. Swift allocates its coverage and group surfaces over the clip's bounding box, one pixel per user unit, and clips with CoreGraphics; the twin's surfaces are the painter's device in device pixels, drawn with the painter's device transform, because clip coverage must be what `Options::clip` takes. `drawOwn` receives that coverage, and an outer clip (folder masks) multiplies in; a clipping stack composites its group one to one through `LayerRenderer::composite`, under the painter's own opacity as in Swift; `draw` saves and restores the painter around `drawOwn`, exceptions included. The canvas keeps this cheap by painting each dirty rect through an image surface (item 4.4). The constructor takes a pixel budget so tests can reach the limit; passing it, or failing to allocate, logs a warning on `omaphoto.rendering` where Swift skips in silence.
- `AdjustmentSurface::draw` allocates what the painter can show in device pixels (Swift: one pixel per user unit), lets the body draw in the painter's own coordinates, and draws the surface back under the painter's own opacity, composition mode and clip, as `CGContext.draw` inherits them. A surface that cannot be allocated, or passes the budget, logs a warning and draws nothing. On Linux it also gives the hand-blended HSL modes a backdrop on devices without readable pixels (widgets, pixmaps).
- `ImageExporter` is a namespace of functions. Swift's actor only serialises calls; the twin keeps no state, and callers run it off the UI thread. Files are `QString` paths. PNG and JPEG go through `QImageWriter` with an sRGB tag and the resolution as dots per metre; the JPEG preview is read back with `QImageReader`, scaled to 1000 pixels at most. `write` replaces the file through `QSaveFile` and throws `std::runtime_error` with the system's message, where Swift rethrows the Cocoa error. Exports log on `omaphoto.io`.
- `ProjectStore` is a namespace too. Swift's synthesized `Codable` is written by hand in `IO/ProjectStore+Manifest.cpp`: the same keys, the same refusals (wrong types, missing required keys, non-canonical UUIDs), unknown keys ignored, `CGPoint` and `CGSize` as two-number arrays, UUIDs upper case (`uuidString`), two-space indentation so the 4 MiB limit bites where Swift's does. Asset files carry the upper-case names macOS writes; Linux file systems tell the cases apart.
- Saving stages a hidden sibling folder, syncs its files and folders to disk, then swaps it in with `renameat2(RENAME_EXCHANGE)`; a first save is a plain `rename`. Where the system knows no exchange (FAT sticks, old kernels) the store logs a warning and replaces in two moves. Either way the parent folder is synced after the swap, the old project is kept until that sync succeeds, and a failed sync puts it back before the error is thrown. If the way back fails too, nothing is deleted: the old project stays where the swap left it (the hidden sibling, or its `.old` neighbour after two moves) and a critical log on `omaphoto.io` names that path. `ProjectReplaceTests` defines `rename`, `renameat2`, `fsync` and `read` in the test executable, where they take libc's place, to order and fail each call. There is no `NSFileCoordinator`. A missing manifest is `ProjectError(invalid)` and a missing asset `missingImage`, where Swift passes on a Cocoa error; a failed write throws `std::runtime_error` with the system's message. `QFile` reports no error when a read fails after partial data, so the manifest's byte count is checked against the file's size. The manifest's `version`, `width` and `height` are `qint64`, Swift's `Int`, read from Qt's exact integer (`QJsonValue::toVariant` as `LongLong`), never through a double: a wild number decodes and is refused by its own rule, with every digit of its value in the version error. One fact of Qt's parser stays, checked against Swift 6.0.3's decoder: a number token outside Int64, or one with a fraction or an exponent, passes through a double inside Qt. So the 1,024 integers below Int64's minimum and `-9.223372036854775808e18` read as the minimum where Swift refuses them, and `9007199254740993.0` loses its last digit where Swift keeps it. Every such value lies outside each valid range; only the kind or the number of the refusal differs. `ProjectTests` pins one. A whole number with a fraction or an exponent (`5.0`, `5e0`) reads exactly, as Swift's slow path reads it; a token that underflows a double (`1e-400`) fails Qt's whole parse as an illegal number, where Swift reads zero. Only a Grain seed (9.5a), every `UInt32` of which is valid, turns that into a project Swift opens and the twin refuses; `aSeedReadsWhatQtsParserReads` pins it.
- Qt refuses image decodes over 128 MB (`QImageReader::allocationLimit`). `ImageImporter::liftAllocationLimit` lifts that limit for the store and the importer: their own pixel budgets are checked from the file headers before any pixel is read.
- `ImageImporter` is a namespace; the Swift actor only serialises calls and caches a `CIContext`. The type comes from the file's bytes, as `CGImageSourceGetType` reads it: `QImageReader::setDecideFormatFromContent` for JPEG, PNG and TIFF (TIFF needs `qt6-image-formats-plugins`), libheif's `heif_get_file_mime_type` for HEIC (`image/heic`: HEVC in HEIF). Other ISO media (AVIF, plain HEIF, video) and every other format Qt recognises are `unsupported`; bytes nothing recognises are `unreadable`. HEIC decodes through libheif, which applies the file's own turn and crop boxes, so its EXIF orientation is never applied again. Its colours come from the ICC profile, else from the `nclx` box, which ImageIO reads for Swift: the box's primaries (libheif hands over their chromaticities) with the curve it names: sRGB, linear, gamma 2.2 or 2.8 through Qt's own transfer functions, and BT.709's curve (shared by BT.601, BT.2020, xvYCC and BT.1361 between zero and one) as a table; unspecified primaries or curve count as sRGB's, like untagged pixels. Qt 6.4's `QColorSpace` constructor that takes points and a table builds an invalid space (probed), so the table is set afterwards. Curves with no conversion here (PQ and HLG, which need tone mapping; SMPTE 240M, SMPTE 428, the logarithmic ones), primaries Qt cannot hold and a box libheif rejects are `unreadable`, each with its reason in the log: no HEIC imports with colours the importer knows to be wrong. `heif_init` loads the decoder plugins (Ubuntu ships HEVC decoding as `libheif-plugin-libde265`); a missing decoder is `unreadable`, with libheif's message in the log. For Qt's formats the importer reads the pixels as stored, converts them to sRGB while the ICC profile is still attached, and only then applies the EXIF or TIFF orientation itself: Qt 6.4's `setAutoTransform` drops the colour space. Untagged pixels count as sRGB, as CoreImage counts them. Qt 6.4 reads no orientation from a PNG's `eXIf` chunk (probed: `supportsOption(ImageTransformation)` is false), so such a PNG imports as stored; JPEG, TIFF and HEIC turn upright. The result is `RGBA8888_Premultiplied`, tagged sRGB. A thumbnail's long side is 96 and its short side rounds up, as Swift's `extent.integral` does. The HEIC fixtures in `tests/fixtures` are committed; `scripts/heic-fixtures.sh` makes them and stops at the first failure, because the dev image carries no HEVC encoder. The tests patch the lossless `p3-nclx.heic` in memory to name other primaries and curves.
- `LayerRenderer::drawCoverage`: Swift clips to the mask and fills white; QPainter has no soft clip. The twin builds white whose alpha is the mask (premultiplied, from the halved mask `draw` would use, since CoreGraphics filters a shrinking mask and QPainter's bilinear filter aliases) and draws it under the painter's own opacity and clip, in the composition mode under which alpha stands for a clip's coverage: the painter's own for every mode that is linear in the source and keeps pixels where the source is clear (source-over, the blend modes, the rest of Porter and Duff's), and its exact stand-in for the seven that are not (Source and Plus become SourceOver, Clear becomes DestinationOut, SourceIn SourceAtop, SourceOut Xor, DestinationIn Destination, DestinationAtop DestinationOver). `DrawCoverageTests` holds all 24 modes against the oracle, a fill of opaque white mixed in by coverage, over opaque, half clear and clear pixels. Those seven take no painter opacity (CoreGraphics scales the source by it, Qt mixes the result by it, and only linear modes make the two agree): below full opacity they are a `logic_error`, as is any raster operation. No caller sets a mode today. Source-over that is white through coverage, 255 a + d(1 - a), on gray and colour devices alike. It takes the placement `draw` takes, `radians()` included, so a wild angle turns both alike. A mask that is not gray is a `logic_error`; a white image that cannot be allocated is `ExportError(render)`.
- QPainter places an unscaled, unturned image on whole device pixels whatever the hints say; CoreGraphics would blur it by the fraction. Layers the app makes sit on whole pixels, Shape lines aside (8.8), and any scale or turn takes QPainter's filtered path, so tests of soft edges draw under a scale.
- `ImageResizer` and `CanvasResizer` are namespaces. `Task.checkCancellation()` in the Swift resizer has no twin: no caller cancels a resize. Each turns a `std::bad_alloc` into `ExportError(render)` at its door (since 10.1 and 10.2), so the workers that run them catch it. A layer's new box is judged by `LayerTransform::isValid` before any number becomes an integer, where Swift converts first: `Int(Double)` traps on a wild value, C++ would be undefined. Records are rebuilt field by field as Swift rebuilds them, so a field Swift leaves out is dropped once that field exists (the image resizer passes on neither shape, effects nor text; the canvas resizer passes on shape and text, not effects). Options hold `qint64`, Swift's `Int`, like the manifest. `CanvasSizeDraft` keeps plain members where Swift has `let`, so the struct stays assignable.
- `EditorSession` is a `QObject`. One signal, `changed()`, stands in for Swift's observation: every method that changes state emits it, a refused request stays silent, and widgets compare what they show with what the session holds, as `CanvasView.synchronizeDisplay` does. `beginEdit` emits as `endEdit` does, because an open transaction closes `canUndo` and `canRedo`. `fit` and `zoom` emit only when the view changed, so a zoom that is no number stays silent. The canvas edits `viewport` in place and then calls `notify()`. A Swift property with a `didSet` is a private member with a getter and a setter (`activeLayerID`, `isProjectBusy`, `showsNewDocument`, `showsImporter`, `isImporting`, `importError`, `renamingLayerID`); `document`, `tool`, `collapsedGroupIDs` and `selectedLayerIDs` are read through getters and change only through session methods; `history` and `viewport` are public members, as Swift's tests use them. `activeLayer()` returns a copy, as Swift's computed property does. `EditorSessionSignalTests` holds the signal's contract: every change is announced, a refusal is silent, and the last signal of a change sees the state the call leaves behind, read inside the slot.
- `EditorSession.swift` runs to 741 lines, so the twin splits: `EditorSession+Model.h/.cpp` hold `ImageLayer`, `CanvasDocument` and `NavigationTool` (their own header also breaks the include cycle with `DocumentHistory`, which a member by value needs complete), `EditorSession.h/.cpp` the core, `EditorSession+Layers.cpp` the layer operations, `EditorSession+Transform.cpp` the transform edits, `EditorSession+Imports.cpp` the import queue and the busy gates; `EditorSession+Projects.cpp` twins the Swift file of that name. A session function that Swift defines in an extension lives in the twin of that Swift file, declared in its `Name+Session.h`: the `LayerGroups` extension (folders, the multi-selection, grouping, placing, `layerRows`) in `LayerGroups.cpp`, `finishDeletingLayer(s)` in `LiveLayerMask.cpp`.
- `groupSelectedLayers` follows Swift's steps (what stays keeps its place, the folder sits at the topmost selected branch, the wrapped layers go last in hierarchy order) with two terms dropped because they are dead in the twin: the `nil` that ends each ancestor chain (the twin's shared parent starts as the root) and the clamp of the insertion index (it counts layers that stay, so it cannot pass their number). `placeLayer` drops Swift's `target != id` for the same reason: the target is sought after the layer is taken out, so a layer is never found above itself. `canPlaceLayer` is tested by itself as well as through `placeLayer`, whose validation would hide its terms; the panel asks it before a drop. `selectLayers` and `extendSelection` fall back on any selected layer, as Swift's `Set.first` does: tests never depend on which. A session's document always passes `LayerHierarchy::validate` (every mutator checks before it commits), so every `parentID` names a folder of the document; `groupSelectedLayers` reads parents through `std::map::at`, which throws if that ever breaks.
- Transform edits: `TransformEdit` holds what exists so far (`layerID`, `draft`, `group`); `persistent`, `corners`, `mask` and `floating` arrive with the items that read them (`TASKS.md`, "Session hooks owed"). A draft changes only through `previewTransform`, which refuses an invalid value, and begins as a valid transform or box, so it is valid by construction. `commitTransform` therefore gives each layer what `pendingTransform` gives it, one definition for preview and commit, inside one transaction, and skips a layer whose own result is invalid (a box squeezed until a member falls under a pixel); Swift's `edit.draft.isValid` and `firstIndex` guards are left out, since nothing can reach them. An edit that moves nothing records nothing, as in Swift: the history drops a transaction that changed nothing. `canTransform` and `groupTransformMembers` drop Swift's `isGroup` terms (a folder never holds pixels, `LayerHierarchy::validate` sees to it, so `asset` says the same), and `beginTransform` drops `transformEdit == nil` (`canTransform` reads it through `canEditLayers`). `groupTransformBox` keeps `max(1, …)`: rounding leaves a one-pixel layer at origin 1.3 a box under one pixel, and a test holds that. `DistortWarp::corners` came forward from 6.2 for the group box.
- Swift's `async` session calls (`importImages`, `waitForProjectAccess`, `waitForFileRequest`) take a completion callback in the twin. A waiter runs at once when the session allows it; otherwise it is kept, and the setter that frees it posts each waiter to the event loop (`Qt::QueuedConnection`), where it looks again when its turn comes, as a Swift continuation re-enters its `while` loop: no waiter runs inside the setter, and the first may take the project before the second looks. `importImages` takes `QList<QUrl>` (a URL that is no local file is `unsupported`, Swift's `isFileURL` guard), decodes one file at a time through `QtConcurrent::run` and a `QFutureWatcher` (the worker catches `ImageImportError` and hands back the asset or the failure text; anything else is a bug and is left to crash), inserts on the UI thread, and wraps each request in one `Import Images` transaction. A request's callback is posted to the event loop too, so the caller goes on as a resumed Swift task does: after the transaction ended and, for the last request, after `isImporting` fell and the failures were published; for an earlier request while the next one decodes. Only a project that stops being busy frees project waiters: saying busy again leaves them in line. `showsBusy` is a single-shot `QTimer` of `busyIndicatorDelay` (250 ms), a `Qt::PreciseTimer` because a coarse one fires up to a twentieth early, and a child of the session so a test can read its remaining time; tests of time assert floors and states, never ceilings; `createDocument` clears its two flags and then resumes waiting file requests once, where Swift's two `didSet`s each try. The session therefore needs an event loop: every test that makes one uses `QTEST_GUILESS_MAIN`.
- Appearance: `allLayerBlendModes` stands for Swift's `LayerBlendMode.allCases`, the order of the blend menu. Swift's `refreshCanvasPreview` callback has no twin: `changed()` reaches the canvas, and `previewBlendMode` emits it only when the preview changes, so hovering over one entry redraws once. `blendPreview` is a small struct where Swift has a tuple. `opacityEditLayerID` is a private member: only the session reads it; an open opacity drag shows outside as an open transaction (`canUndo` is false). Inside a drag `setLayerOpacity` opens a nested transaction where Swift writes into the open one: the history counts depth, so the drag is still one step, and the branch Swift needs is gone.
- Projects in the session: Swift's `projectURL` is `projectPath`, a `QString`, since files are paths here; it gets a setter when `ProjectController` needs one. Swift builds layers and the document through memberwise initialisers in two places (`installProject`, `applyDocumentSize`); the twin has two constructors for that, `ImageLayer(record, asset, mask)` and `CanvasDocument(snapshot)`, so both places agree by construction; shapes and text set them apart: `installProject` loads both after `CanvasDocument(snapshot)`, `applyDocumentSize` does not, as Swift's rebuild leaves them out. `applyImageSize` and `applyDocumentSize` live in `IO/ImageResizer.cpp`, as in Swift; they build the new document and record the step on a copy of the history before either is published (`DocumentHistory::adopt` takes the copy's steps: its past, its future and its revision, all a closed step changes), then fit the view and signal once, so memory that runs out on the way changes nothing (Swift begins, sets, fits and ends, signalling twice; since 10.1). The twin's document is read-only from outside: a test that needs a state no session call can make (a painted mask, a record with every field set) installs a hand-built `ProjectSnapshot`, where Swift's tests write into `session.document`.
- Masks in the session (`LayerMask.cpp`, after the model): `isMaskSelected` has a getter only, since every Swift write of it sits in a session extension. `TransformEdit` gains `mask`. `commitTransform` hands a mask-alone edit to `commitMaskTransform`, which writes the placement inside one transaction and lets the history drop a change that changes nothing, where Swift compares placements first. In `copyMask` and `toggleMaskLink` Swift's `finishOpacityEdit()` after `commitTransform()` is left out: `commitTransform` has already finished the drag. `tests/SessionFixtures.h` holds `rewrite(session, change)`, which installs a changed snapshot where Swift's tests write a mask, a flip or a sampling into `session.document`; it resets the history as any install does, so steps are counted from there. `tests/SessionRecord.h` holds `described()`, the text of everything an observer can read, shared by the signal test files.
- Live masks in the session (`LiveLayerMask.cpp`): `adoptClipping` and `releaseDetachedClipping` are static members, as Swift's `static func`s. `removeLiveMask` and `releaseDetachedClipping` walk the layers once per parent in list order, where Swift builds sibling arrays; the runs they free are the same. `LiveMaskGraph::validate` already refuses a link to oneself, a folder at either end and a missing source, so `canLinkMask` asks only for editable layers, an existing target and a valid graph; Swift's own checks of those cases, both folder checks of `toggleClippingMask` and `canToggleClippingMask` (the layer's own and its lower sibling's: the store validates the graph on load and `canLinkMask` on every link, so no folder is ever clipped and none becomes a base), and the folder case of the run's base in `releaseDetachedClipping` (nothing is ever clipped to a folder) are dead and left out; both toggle functions take the base from one helper, `clippingBase`. `adoptClipping` keeps its folder check: it writes the link without asking the graph, and `LiveMaskEditTests` calls it directly, because `placeLayer`'s release hides the side of the rule that looks below. `deleteWithLiveMaskChoice` shows a `QMessageBox` from the session, because Swift's session shows an `NSAlert` there: three buttons with Swift's texts (accept, reject and destructive roles), and `LiveMaskDeleteTests` drives the real alert from a zero timer under `QTEST_MAIN`. The bake runs through `QtConcurrent::run` and a `QFutureWatcher` with the project busy; layers are deleted first and the project freed last, as Swift's `defer` does; a failure sets `brushError` (a getter and a setter, arriving here because this is its first writer) and logs a warning. `LiveMaskBaker::bake` draws the target in its own pixel grid and each source through the inverse of the target's pixel-to-document map; the target's own mask, opacity and blend mode stay on the layer. A snapshot that repeats a layer id is a `logic_error` once the target and its pixels are found, where Swift's `Dictionary(uniqueKeysWithValues:)` traps. The bake's worker catches `ExportError` alone, as the import's worker catches `ImageImportError`: anything else is a bug and is left to crash. `releaseDetachedClipping` keys its runs by the optional parent itself, because all zeros is a valid folder id. `PixelAdjust::thumbnail` came forward from 9.2 for the baker. Over the renderer's pixel budget a bake draws nothing, on macOS too.
- `ProjectController` is a `QObject`. Its `async` calls take a completion callback, posted to the event loop like the session's; steps inside continue inline. `newCanvas` and `close` take none: no caller awaits them. The store runs through `QtConcurrent::run` with one `QFutureWatcher` a call, a child of the controller, so an answer dies with it; the worker catches `std::runtime_error` (both of the store's error types) and anything else crashes. Panels are `QFileDialog`s and alerts `QMessageBox`es shown with `open()` over `window` (a `QPointer<QWidget>`), so nothing blocks; without a window they stand alone, where Swift runs the alert modally. A project is a folder: the open panel is in `Directory` mode and takes one project (no `QFileDialog` mode takes several folders, as Swift's workspace panel takes several packages); the save panel is a file panel with the `comp` suffix, and a typed name that is an existing project enters that folder, as any save dialog does (probed; GTK's does too), so Save As cannot land on an existing project. An accepted panel always holds a choice, read as `selectedFiles().value(0)`. A chosen name that does not end in `comp` (in any case) gets `.comp` appended, where `NSSavePanel` enforces the project type: `setDefaultSuffix` only fills in a missing suffix. The panel never saw that completed name, so if anything exists there (a link that leads nowhere counts) the save is refused with an alert and nothing is replaced. `open` trims the slashes at the end of its path, supplied or chosen in the panel: a shell completes a folder's name with a slash, and `QFileInfo` finds no name behind one, where Swift's `lastPathComponent` does. It trims only the end: `QDir::cleanPath` would also collapse `link/..`, which names another folder once `link` is a symbolic link. Callbacks that the session keeps (`waitForFileRequest`, `importImages`) hold the controller through a `QPointer`, because the session may outlive it; everything else hangs on the controller itself (connections, watchers, posted calls) and ends with it. The alert's roles carry the keys: Return saves, Escape cancels. Swift's `session.projectURL = …` is `setProjectPath`, which notifies; `markSaved()` needs no signal of its own, because every path from a save goes on to free the project, and that notifies. `samePlace` compares `canonicalFilePath()`s where Swift compares `resolvingSymlinksInPath()`. There are no recent documents (Qt has no API for the desktop's list) and no security scopes. `receive` keeps Swift's queue: requests drain one at a time from the event loop, each after `waitForFileRequest`; a project is known by its suffix in any case, a trailing slash aside. `tests/DialogDesk.h` answers the real dialogs from a timer: it types into a panel's name field (`selectFile` does nothing while that field has focus) and clicks or keys an alert. While a desk lives the working directory is a temporary folder of its own, so a panel never starts in the source tree (a mutant once saved `Untitled.comp` there and skewed the runs after it).
- `ProjectWorkspace` is a `QObject` with one signal, `changed()`, as the session has: it mutates itself, so the rule for `@Observable` classes that only the session writes does not cover it. `tabs`, `selectedID` and `isManaging` are read through getters. A `ProjectTab` holds its session and controller by value, the session first, and lives in a `std::shared_ptr`, as Swift's tabs are references: a flow that awaits a tab's controller or session (a load, a close, a quit, an import, a copy) keeps that tab alive in its callback until the answer has run, as Swift's `await` does, so a tab removed meanwhile still ends its flow. Every callback the workspace hands to a tab's controller or session holds the workspace through a `QPointer`. Swift's `async` calls take completion callbacks posted to the event loop; `close` takes one too, because its tests await it. The open panel takes one project (see the controller) and is titled `Open Project` like the controller's, where Swift's bare `NSOpenPanel` says `Open`: Qt's default for a folder panel is `Find Directory`. Managing ends last in every flow, after the sessions are free again, so that the workspace's last signal sees `canSwitch` as the call leaves it. A title cuts the suffix as Swift's `deletingPathExtension` does (`nameWithoutSuffix`: a name's first or last dot cuts nothing, so `.comp` stays whole), where `completeBaseName` would leave nothing. `samePlace` falls back on the absolute path (`absoluteFilePath`, which also cleans it) when a place no longer resolves, as `resolvingSymlinksInPath` does, because two missing places both canonicalise to the empty string. A loaded tab's default name is never shown (its title comes from the session's path, which the controller trims), so `loadProject` names it from the path as given. `receive` looks again every 30 ms while the workspace cannot switch, as Swift sleeps; `Task.isCancelled` has no twin. `receiveProviders` takes the drag's `QMimeData`: the layer-row type carries a UUID, judged by its text so that all zeros stays a valid id (a payload under another type is no row and goes to `ImageFileDrop` since 10.4, which reads nothing there); files and pictures arrive with 10.4. `copyLayer` bakes every mask that comes from outside the copy in one worker task (Swift awaits them one by one), then places the layers from a friend's seat in the target session, because Swift writes that document in place; `ProjectController::isProject` and `samePlace` are public statics so that both classes read paths alike. The anchor's `?? centre` fallback is dead (the copied layer is always among the copies) and is a checked read instead.
- `CanvasView` twins `EditorCanvas.swift`, split as `EditorCanvas.cpp` (the display) and `EditorCanvas+Navigation.cpp` (events, cursors, focus; keys in `EditorCanvas+Keys.cpp` since 12.2b). It follows Swift's `updateNSView`: `ContentView` calls `consumeFocusRequest` and `synchronizeDisplay` on every `changed()`, and a canvas alone follows nothing, as Swift's alone observes nothing. `paintEvent` clips to the dirty rect (the region's union, as `draw(_:)` receives it) and paints it through `AdjustmentSurface::draw`, so hand-blended modes and clip coverage meet an image-backed device and device-sized coverage costs only the dirty area; the smooth path draws its layers through a second surface, Swift's transparency layer, so blend modes never meet the checkerboard. `DisplayState` holds what Swift's holds (`brushRevision` came with 8.2, adjustments with 9.5, effects with 9.6c, the crop union in `renderBounds` with 10.1); with a live mask every layer counts, hidden ones included, since a hidden source still clips. The surround outside the document is the palette's `Base`, which the built-in dark sets to Swift's 0.105 gray and a light Omarchy theme to its light `darker_background`, so the welcome reads over it. The shadow is fourteen rings of black stacking to 35% at the edge (Qt has no blur); the border is antialiased, half in and half out, as CoreGraphics strokes it. A wheel without pixel deltas is read in lines, `QApplication::wheelScrollLines()` a notch, twelve points a line as Swift's non-precise scroll; `Qt::ZoomNativeGesture` is `magnify`. Geometry reaches the viewport from the event loop (`syncGeometry` is posted, as Swift defers past SwiftUI's layout) and notifies the session; `QWindow::screenChanged` stands in for `viewDidChangeBackingProperties`. A shown canvas takes the keys when a document exists and no sheet, importer or modal dialog holds them; `EditorSession::requestCanvasFocus` counts Swift's `canvasFocusRequest`, `NavigationToolHeader` asks on Return and Escape, and `ContentView` posts one when a document appears (Swift's `onChange`). Cursors: the open and closed hands for Hand and Space, a drawn magnifier for Zoom (Alt shows the minus), the I-beam for Type, the arrow for Idle and Move (the transform cursors arrive with 6.1), the cross for the rest; auto-repeat releases of Space and Alt are no release. Keys: the tool letters, Space, Escape and Return around a transform edit, arrows nudging in Move; the rest arrive with their tools. Swift's local monitors (`viewDidMoveToWindow`) are an application event filter installed while the canvas is shown: Shift-+ and Shift-− step the blend mode from any control of the window but a text field (`QLineEdit`) or the canvas holding open text (Swift's monitor stands aside for any `NSText` first responder, the inline text view included; since 8.9b), and Alt reaches the Zoom cursor from any window, an open menu's included (Swift's modifier monitor is application-wide); a blend key from another window, a dialog included, is that window's own.
- `BrushRaster::visibleRect` and `AdjustmentSurface::draw` work on widget painters as on images: a widget's `QPainter::device()` measures itself in logical pixels where an image's measures device pixels, `combinedTransform()` carries the device pixel ratio, and `deviceTransform()` also the widget's offset in its window's backing store, whose image is the engine's `paintDevice()`. `HighDpiCanvasTests` holds this at ratio 2 through a `main` of its own that sets `QT_SCALE_FACTOR`.
- `EditorSession::drawLiveComposite` lives in `LiveLayerMask.cpp`, as in Swift, and draws the document as the export does, in document pixels, through the displayed transforms, placements and blend modes; `LayerMaskSessionTests` compares it with the export on every render.
- `ContentView` is one project's editor area, a `QWidget` that compares what it shows with what the session holds on every `changed()`; the window around it is `ProjectWorkspaceView` (4.3c), which owns the toolbar that SwiftUI lets `ContentView` declare. `ToolHeaderBar` carries `Q_OBJECT`: Qt 6.11's `findChild` refuses a class without one at compile time. Every tool has a bar of `ToolHeaderStyle::height`, so the canvas never jumps: a tool whose bar has not arrived yet shows an empty `ToolHeaderBar`, the idle and Eyedropper bars are titles alone, Hand and Zoom share one `NavigationToolHeader`, and a bar put in late is shown at once (a layout shows a late child only from the event loop). The welcome is made anew each time the document goes, as Swift's `if document == nil` makes a fresh view, so its fields and its clipboard suggestion start over. A rail button is a `QToolButton` that toggles itself on a click before the session answers, so the click's slot sets every button again from the session, which a refused `selectTool` leaves silent. `NewCanvasSheet` takes Return and Enter from anywhere on the sheet through widget shortcuts, as SwiftUI's `.defaultAction` does: `setDefault` alone reaches only a `QDialog`. Fonts are set in pixels, Swift's points on a display of one: `setPointSize` would grow them by the screen's DPI. Swift's `.secondary` text is the palette's `PlaceholderText`, its orange warning the palette's `BrightText`, which the theme of 4.5 fills; dividers are `Mid`. Labels and hints say Ctrl and Alt for ⌘ and ⌥. The status bar's hint is an eliding label and the one item that gives way when the window is narrow, as SwiftUI truncates it; zoom and size print through the English locale, as Swift's interpolation groups digits (`1,200 × 800 px`). Swift's last branch gives the Eyedropper the Zoom tool's hint; the twin says the same. Hints and icons that follow tool state (marquee and lasso kinds, brush and smear modes, shape kinds) arrive with that state. `NavigationToolHeader` applies on Return and Escape directly and again when focus leaves, where Swift applies only on the loss of focus: a Qt widget in a window that is not active loses no focus. Text that is no number reads as zero through `toDouble`, which the `> 0` test refuses, so no `ok` flag is read; `inf` reads as a number and the viewport refuses it. `NewCanvasSheet::clipboardDimensions` reads a copied picture's size from its header through `QImageReader` (no pixel is decoded), PNG before TIFF as in Swift, sides swapped for a stored quarter turn. The importer is a `QFileDialog` for existing files, and the two alerts are `QMessageBox`es opened over the view; each is taken down again when the session's flag or error is cleared from elsewhere, as a SwiftUI binding would dismiss it.
- `LayersPanel` twins `LayersPanel.swift`: the heading with its count, `LayerAppearanceControls`, the rows or the empty words, and the footer's `QToolButton`s (new layer, folder, `LayerMaskMenu`, the effects menu since 9.6d, the adjustment menu since 9.5d, delete). Its width is `ContentView`'s `layersPanelWidth`, kept in `QSettings` under Swift's `AppStorage` key; a stored width outside `minimumWidth…maximumWidth` is the default, logged. `PanelResizeEdge` lives in `ContentView.cpp` as in Swift: an 8-point grip with the split cursor over a `Mid` hairline, dragged left to widen, whole points, within range. Tests enable `QStandardPaths::setTestModeEnabled`, which sends `QSettings` to `~/.qttest`. The delete button is Swift's `deleteLayerOrMask` (a chosen effect goes first since 9.6a, then a selected mask, then the selection; since 9.6d its words name a chosen effect first).
- `NativeLayerList` twins the `NSTableView` with a `QScrollArea` of `LayerCell`s, one a row, made anew only when the ids change (a selection or rename reconfigures the cells in place, Swift's "no reload" rule; `nativeSelectionDoesNotReloadRowsAndReorderKeepsIdentity` compares the cell pointers) and shown at once, since a layout shows late children from the event loop. Each cell lays its controls out by hand from Swift's constraints (eye, disclosure, thumbnail, mask link, mask thumbnail, name, size, the effect rows since 9.6e; the depth and a clipping mask each step 24 points in) and keeps a `ThumbnailKey` (asset identity, transform, canvas size) so a picture is redrawn only when what it shows changes. `EyeSwipeButton` and `LayerThumbnailButton` are `QToolButton`s that answer the press themselves. The eye begins a swipe and sets the rows under the drag, scrolling the list by the pointer's overshoot past the viewport as `autoscroll(with:)` does; Swift tracks the drag inside `mouseDown` with a `defer`, so the twin watches the left button's release application-wide (a menu opened mid-press takes it; another button's release leaves the swipe) and a row rebuilt mid-swipe takes the button with it, so its destructor ends the swipe from the event loop, never inside the rebuild that deletes it. The thumbnail follows Swift's `mouseDown` order: Alt on a mask chooses the mask on a release without a drag, Shift toggling it as `selectMask` does (the copy's drag arrives with 4.7), Alt elsewhere is the row's, Ctrl waits for 7.1's selection loading, Shift on a mask targets and toggles it, a plain press targets the pixels or the mask, and every press but Ctrl's then goes to the row with its modifiers, so Shift ranges from the active row without targeting first. A double click with a modifier is a second press of the button's own (Swift's `mouseDown` runs twice), and Alt's on the row's strip clips again; a plain one is left to the row, which renames as Swift's `renameClickedLayer` does for a pixel layer (text opens since 8.9a, an adjustment's settings since 9.5d). `QTest::mouseDClick` on a widget sends the double click alone; the window overload sends the press, release, double click and release a real click brings. The row's own press is `clickRow` (it first lets go of a chosen effect since 9.6e; Alt in the bottom 10 points of the whole row clips to the layer below, Ctrl extends, Shift ranges from the active row, a name click on a lone mask-selected layer commits and targets the pixels, a press on a selected row keeps the selection). A rename is typed in the row's `QLineEdit` (Return keeps, Escape cancels, leaving keeps) and the session's `renamingLayerID` is cleared before the rename, because the rename's own signal would reopen the editor; then the list takes focus, as Swift's `window.makeFirstResponder(table)`. A focus lost to the menu bar or a popup (`Qt::MenuBarFocusReason`, `Qt::PopupFocusReason`) is no leaving, for the editor and the opacity field alike: an `NSMenu` never ends editing. The name and size labels are `Qt::PlainText`, so a name is never read as markup. The context menu is the cell's `actions()`, named as Swift's menu items. Hidden rows fade through a `QGraphicsOpacityEffect`. The list's keys mirror the canvas's (tool letters, Escape and Return around a transform edit, arrows nudging under Move, where every edit sits) and Up and Down walk the rows otherwise, Shift ranging from the anchor as the table's (the far end of the selected run around the active row; the range shrinks back towards it), the row brought into view. A palette change redraws every icon from the event loop, once the widgets carry the new palette: the list's `update`, the panel's and the mask button's icons; a folder's icon keeps its ink in its `ThumbnailKey`. The canvas's application event filter already takes Shift-+ and Shift-− from the list; `BlendShortcutTests` holds both and the text-field exception.
- Drags in the list (`NativeLayerList+Drag.cpp`): a row pressed and moved past `startDragDistance` starts a `QDrag` carrying the row's id, or its whole selection's, one id a line under `ProjectWorkspace::layerType` (Swift writes one pasteboard item a row); Alt at the press offers `CopyAction` alone under `CanvasView::duplicateCursor`, as the table's source mask does, and the drop then duplicates. `dropTarget` is Swift's `validateDrop`: a folder's middle half takes the drop in, the rest lands above the nearer row edge or below every row, every row must pass `canPlaceLayer` (a copied folder carries its contents since 12.2a); `acceptDrop` is `acceptDrop`, the place worked out once, the order reversed into a folder, the moved rows kept selected, one `Move Layer(s)` or `Duplicate Layer(s)` step. Swift refuses a drag from another table by its source; the twin's drag carries its list's token under `sourceType` and a drop takes only its own (Qt's synthetic drop events carry no `source()`, and two projects opened from one file share their layers' ids, so neither would do). A press arms the drag with its modifiers, on the row or on a thumbnail (a thumbnail press that targets goes on to arm the row, as Swift's `mouseDown` falls through to the table); every left press first drops whatever an earlier press armed, then arms unless it clipped (Swift returns after clipping) or was Ctrl's or Shift's; only a move with the left button held past `startDragDistance` starts the drag. An Alt press on a mask watches the left button's release application-wide (a popup opened mid-press takes it), as the eye does; a release seen on a `QWindow` is not counted, since the window sees the button's own release before the button does, and another button's release leaves the press, as Swift waits for the left one. A plain drag offers Move and Copy with Move preferred, so a project target can take the Copy Swift proposes (a tab, the canvas and the New button set `CopyAction` on a valid enter, move and drop and ignore the rest); the list itself duplicates only when a copy is offered alone (Alt at the press), whatever Ctrl makes Qt propose, and sets Move or Copy itself. A drag held near the viewport's edge scrolls the list by the overshoot into a 16-point margin and keeps scrolling on a timer until the pointer moves back inside or the drag ends (a leave or a drop stops it, so no tick reads a drag that is gone), as the table autoscrolls (Wayland sends no moves while the pointer holds still); `autoscrolling()` says whether the timer runs, for the tests. An Alt click that clips sets the cursor for the next click at once, as Swift's refresh after toggling. `LayerColumn` paints the indicator: a two-point accent line between rows or the accent-filled folder row. A mask's Alt-drag carries its layer's id under `maskType`, read back through `ProjectWorkspace::layerID` (a payload that is no id names no mask, an all-zero id included), and lands on the row under the pointer through `canCopyMask`. `QDrag::exec` needs the platform's drag loop, which `offscreen` has not: `LayerDragGestureTests` defines both `QDrag::exec` overloads in the test executable, where they take libQt6Gui's place (as `ProjectReplaceTests` does with libc), record what the drag offered and return `IgnoreAction`, so presses, thresholds and actions are tested to the call; `LayerDragTests` holds the drops and `LayerDragFixtures.h` what both share. The eye and thumbnail buttons live in `NativeLayerList+Buttons.cpp`. With Alt held the viewport's cursor follows the pointer (`cursorFor`): the clipping cursor over a row's strip (create or release, drawn as paths like the symbols, refused where `canToggleClippingMask` says no), the duplicate cursor over the rest of a row (a folder's strip included, since a folder clips nothing, 12.2a) and over a mask thumbnail, the arrow otherwise and with Ctrl; Alt or Ctrl pressed anywhere, and hover over any row or control (every cell and its children track the mouse), reach an application event filter installed while the list is shown, as Swift's `flagsChanged` monitor and tracking area; the list keeps the last hover point, so a modifier change is judged where the pointer sits (`QCursor::pos` is no witness offscreen), and a hover's own modifiers are the event's.
- `EditorSession::duplicateActiveLayer` and `duplicateLayer` (`Document/SelectionClipboard.cpp`, the rest of that extension arrives with 7.4) came forward from 5.1 for the Alt-drag: the copy is the layer with a new id and " copy" after its name, inserted above it, one `Duplicate Layer` step; since 12.2a a folder copies with every layer inside it, new ids throughout, parents and clipping links inside the copy pointing inside it and those outside kept, a collapsed folder's copy collapsed, and nothing past 10,000 layers; `duplicateLayer` selects, duplicates and places the copy inside one transaction, refusing a place `canPlaceLayer` refuses (which reads `canEditLayers`, Swift's first term) and answering false when the limit made no copy.
- `LayerMerge.cpp`, `LayerFlip.cpp` and `Filters.cpp` twin the Swift files of those names (`Filters.cpp` holds `PixelFilter::trimmed` alone until 9.x). `trimmed` returns a `Trimmed` struct where Swift returns a tuple, and reads the alpha bounds straight from a premultiplied `RGBA8888` image, drawing any other format into one first, where Swift always draws into a context. `mergePlan` is a private `MergePlan` struct. `mergeLayers` renders through `drawLiveComposite` into a document-sized context and takes the trimmed image's own size through `ImageLayer(asset, origin)`, where Swift also assigns `trimmed.transform`: at 1:1 the two are equal by construction. Its insertion index counts the kept layers before the anchor, so Swift's `?? layers.count` and the clamp are dead and left out; the hierarchy check stays (a folder selected together with its own child would put the result in a removed folder), and Swift's beeps are warnings on `omaphoto.rendering`, as is a context that cannot be allocated (Swift returns in silence). `flipLayers` reads the group box and the active layer through `value()`, since `canTransform` has proved both, and drops Swift's `ids.isEmpty` guard for the same reason; `commitTransform` has already run `finishOpacityEdit`, so Swift's second call in `mergeLayers` and `flipLayers` is left out. `LayerTransform::mirrored` is declared in `LayerTransform.h` and defined in `LayerFlip.cpp`, as Swift's extension. `beginDuplicateTransform` keeps a private `TransformDuplicate`; a selected folder carries its selected contents, which are no targets of their own, and since the layer limit can refuse a copy, Swift's `copies.isEmpty` branch (the step closed, the selection back) and its `copy != id` test are kept (12.2a); a cancel removes each copy with its contents and their collapsed marks. `commitTransform` ends the duplicate after its own transaction (`endDuplicateTransform`, Swift's `defer`) on the layer path only: `selectLayers` has just made a copy active, so no mask is selected and the mask path never carries one. `cancelTransform` removes the copies, restores the selection and ends it. The Layer menu's Duplicate Layer entry calls `duplicateActiveLayer`, what Swift's `layerViaCopy` does without a selection (7.4 brings the selection); Merge shows `mergeTitle` and Flip Layer follows `canTransform`.
- The Move tool on the canvas (6.1): `TransformOverlay` is no widget. Swift's overlay view exists so that a selection never redraws the pixels; a transparent Qt child would repaint the canvas beneath it anyway, so the canvas draws the handles and guides itself, after its pixels, and `synchronizeDisplay` repaints only the union of the old and the new `drawnRect` (a guide spans the canvas) when the geometry or `snapGuides` changed, leaving its return value to the pixel state. `TransformOverlayGeometry` keeps Swift's handles, rotation grip and `hit`; `showsRotation` and the corner constructor arrive with 6.2. `resizeCursor` maps Swift's frame positions onto Qt's four resize shapes (right, bottom right, bottom, top right). `EditorCanvas+Transform.cpp` holds the drags (`beginTransformDrag`, `dragTransform`, `endTransformDrag`, `cancelTransformDrag`, Swift's `resignFirstResponder`), `transformPressLayer` and `transformCursor`; Ctrl stands for Cmd in picking, Ctrl+Shift extends the selection. The drag's cursor is kept in `m_dragCursor` until the release and outranks Space, where Swift disables the window's cursor rects; hover reaches `updateCursor` through mouse tracking and the last hover point, the application filter reads Alt and Ctrl as it read Alt, and a shown canvas reads both from the keyboard. The release synchronizes the display, so a Ctrl+T edit's guides go without a commit. `moveCursor` (the arrow with Swift's four-way badge) and `rotationCursor` (two arrows round a ring, for the SF symbol) are drawn as paths; the distort cursor arrives with 6.2. `SnapGuides` is a struct where Swift has a tuple, a public member like `viewport`, unannounced; `commitTransform` and `cancelTransform` clear it. `transformSnapTargets` and `snappedMove` live in `Document/Crop.cpp`, Swift's file. `TransformEdit.persistent` sits last, so the positional initialisers keep their order; a drag's edit and a duplicate's are not persistent. `transformAutoSelect`, `showsTransformControls` and `locksTransformRatio` are getters and setters that notify. Escape and Return end a drag with its edit and put the hover cursor back. A press that never moves commits an unchanged edit, which the history drops. The pixel tests hide the controls (`CanvasDisplayTests`, `HighDpiCanvasTests`) and preview through a drag's edit, since Swift's overlay never reaches its `draw` tests.
- Distort (6.2): `DistortWarp` keeps Swift's tests of usability and convexity, `homography` (a projective `QTransform` where Swift returns a closure, Qt dividing by the third row as Swift by `w`), `warp`, `warpTrimmed`, `carried` and `warpMask`. Core Image's perspective filter is `QTransform::quadToQuad` on the image's pixel rect and a `drawImage` under it, antialiased and smooth; a folded shape is two triangles under their affine maps, each a hard device-pixel region of the pixels whose centres the triangle holds, built per scanline from each edge's ends ordered by y, the left bound inclusive, so the halves partition the diagonal and meet a fractional shared edge with one x (a path clip turns soft once the image draws antialiased, and `QRegion`'s integer polygons round the vertices), copied through `BrushRaster::draw` without interpolation, as Swift's. In `distortPreview` a mask warp that throws is caught on its own, as Swift's `try?`: a linked mask covering its layer then draws none, a placed one falls back, with a folded shape, to its stored placement clipped over the warp. Its `Warped` and `Trimmed` structs stand for Swift's tuples; `mapPath` arrived with 8.2b and `distortedEffects` arrived with 9.6c. Swift's `DistortTests` agree since 1.2.1 (`7111885`): a bow tie is usable and folds as two triangles, not convex, and a collapsed corner is refused by both tests; the preview takes a folded shape. `TransformEdit.corners` sits last, after `persistent`. The session's `distortPreview` and `maskDistortPreview` are `const` with mutable caches (`DistortPreviewCache` by layer, `MaskDistortPreviewCache`), keyed by `ImageIdentity` where Swift compares `CGImage` identity, because the canvas reads them from a const session; a warp that throws leaves a cached empty result, as Swift's `try?`. `commitDistort` catches `ProjectError` and `ExportError` into `brushError` as Swift catches its errors; `commitTransform` runs it after the mask path, before the plain one, and ends a duplicate after it. `commitMaskTransform` takes the corners path with `Distort Layer Mask`, `displayedMaskPlacement` its corners cases, `nudgeLayer` moves the corners with the draft. The overlay's corners constructor sets `showsRotation` false, `hit` skips the grip then, and the drawing leaves the stem and disc out; `geometry` returns the corners' geometry for a group or the edited layer. The canvas's `DisplayState` carries the edit's corners, so a moved corner repaints; `drawOwn` draws `distortPreview` first and takes `maskDistortPreview` for the mask. A Ctrl-drag on a handle begins the distortion and drags in `distort` mode with the white `distortCursor`; the cursor shows it over a handle under Ctrl or once distorted. The inspector's numbers rest while corners are set, as Swift's `.disabled`.
- `TransformInspector` is the Move tool's `ToolHeaderBar`: Auto Select and Show Controls as `QCheckBox`es, the numbers in a `QScrollArea` without bars (Swift's horizontal `ScrollView`, which takes the row's spare room and keeps its content at its own size: the row's end stretch rests, the content ends in a stretch of its own), the ratio lock a checkable `QToolButton` with the panel's link icon, the sampling a `QComboBox`, Flip H and V and Cancel and Apply as `QPushButton`s. `TransformValueField` applies as typed (Swift's `isFinite` test is left out: `previewTransform` refuses every transform an infinite number makes), shows the session's number while unfocused and puts it back on `FocusOut`, steps with Up and Down (Shift ten) writing the number it applied, keeps its typing while a menu or popup borrows the focus (`MenuBarFocusReason`, `PopupFocusReason`), and on Return or Escape hands the canvas the keys as Swift's `onSubmit` and `onExitCommand`; the pending edit waits there for the canvas's Return or Escape. From any other control of the bar, Return applies and Escape cancels, Swift's default and cancel actions. The lock's icon is redrawn on `PaletteChange`, as the panel's. Swift's `.id(activeLayerID)` remake is `synchronize` clearing any focus of its own when the active layer changes. `resizeBox` is Swift's `resize`, whose name would hide `QWidget::resize`; its `number >= 1` guard and the scale's `number > 0` are left out: a side under a pixel is a box `previewTransform` refuses. The Layer menu's Transform Layer entry calls `beginTransform` (Swift's `transformCommand` does the same without a selection; 7.4 brings the selection) and the View menu's Show Transform Controls is checkable under Ctrl+H, enabled in the Move tool with a document.
- Selections (7.1): `DocumentSelection` holds a `QPainterPath` where Swift holds a `CGPath`, `SelectionClip` a `QImage` coverage; `SelectionClip::apply` has no twin, because QPainter has no soft clip: `PixelAdjust::coverage` draws the clip's coverage through the layer's inverse `pixelToDocument` into a mask surface (smooth, as CoreGraphics filters a mask clip) and `PixelAdjust::blend` mixes two images through it byte for byte, rounded, where Swift runs `CIBlendWithMask`. Qt's `united`, `subtracted` and `intersected` honour each path's own fill rule and return odd-even paths whose fill is the region they name (probed, `QPathClipper`), so an outline made here is `WindingFill` (a lasso crossing itself fills like Swift's `.winding`, a traced mask keeps its holes) and a result keeps the rule Qt gave it; every fill and `contains` reads the path's own rule, and `QTransform::map` keeps it. Expand and Contract stroke the outline with `QPainterPathStroker` (round cap and join, Swift's `copy(strokingWithWidth:)`; Swift's miter limit is idle under a round join and left out), and a contraction past the middle leaves Qt's empty path, `isEmpty`. `DragBox::rect` rounds with `std::round`, Swift's `rounded()`. The session's selection state is private with getters and setters (`lassoKind`, `marqueeKind`, `selectionModeChoice`, `selectionAntialiased`, the two amounts), `lassoDraft` and `heldSelectionMode` getters alone; `selectTool` cancels a lasso, as Swift's does. `pressMarqueeKey` and `pressLassoKey` arrive with the canvas keys of 7.2; `displayedSelection` with the ants. `PixelInvert::run` is a byte loop where Swift calls vImage (alpha − colour keeps premultiplied transparency), reading any other format as premultiplied first; `invertPixels` takes a completion callback, runs the job through `QtConcurrent::run` and a `QFutureWatcher` with the project busy, and writes back only when the layer still holds the pixels it computed from (identities compared, Swift's `===`); the worker catches `ExportError` alone, the UI side `std::runtime_error` (the clip, the expanded 1×1 mask, the thumbnail), each a warning on `omaphoto.app` and `brushError`. `invertPixels` moves `brushRevision` after its step, as Swift's does. `addMask` from a selection draws the outline through the inverse of `pixelToDocument` into the layer's own grid; a blank layer's grid is its rounded size, as Swift's. `deleteLayerOrMask` is the session function the panel's trash, the Layer menu's Delete and (from 8.x) the Delete key share. The loaders in `MaskTracing.cpp` warn on `omaphoto.app` where Swift beeps, and fetch the pixels inside a try: a painted asset flattens on first use, and a flatten that cannot allocate loads nothing, where Swift's `CGImage` already exists. The Select menu and the Image menu's Invert sit between View and Layer, as macOS places `CommandMenu`s; Select All in a text field is the field's, like Undo (`QLineEdit` takes Ctrl+A itself through `ShortcutOverride`, so the entry's own branch matters only when triggered); Swift agrees since 1.2.0 (`90ee29f`, the responder chain first), and the entry never rests, as Swift's: without a canvas or a field it does nothing. The focus takes it first: a text field, open text, then a focused layer list, which selects every row with the top one primary, as `NSTableView`'s `selectAll(_:)` does in Swift's chain (`NativeLayerList::selectAllRows`), and only then the canvas. The panel's Ctrl-click on a thumbnail loads it (Ctrl-Shift adds, Ctrl-Alt subtracts, as Swift's `loadMode`), the row untouched; with Ctrl held over an enabled thumbnail the list shows `CanvasView::loadSelectionCursor`, a pointing hand drawn as paths with Swift's dashed badge, since `QCursor::pixmap` is empty for a shape cursor. `LayerMaskMenu` calls `addMask` and says in its tooltip what the selection becomes.
- The Marquee and the Lasso on the canvas (7.2): Swift's lasso gestures live in `EditorCanvas+Selection.cpp`, the selection cursors in `EditorCanvas+Cursors.cpp`. The canvas tracks Shift as it tracks Alt and Ctrl (the application filter sees the key from any window, as Swift's `flagsChanged` monitor), and a key change reshapes a Marquee draft and the cursor's badge at once. A press with a selection tool is `lassoMouseDown`; a move is `moveSelectionTool` (a hover moves a polygonal draft's rubber band and refreshes the held keys, as Swift's `mouseMoved`); a release is `releaseSelectionTool`; the draft's keys and the outline's nudges are `selectionKey`, ahead of every other key; losing focus is `endSelectionGestures`. A double click closes a polygonal outline from `mouseDoubleClickEvent`, since Qt delivers the second press there (its first press adds the corner, as Swift's first `mouseDown` does), never while Space pans. A held M or L's repeats are swallowed, as Swift ignores them, so a tool chosen meanwhile stays. An outline drag keeps `moveSelectionCursor` under Space, as the transform drag keeps its own. The ants are a 120 ms `QTimer` stepping `TransformOverlay::antsPhase`, repainting `selectionRect` alone (the outline's own rect, not the handles beside it); `drawnRect` spans the handles, the outline and the draft, the last two stroked antialiased with butt caps (`Qt::FlatCap`, as CoreGraphics dashes: Qt's square caps would stretch each dash by the pen's width) as CoreGraphics strokes them (a 1-point line on whole coordinates blurs over two rows at 1×, on macOS too); `synchronizeDisplay` repaints the overlay when the displayed selection or draft changes, refreshes the overlay's cached rect with every full repaint (a pan moves the outline) and refreshes the cursor when a kind or the displayed mode changes. The two timers are named children of the canvas (`antsTimer`, `marqueeAutoscroll`), as the session's busy timer is, so tests read whether they run. Autoscroll is a 16 ms `QTimer` with Swift's speed curve; each step translates the viewport, drags the draft or the outline again under the still pointer, notifies and synchronizes. `moveSelectionCursor`, `selectionCursor` and `wandCursor` are drawn as paths: the crosshair, the icon haloed by eight white offsets and the badge, and the wand with Swift's own strokes (hot spot 7, 7 at the sparkle, the stick down right, the badge at 17, 5), since `QCursor::pixmap` is empty for a shape cursor; the icons are `Rendering/SelectionIcons`, which the rail's `ToolIcons` and the cursors share, so nothing in `Rendering/` includes `UI/`. `SelectionIcon` is that header's enum, not nested in `CanvasView`. Ctrl over the selection shows the move pointer until 7.4 brings the scissors; the wand's click and cursor are 7.3's. `pressMarqueeKey` and `pressLassoKey` choose their tools and nothing more, as Swift's functions do: Swift's tests once expected a second press to switch the kind, which no Swift code does (its `cycleToolMode` on Tab does, 8.x); since 1.2.0 (`b5cb4fa`) they test the code's rule, as the twin does (`…AndKeepsTheShapeLastSet`), and the twin's tooltips name no key. `LassoControls` is the selection tools' `ToolHeaderBar`: Swift's segmented pickers are checkable `QToolButton`s in a `QButtonGroup`, the amounts are `SelectionAmountField`s (a `QLineEdit` taking digits alone, every typed value clamped to 1–500 as Swift's binding clamps it, stepped by arrows within the bounds, Return and Escape handing the canvas the keys, a menu's borrowed focus keeping the typing as `TransformValueField` does), the wand's controls arrive with 7.3. `ContentView::hint` takes a `ToolIconKind` for the ellipse Marquee's and the polygonal Lasso's words, and the rail's buttons repaint with the kind.
- The Magic Wand (7.3): `WandPixels.c` compiles in place beside the other kernels, and `Document/MagicWand.cpp` wraps it as Swift's `MagicWand` does: `select` draws the image into a premultiplied `RGBA8888` context (the kernel's byte order, rows top down), floors the point, clamps the tolerance and hands the mask to `wand_mask`; `outline` frees the kernel's arrays through `unique_ptr` and builds a `WindingFill` path from its loops. `MagicWandError` carries Swift's two messages (`what()`), `tooDetailed` for the kernel's −2 and `memory` for −1. The session's `magicWand` takes a completion callback and runs the job through `QtConcurrent::run` and a `QFutureWatcher` with the project busy, like the invert; the worker catches `MagicWandError` and `ExportError`, and the UI side applies the outline only while the same document is open (its id, as Swift compares), New with no match deselecting, New with a match `setSelection` without the canvas clip (Swift's shortcut), the other modes `applySelection`. `wandSample` draws the composite through `drawLiveComposite` or the active layer's own pixels through `LayerRenderer::draw` at 1:1, a folder or blank layer as clear; a context that cannot be allocated logs and refuses, as Swift's `try?` returns nil. `wandSettings` is a struct with a setter that notifies; `title` and `radius` stand for Swift's computed properties of `WandSampleSize`. The canvas hands a wand press to `magicWand` with the press's mode, and a click inside the selection to `magicWand` in New mode where another tool would deselect. `LassoControls` shows the wand's controls with the wand alone: the tolerance is a `SelectionAmountField` bounded 0–255, the sample size a `QComboBox` of Swift's titles, the source two checkable buttons, Contiguous a `QCheckBox`; `changeWand` rewrites one field of the settings. The mutant that pins `m_thisLayer` checked is equivalent, since the exclusive group's later `m_allLayers` line decides, as with the marquee's kinds.
- The clipboard (7.4): `SelectionClipboard.cpp` twins Swift's extension as far as the raster edits exist. `PixelClipboard` and `CopiedPixels` (Swift's tuple) live in `Document/SelectionClipboard.h`. `renderSelectedPixels` and `renderMergedPixels` draw into the copy region and multiply the selection's coverage in with `DestinationIn` through `BrushRaster::alphaView` (`clipTo`), where Swift clips the context (`SelectionClip::apply` has no twin); a mask copies as opaque gray with `LayerMask::background` for its ground when placed apart and `LayerRenderer::drawCoverage` for its white, each pass multiplied on its own (the white in a second surface), because CoreGraphics clips both and a soft edge then stacks: half coverage under a white mask is alpha 192, not 128. `store` gives the system clipboard the image and a PNG through `QMimeData`, and counts the clipboard's `dataChanged` signals from the first copy as Swift reads the pasteboard's change count: a paste puts our pixels back in place while the count still matches, else takes another app's image through `QMimeData::imageData`, converted to sRGB first when it carries another colour space (CoreGraphics converts as it draws; `QPainter` copies the numbers), then to the working format, tagged sRGB and centred. A cleared clipboard has no `QMimeData` at all, so `canPaste` checks the pointer. A working copy that cannot be allocated is a warning, as Swift's `try?` beeps there, where a failed Layer via Copy sets `brushError` as Swift's `catch` does. The clipboard is touched only by a copy or a paste, so session tests without one run under `QTEST_GUILESS_MAIN` still; `SelectionClipboardTests` runs under `QTEST_MAIN`. `addPixelLayer`'s shape and text arrived with 8.8 and 8.9a. Swift's `cutSelection`, `PixelMove` and the whole `FloatingSelection` extension need `clearSelectedPixels` and the brush raster, so the cut arrived with 8.2 and the rest with 8.2b, where `canEditLayers` and `ProjectWorkspace::canSwitch` gained their `pixelMove` terms. The Edit menu's Copy and Paste check when chosen, as Swift's (a text field keeps its own, as with Select All); Copy Merged follows `canCopyMerged`; the Layer menu's Ctrl+J is `layerViaCopy`, titled by the selection and enabled as Swift's: `canCopyPixels`, or no selection on an editable layer that is no folder. Swift's beeps are warnings on `omaphoto.app`.
- Content-Aware Fill (7.5): `ContentFill.c` compiles in place beside the other kernels; `Document/ContentFill.cpp` includes its header in angle brackets, because the twin's own header shares the name. `ContentFill::run` draws the job's image into a premultiplied context and takes the pixels to make from `PixelAdjust::coverage` (the selection through the inverse mapping, as Swift clips the mask context and fills white), the kernel's 0 is `ContentFillError(noSource)` with Swift's message and its −1 `ExportError(render)`. `Document/Filters.h` holds what Swift's `Filters.swift` holds as far as it exists: `FilterKind` (`rawValue` and `isAutomatic` are free functions; the other kinds came with 9.4a), `FilterJob` (its settings, scale and seed came with 9.4a), `PixelFilter::run` (the kind's filter, then `PixelAdjust::blend` through the selection) and `FilterEdit`, a plain class in a `std::optional` of the session, since only the session writes it; its `id` stands for Swift's object identity, so a preview lands on the edit it was made for. `FilterEdit` grows through `grow` (the blur's growth and the preview copy came with 9.4a). The session's extension is `Filters+Session.cpp`: Swift's file holds 473 lines, its twin's two halves about 500. `canContentAwareFill` without its `isMaskSelected`, `filterEdit` and `isEmpty` terms (`canAdjustColors` holds all three; it sits in `HueSaturation.cpp`, the twin of its Swift file, alone until 9.3, with the terms that exist), `beginFilter` (`cancelCrop` waits for the crop), `updateFilter` (its settings came with 9.4a), `cancelFilter`, `commitFilter` with a completion callback, `finishFilterCommit` (Swift's guards, the mask carried through `LayerMask::clipImage`). Swift's `previewTask` is one `QFutureWatcher`: `renderFilterPreview` marks the edit preparing and starts the worker, or leaves the job pending behind the one running and runs it when that finishes, a run counting as running until its finish has run (`m_filterRendering`, as Levels' queue); a commit that awaits the preview (`isAutomatic`) is kept in `m_filterCommitWaiting` with its edit's id and called again from `finishFilterPreview` (every waiter is, and one whose edit has gone just returns); the wait is on `preparing`, which only the delivery clears; Preview off is 9.4a's; the workers catch `ContentFillError` and `ExportError` alone. `brushRevision` moves where Swift's does (a delivered preview, Preview switched either way, a cancel, a commit's end), so the canvas's `DisplayState` sees each new preview. `displayedTransform` and `displayedMaskPlacement` take the grown transform while the edit previews, and the canvas draws `previewImage` in the layer's place. `canEditLayers` and `ProjectWorkspace::canSwitch` read `filterEdit`. `FilterSheet` (a `filterPanel`'s content since 9.4b): the kind's words, Preview, the error in `BrightText`, "Limited to the selection" while a selection exists (never for an adjustment layer's editor, since 9.5d), Cancel, the spinner with "Working…" or "Applying…", and OK as the default button, disabled while an automatic kind prepares or failed, so Return then does nothing; Escape and the close button cancel, as Swift's `cancelAction` and `onClose`. The Edit menu's Content-Aware Fill… is Shift+Backspace (Swift's `.delete` is that key) and follows `canContentAwareFill`; the canvas takes Shift with Backspace or Delete ahead of the selection keys, as Swift's `keyDown` does.
- The brush on the CPU (8.1): `Rendering/BrushCoverage` twins `MetalBrushCoverage`: the shader's maths in float, pixel for pixel (the centre sample, the hard tip's antialiased silhouette over `max`, the soft tip's optical density under Gauss–Legendre quadrature per segment at the deposition spacing, the 20 cap, the permanent paint apart from the replaceable tail), one band of 32 rows a QtConcurrent task where Metal dispatched one tile a thread group. A `Tile` keeps the permanent density alone: Swift's preview buffer is the gray coverage context itself, written row by row, so nothing is copied back. A tile that cannot be allocated is `ExportError(render)`. The class with its `shared` device is a namespace. `Document/BrushStroke` keeps Swift's continuous path alone: the dab fallback for machines without Metal (`walk`, `dab`, `tip`, `stamp`, `gridTip`, `falloff`, `drawTail`, `removeTail`, `curve`, `tailBackup`, `distanceToNext`, `dirtyTiles`) is dead where the CPU coverage always exists, and `spacingFraction` stays because the integral reads it. `BrushStroke.swift` runs to 899 lines, so the twin splits: `BrushStroke.cpp` (`BrushRaster`, with `fill`, source-over of a colour at coverage × clip × alpha byte by byte on RGBA and gray alike, 1:1 by construction), `BrushStroke+Stroke.cpp` (the grid, samples, the centripetal Catmull–Rom subdivided within 0.2 px, keys, tiles, coverage and `publish`) and `BrushStroke+Commit.cpp` (`transform(for:)`, `paintSnapshot`, `commitInput`, `BrushCommit` as a namespace, since Swift's actor only serialises). The grid is worked out first (`Grid`) so the const members can follow Swift's `let`s; Swift's guards throw `ProjectError(tooLarge)` as one, and the extent is judged as a double before it becomes an `int`, because past `int` the conversion is undefined where Swift's `Int` just holds the number. The stroke's source is the asset itself (`m_source`, an `ImportedImage`), so a painted layer draws from its tiles and never flattens; `commitInput` hands the asset on, and `BrushCommit::render` draws it the same way. A selection clips the context in Swift; `fill` takes the selection's `PixelAdjust::coverage` on the tile's grid as its clip and rounds coverage × clip × alpha once, as CoreGraphics composites a clipped context. A commit whose crop cannot be allocated is `ExportError(render)`, as Swift's `cropping` returning nil; so is a tile's context that cannot be copied on publish (`QImage::detach` leaves a null image where CoreGraphics' `makeImage` returns nil). Tile keys (row × columns + column) are `qint64`, Swift's `Int`: a small layer scaled to a point across a big canvas passes `int`. A tile is rebuilt whole on every publish (`dirtyTiles` only ever narrowed the dab fallback's rebuilds); `base` is the tile's first pixels, kept apart by QImage's copy on write. `BrushSettings` holds the tip and colour; `erasing`, `healing` and `healingMode` arrive with 8.2 and 8.4, `selectionClip` is here since `publish` reads it, `clone`, `isBlur`, `replacesWithClone`, `editName`, `fillGradient`, `fill`, `clearPixels`, `paintCanvas`, `liftSelection`, `moveLifted` and `heal` with their items. `BrushIntersectionTests` runs the one path where Swift loops over `useGPU`; `BrushTests` holds the stroke-level halves of Swift's session tests, driven on a `BrushStroke` made from a layer, with `LayerRenderer::drawBrushPreview` as the live view and `BrushCommit::render` as the commit; the session halves arrive with 8.2. The early return of a segment past the tip's radius is an equivalent mutant: the density there is zero anyway.
- The session's brush (8.2): `EditorSession+Brush.cpp` twins Swift's extension as far as the tools exist: `canPaint` with the terms that exist (the adjustment term since 9.5a), `makeRasterEdit` (the budgets, the selection clip; `pixelLimit` is `qint64`, Swift's `Int`, and may run below zero when other layers use more than the budget), `beginBrush` for the Brush (Spot Healing joins with 8.4, the other brush tools with their items; erase and the mask's black or white as Swift sets them), `continueBrush`, `shiftLineStart`, `cancelBrush`, `finishBrushImmediately` (busy, it waits; otherwise it flushes and commits the snapshot), `finishBrush` (Swift's `async` wrapper is a plain call here), `commitPaintSnapshot` (the tiles land at once with their undo entry; a mask that covered the old grid is regrown through `RasterSnapshot::replacing`), `commitRasterEdit` (a completion callback, the render through `QtConcurrent::run` and a `QFutureWatcher` with the project busy, the worker catching `ExportError` alone, the UI side keeping Swift's guards and the mask's `isEnabled` as it stands at commit), `usesOpacityKeys`, `typeOpacityDigit` (Swift's uptime is `std::chrono::steady_clock` unless the caller passes a time, as the tests do), `changeBrushHardness`, `changeBrushSize`. `brushStroke` is a `std::unique_ptr` read through a pointer, since a stroke's const members forbid copying; `brushSettings`, `brushMode` (`BrushToolMode` in `Document/SmudgeLiquify.h`, whose smear and liquify arrive with 8.6) and `maskPaintWhite` are getters and setters that notify; `lastBrushPoint` and `pendingOpacityDigit` are private structs. `brushRevision` exists after all, Swift's counter, because the canvas's `DisplayState` must change with every step of a stroke, whose patches it does not hold; a step that changes nothing else repaints the stroke's `dirtyDocumentRect` alone, in view points two points out (`strokeDirtyRect`), as Swift's `setNeedsDisplay` does, and any other change repaints the view. While a folder's mask is painted, the clip for the layers inside comes from the edit's tiles (`liveFolderMaskClip`, Swift's `liveMaskEdit`): `drawBrushPreview` draws the old mask and the patches, nearest, into gray coverage the size of the device, hidden outside the mask's grid, and that multiplies into the folder coverage; the old mask, or a painted mask's base, is halved near the size drawn first, as Swift's `displayImage` does, so a fine mask keeps its shade while painted. The session's private structs (`Decoded`, `Wanded`, `RasterMade` and the rest) live in `EditorSession+Jobs.h` as `SessionJobs` and are aliased in the class, so the header stays under 500 lines. The gates (`canInvert` and `canAdjustColors` among them), `selectLayer`, `selectLayers`, `selectTool` and `selectLayerTarget` refuse while a stroke lasts, `canStartProjectOperation` too, and `importImages` finishes a stroke first, as Swift's do; the tips' parking by tool family arrived with 8.5. `SelectionEdits.cpp` gains `canEditPixels`, `fillSelection` (the palette's colours are black and white until 8.10's `ColorPalette`; on a mask the background is the opposite of `maskPaintWhite`, as Swift's `paletteColor`), `clearSelectedPixels`, `deleteKeyPressed` (its effects term since 9.6a) and `applyPixelEdit`; `cutSelection` sits in `SelectionClipboard.cpp`. `BrushStroke` gains `erasing` in its settings (`BrushRaster::fill` takes `DestinationOut` for it, Swift's blend mode on the context; a mask never erases, so that mode on a gray context is a `logic_error`), `paintCanvas` (the base redrawn, the body under the inverse mapping and a hard canvas clip, then `PixelAdjust::blend` through the selection where Swift clips), `fill` and `clearPixels`; `placedMaskPreview` is declared in `BrushStroke.h` and defined in `LayerMask.cpp`, as Swift's extension, and a preview that cannot be made logs on `omaphoto.rendering` where Swift's `try?` is silent. On the canvas a pixel stroke draws its whole grid placed by `paintTransform` through `TiledLayerRenderer::drawStroke`, a mask stroke through `drawMaskStroke` under the layer's transform, and a mask on its own placement draws the layer through `placedMaskPreview`; the mask's clip takes the stroke's owner as Swift's `base` does. Delete and Backspace without Ctrl, Alt or Meta are `deleteKeyPressed` on the canvas and, plain, in the layer list; Shift with them stays the fill's. The Edit menu gains Cut (Ctrl+X, a text field's own), Fill with Foreground Color (Alt+Backspace) and Fill with Background Color (Ctrl+Backspace), which in a text field delete a word or the line as Swift's `deleteWordBackward` and `deleteToBeginningOfLine` (the selection when there is one, else backwards from the caret, so nothing goes at the start) (reachable from the opacity field alone: a rename or an empty document disables them, as `canEditPixels` does), and Clear Selection Pixels. `tests/BrushFixtures.h` shares the fixtures; `BrushSessionTests` and `PixelEditTests` hold the session halves of Swift's `BrushTests`, `RasterSnapshotSessionTests` the five session cases, `BrushCanvasTests` the two `canvasShift` cases and the canvas's Delete key.
- Moving and floating selected pixels (8.2b): `PixelMove` is a class in `Document/SelectionEdits.h`, Swift's `final class`. Its raster is a `std::shared_ptr<BrushStroke>`, because the canvas draws it while the commit runs, so `commitRasterEdit` takes a `std::shared_ptr<const BrushStroke>` (the brush hands its stroke over); its `offset` starts at zero, since a default `QSizeF` is −1 by −1. `beginPixelMove`, `movePixels`, `finishPixelMove` (a completion callback; the move stays set until the commit lands, so pixels and outline never show at the old place), `cancelPixelMove` and `nudgePixels` (Swift's beep is a warning on `omaphoto.app`) live in `SelectionEdits.cpp`; `displayedSelection` follows a pixel move and a floating edit. `BrushStroke::liftSelection` draws the source into the region, from its tiles when painted, and multiplies the selection's coverage in (`PixelAdjust::coverage` under `DestinationIn`) where Swift clips; `moveLifted` rebuilds each tile from its base, cuts the hole through the same coverage under `DestinationOut` (not for a copy) and places the lifted pixels on whole pixels: a landing between pixels (a scaled or turned layer) is resampled first by its fraction, bilinear and rows in parallel (`BrushRaster::shiftedByFraction`, shared with Clone Stamp), because QPainter snaps an unscaled image to whole pixels (probed on 6.4), where Swift draws it with `.high`. `FloatingSelection.cpp` twins Swift's file: `FloatingTransform` rides in `TransformEdit.floating` (last) as a `std::shared_ptr<const FloatingTransform>`, because the edit is copied freely and holds the whole document from before; `canTransformSelection`, `transformCommand`, `beginSelectionTransform` (a completion callback: the outer `Transform Selection` edit opens, `clearSelectedPixels` runs, and its callback inserts the `Floating Selection` layer), `floatingSelectionTransform`, `mergeFloatingTransform`, `cancelFloatingTransform`, and `FloatingMerge::merge`, a namespace with a `Merged` struct for Swift's tuple. The merge writes pixels, transform and mask into the source layer in place, where Swift rebuilds the layer from listed fields: the fields that list leaves out do not exist yet (`TASKS.md`, "Session hooks owed"). `DistortWarp::mapPath` came forward from 6.2's list: it walks the path's elements (Qt stores a quad as a cubic) and keeps the fill rule. `beginPixelMove` and `canTransformSelection` leave out Swift's `pixelMove == nil`, `transformEdit == nil` and `!selection.isEmpty`, which `canPaint` reads already (through `canEditPixels`). `displayedMaskPlacement`'s `floating == nil` term is dead and left out: the floating layer is made without a mask, and the open edit blocks adding one; `beginDistort` edits the edit in place, so `floating` carries over. The session's private structs sit in `SessionJobs`, now a private base struct of `EditorSession` (the aliases went; `MergePlan` and `TransformDuplicate` joined it), so the header stays under 500 lines. On the canvas a Ctrl-press inside the selection with a selection tool lifts and moves its pixels, Ctrl-Alt copies them, under `movePixelsCursor` (the arrow with scissors drawn as paths and haloed, where Swift badges the SF symbol) or the duplicate cursor, kept under Space as every drag keeps its own; `updateCursor` picks the outline and pixel drags' cursors ahead of Space, so `lassoCursor`, its only caller's helper, checks neither (Swift's has other callers); Ctrl-arrows nudge the selected pixels in any tool, Shift ten, never with Alt or Meta (macOS's Option and Control), ahead of the Move tool's arrows; losing focus cancels a pixel drag; `drawOwn` draws the move's raster as a stroke, and a step repaints the whole view, as Swift's (only a brush stroke repaints its rect). The Layer menu's Ctrl+T is `transformCommand`, titled `Transform Selection` while `canTransformSelection` holds and enabled by either gate. `canEditLayers`, `canInvert`, `canAdjustColors` and `ProjectWorkspace::canSwitch` read `pixelMove`.
- The brush on the canvas (8.3): `EditorCanvas+Brush.cpp` holds Swift's gestures. A press begins a stroke, Shift drawing on from `shiftLineStart` through the press point; a drag continues it, and Shift holds an axis that the first three pixels from its anchor settle (the press under Shift, else the last pixel reached), the pixel waiting at the anchor until then. Swift clears the axis when Shift is let go and again when a new anchor is set; the first is dead and left out. The release reaches its own point, then `finishBrushImmediately` commits. A busy project holds the stroke: a drag, the release, Escape and a lost focus leave it. A stroke goes on only under a drag with the left button, as Swift's `mouseDragged` (a hover after a busy release paints nothing), and wheels and pinches neither pan nor zoom while it lasts, as Swift's `scrollWheel` and `magnify` refuse. A right-drag with a brush tool, no stroke and no Space, sizes the tip from the press (two view points a pixel, rounded, 1 to 2000), or with Shift sets hardness over 200 points, each putting the other back; the circle stays at the press. `BrushCursorOverlay` is no widget, like `TransformOverlay`: the canvas draws the circle last, white 2.5 under black 1, and while hardness is dragged a dashed inner ring (four points on, three off, given in pen widths as Qt counts dashes); `update` returns the old and new rings three points out, as Swift's `setNeedsDisplay`. Swift's `hardness > 0` is dead (a zero ellipse strokes nothing) and left out. The circle follows the pointer, hover included but not a pan (Swift's `mouseDragged` pans first), hides under Space, on leaving and on a lost focus, and shows with the brush tools alone. The canvas's `event` takes Tab before the focus chain (Shift-Tab stays the chain's) for `cycleToolMode`, which switches the Marquee's and the Lasso's shapes, the Brush's mode and Spot Healing's type (the other tools' modes arrive with them); B and E choose the Brush and its mode; a digit reaches `typeOpacityDigit` only where `usesOpacityKeys` holds, else it goes on to the parent, as Swift's `super.keyDown`; brackets step size and hardness, and the application filter takes them from any control but a text field unless the canvas has focus, so a focused canvas's `keyPressEvent` re-reads the modifiers as Swift's `keyDown` does. The layer list takes Tab and Shift-Tab (Swift's table cycles on both), B, E and digits alike. `BrushControls` is every brush tool's `ToolHeaderBar`: Paint and Erase in an exclusive group, size (1–2000), hardness and opacity as a slider in thousandths beside a whole-percent field (opacity from 1%), the sliders following the session under `QSignalBlocker` so nothing rounded is written back, the fields stepping with Up and Down from the session's exact value as Swift's `arrowSteps` does (a slider's 33.3% steps to 34.3%; `SelectionAmountField` takes Swift's `value` and `change` closures, and the Lasso and Wand fields round in `change` as theirs do, an equivalent mutant since their values are whole), and the mask's black-or-white picker and note while a mask is selected; the colour swatch arrived with 8.10a. `ContentView+Status.cpp` holds `percent`, `iconKind` and `hint`, the eraser's words and icon among them; `iconKind` checks its tool although every consumer ignores a kind that is not its own (an equivalent mutant). `updateCursor` and the modifier helpers moved to `EditorCanvas+Cursors.cpp`. `ContentView`'s destructor stops listening first: `~QWidget` closes a shown window after the members are gone, and the canvas's focus-out then notifies (`cancelBrush` bumps `brushRevision`, as Swift's does).
- Brush speed (8.3's gate: 4K at a scale of 2, an 800 px soft brush, median frame at most 8 ms): 6.8–7.4 ms measured, from 47. The soft tip's density comes from a table of 8192 steps over d²/r² from h² to the rim, in radii because hardness alone shapes it, linear between steps; inside h the tip is solid, the table's first value, so a near-hard tip keeps every step across its fade (from 0.9995 on, a table over the whole radius missed the falloff by up to 46 levels). Once the table's steps are finer than float can tell apart ((1 − h²) / 8192 under float's epsilon, from about 0.9995), even that table misses by a few levels: there `tipDensity` evaluates the shader's own formula, float for float, for dabs and segments alike, its solid and empty ends returning at once what the formula yields, so only samples in the thin fade pay for `exp` and `log`. `BrushCoverageTests` holds dabs and strokes on both sides of the switch against the shader's own quadrature, replayed in float. The kernel keeps the shader's order of float operations to the letter (`midpoint ± halfLength · node − projection`, never regrouped): 8192 pixels along a near-hard stroke a regrouping moved a pixel three levels, and a reference written from the twin's own code repeated it. Its one read per lookup is checked at the upper step, so a lost bound aborts. Only a segment passing through the solid core can look up inside it, so the lower clamp runs for those alone (`quadrature<true>`): for every segment it cost 0.3 ms a frame. Bands of 32 rows are the tasks. The halving's bands take their rows, sums and source row from the caller's scratch, so a worker allocates nothing and a failed allocation throws where the caller catches it (QtConcurrent wraps a worker's exception in `QUnhandledException`). `publish` copies each tile and makes its selection coverage on the calling thread, so a failure throws there and a worker's malloc arena never meets a starved allocator, then fills side by side. Pieces compose and halve side by side (`sideBySide`), each halving unthreaded: Qt 6.4 deadlocks on a `blockingMap` inside a map task. The Lanczos colour rows sum four channels in a GCC vector (`vector_size(16)`), each lane as the scalar sum, and the vertical pass runs tap by tap over whole rows; `BrushCoverage.cpp` and `DownsampleCache.cpp` build at `-O3`, where GCC vectorises them. The shadow is skipped when the dirty rect lies inside the document, whose opaque fill covers it. Equivalent mutants: that skip, `fill`'s skip of a zero weight, the colour row's right clamp (it only ever reads padding), the table's interpolation (under a third of a level), its lower clamp at step 1 (the first steps of every fade sit at the density's cap), the clamped quadrature for every segment, the formula for every hardness and `tipDensity`'s two early returns (each only costs time). `BrushPerformanceTests` runs under `BRUSH_BENCHMARK=1`.
- Canvas speed (11.1): `CanvasPerformanceTests` (under `CANVAS_BENCHMARK=1`, at a backing scale of two, as the brush benchmark) pans a 1000-point canvas by trackpad deltas through the canvas's own wheel path, at fit and at Actual Pixels (`zoom(1)`, as the menu sets it), and zooms it in 5% steps around its middle, over a 3840 × 2160 document of ten noise layers (photographs and halves, opacities, multiply, screen, overlay and two Hue layers). Measured on the dev container (32 cores): pan at fit 30 ms median (p95 37), pan at Actual Pixels 68 ms (p95 74), zoom 77 ms (p95 86); with every layer normal 16, 15 and 29 ms. The hand-blended HSL modes are the cost: `HslBlend::blend` ran one thread over the layer's device area, 40 ms a Hue layer at fit; its rows now blend side by side (pointers taken first, since `scanLine` detaches), the same bytes, 3× faster (pan at fit 85 → 30 ms), and the mode is checked before the rows start, since a worker's exception comes back wrapped. At Actual Pixels a Hue layer still costs about 25 ms at 2× (the backdrop's copy and conversion, the enlarged surface and its draw back); the rest is QPainter's single-threaded smooth scaling, about 40 megapixels a frame at this size. Painting the canvas in parallel bands would need its caches (pieces, strokes, effects previews) made safe across threads, and is not done. The guards sit at half again these medians (45, 100 and 115 ms), so a regression fails. Compared with `docs/brush-performance.md`: Swift measures strokes only (2.6–2.8 ms median on macOS); the twin's stroke gate is 8.3's (6.8–7.4 ms at 4K, scale two), and Swift has no pan or zoom figures to compare. `Rendering/PoolMap` (Linux-only) wraps every `QtConcurrent::blockingMap`: Qt 6.4's deadlocks when a pool thread waits on a full pool (a worker's blur or blend on one core, or two workers on two), so a pool thread lends its place while it waits (`releaseThread`, then `reserveThread`, Qt's documented remedy); `PoolMapTests` runs the blend, the blur and a map on a pool of one thread.
- Desktop integration (11.2): the app id is `io.github.ZacharyZhang_NY.OmaPhoto` (Compositor's was its bundle identifier, `com.wonderassembly.compositor`), which names the desktop entry, the icon and the MIME package, and which `main` gives Qt as the desktop file name, so a Wayland compositor matches the window to its entry and icon; on X11 Qt 6.4 names the window class after the application (`omaphoto`, `OmaPhoto`), so the entry's `StartupWMClass` is `OmaPhoto`. `packaging/io.github.ZacharyZhang_NY.OmaPhoto.desktop` launches `omaphoto %F` (files named at launch reach `ProjectWorkspace::receive`, as Finder's Open With reaches the delegate) and lists Swift's two document types: its projects (`application/x-compositor-project`) and JPEG, PNG, HEIC and TIFF. `io.github.ZacharyZhang_NY.OmaPhoto.xml` declares the project type for shared-mime-info, a folder (`inode/directory`) named `*.comp`, commented "OmaPhoto Project", where Swift says "Compositor Project"; a file manager may still open such a folder as a folder, since a project is a directory on Linux. `cmake --install` lays down the app, the entry, the MIME package, Compositor's app icon (`packaging/icons`) at six hicolor sizes (16 to 512) and U²-Net's licence under `share/licenses/omaphoto`; `OMAPHOTO_MODEL`, a path, installs the model as `share/omaphoto/u2net.onnx` whatever its own name, the file itself when given a link (`file(REAL_PATH)`), where `SubjectRemoval` looks, and packages pass it (11.3). A direct install (no `DESTDIR`) runs `update-mime-database` on its prefix, required, so the project type registers at once; a staged install leaves that to the package's hooks. `DesktopIntegrationTests` reads both files, stages an install and compares the whole file list (the model included when the build was configured with one, read from its cache), and installs directly with a stand-in `update-mime-database` first on the path and any `DESTDIR` of the caller cleared; the call in `main` is not under test.
- Packages (11.3): one CMake install serves every package. It lays down the app, its entry, MIME package, icons and both licences (the app's MIT `LICENSE` and U²-Net's, under `share/licenses/omaphoto`), and `OMAPHOTO_MODEL` adds the model. `OMAPHOTO_BUNDLE_ORT` (off by default) installs ONNX Runtime beside the app in `lib/omaphoto` (under the library folder) with the app's run path set there, and Microsoft's `LICENSE` and `ThirdPartyNotices.txt` with it (`OMAPHOTO_ORT_NOTICES`, where the images keep them from the release; a configure that cannot find them fails). Every package bundles (11.4d, issue #5): ONNX Runtime stamps each release's symbols with its version (`VERS_1.20.1`), so a package linked against a system's runtime refuses to install, or to start, once that system updates it. The DEB, the RPM and the Arch package carry Microsoft's 1.21.0 build, pinned by checksum, which the dev, Fedora and Arch images install into `/usr/local` too, so the tests run against the runtime that ships; the flake builds from nixpkgs' own, since Nix rebuilds its closure with it. `DesktopIntegrationTests` expects the runtime (in the configured library folder), its version link and its notices in a bundling build, as it expects the model in a build given one, reading what CMake itself evaluated through compile definitions (both checked by hand in a second build). CPack makes the DEB (Ubuntu) and the RPM (Fedora), each on its own system: the DEB's library dependencies come from `dpkg-shlibdeps`, which finds the bundled runtime through the run path, and it names what no library does (`libheif-plugin-libde265` for HEVC, `qt6-image-formats-plugins` for TIFF, `shared-mime-info`, `hicolor-icon-theme`); the RPM asks for `qt6-qtimageformats`, `shared-mime-info` and `hicolor-icon-theme`, its libraries found by rpmbuild but the bundled runtime left out of what it provides and requires (`__provides_exclude_from`, `__requires_exclude` in `CPACK_RPM_SPEC_MORE_DEFINE`), and suggests RPM Fusion's `libheif-freeworld`, since Fedora's own libheif decodes no HEVC. Packages stage their install (`DESTDIR`), so their systems' hooks and triggers refresh the MIME and icon caches. `Dockerfile.dev` gains `dpkg-dev`, `file` and `fakeroot` for the DEB. `packaging/arch/PKGBUILD` builds this checkout for Arch and Omarchy (`makepkg` there), fetching the model and Microsoft's runtime by their checksums; its `prepare()` lays the runtime out as that build's CMake config expects (`lib64`, `include/onnxruntime` beside `lib/cmake`) and the package bundles it. `flake.nix` sits at the repository root; it builds the app alone and installs staged (`DESTDIR=/`) so the store holds no MIME cache. The DEB was built and read back in the dev image; the RPM, the PKGBUILD and the flake are built on their own systems in 11.4.
- Distro checks (11.4): `scripts/distro-check.sh arch|fedora|nixos|resolute` builds `scripts/distro/<name>/Dockerfile` (for `resolute`, `Dockerfile.dev` on Ubuntu 26.04; Fedora is 43 since 11.4d) and runs dev.sh's configure, build and full test run in it, warnings as errors, as uid 1000 (root ignores the read-only folders and unreadable files the tests make), the tree mounted read-only and `HOME` and `TMPDIR` on a tmpfs (a sync on the container's overlay waits on the host's disk); NixOS builds the flake's package (nixpkgs pinned by the committed `flake.lock`) as root, since Nix writes its store, then runs the tests in its `devShells.default` as uid 1000 (`chroot --userspec`, with `HOME` and `TMPDIR` put back, since `nix develop` points `TMPDIR` at a folder root made); the shell sets the plugin path, the model's data path and a fontconfig file of DejaVu with fontconfig's own rules from the store, since NixOS keeps them in `/etc/fonts/conf.d`, which a container lacks. Every image carries DejaVu Sans, Serif and Mono, the faces the tests name (Fedora splits them into three packages). Ubuntu 24.04 is the dev image itself. What newer Qt and GCC asked for: `QImage::flipped` from Qt 6.9 where 6.4 has `mirrored`; `Q_OBJECT` on every class a test finds with `findChild` (Qt 6.11 refuses one without); `DistortWarp` projects points itself (`project` in `Distort.cpp`), since `QTransform::map` clamps w for points past the horizon from Qt 6.10 (6.10.2 and 6.11.2 probed; 6.4 divides), where Swift divides whatever its sign, and `DistortTests` pins it past the horizon (on 6.4 the two agree, so a mutant there is equivalent); a local pragma for GCC 16's false `-Wmismatched-new-delete` in `DownsampleTests`' replaced operators. Tests follow the systems where only a message or a count differs: libheif 1.23's longer messages, Qt 6.9's TIFF plugin logging libtiff's errors as criticals, fonts named rather than counted, the Type icon's letters in the system's own sans (Fedora's is Noto: the icon sheet compares them only under DejaVu Sans), and `QT_FORCE_STDERR_LOGGING` for the launched app, since a journald-built Qt logs to the journal when stderr is no console. The five starvation tests place their failure by Qt 6.4's own allocations and skip on any other Qt (`placesStarvation` in `AddressSpaceLimit.h`); the limit itself holds there. `ProjectExportFailureTests` opens a panel and an alert once in `initTestCase`, before any limit, as the app's window has before any export: a snapshot that fails opens its alert while the limit holds, and on every system that alert was the process's first font lookup and the panel's first open, costs the app never meets there. In the NixOS shell, which reads fontconfig's whole `conf.d` without a cache, the lookup's failed allocation segfaulted inside fontconfig (`FcHashTableFind`, found under gdb); on the dev image a panel test run alone ran out inside the panel's first open. `theJPEGRenderTakesTheSnapshotWithoutACopy` holds the JPEG render's snapshot to a move under a 2 MB limit, as `thePanelOpensWithoutCopyingTheSnapshot` holds the PNG panel's. The flake leaves out `dev.sh`'s `build/`, which nixpkgs' CMake hook would take for its own build folder.
- Spot Healing (8.4): `HealPixels.c` compiles in place beside the other kernels. `SpotHealingMode`, `allSpotHealingModes` and `rawValue` (Swift's names) sit in `BrushStroke.h`, and `BrushSettings` gains `healing` and `healingMode`. While the stroke lasts its tiles show Swift's wash, gray 0.12 at 45% through the coverage, never erasing. `heal` takes the painted bounds from the kernel's `heal_coverage_bounds`, draws the source into a region about three spots wider, and hands the kernel the coverage packed row by row, as Swift's gray context holds it (the twin copies each tile's rows where Swift draws each coverage image); the seed is `QRandomGenerator::global()`, Swift's `UInt32.random`. Each touched tile is then its base with the healed region copied over, blended with the base through `PixelAdjust::blend` under a selection, where Swift clips the context. The kernel's failure is `ProjectError(tooLarge)`; pixels or packed coverage that cannot be allocated are `ExportError(render)`, as Swift's contexts. The session's `beginBrush` takes Spot Healing on pixels alone, never on a mask, as Swift's guard; `finishBrushImmediately` heals before the commit, one `Spot Healing` step; `spotHealingMode` is a getter and a setter that notifies; Tab steps the type. `isBrushTool` is Swift's four tools: the circle, the right-drag tip, the brackets, the digits and `BrushControls` serve each, and a press with Clone Stamp or the Smear begins nothing until 8.5 and 8.6 bring them. `ContentView` keeps one bar across the four, as Swift's single `isBrushTool` branch keeps its view; the bar titles itself by tool (Spot Healing, Clone Stamp, Smear, Eraser, Brush), shows Paint and Erase for the Brush alone and the three types for Spot Healing alone, and names opacity Strength for the Smear; the clone's Aligned and Sample arrive with 8.5, the Smear's modes with 8.6. Equivalent mutant: the healed tile starting from its context rather than its base, since the region holds the whole wash and the copy replaces it.
- Clone Stamp (8.5): `Document/CloneStamp.h` holds `CloneSettings`, `CloneStamp.cpp` Swift's extension: `setCloneSource` (a point that is no number is refused; a new source restarts the alignment), `cloneStrokeOffset`, `cloneSamplePoint` and `cloneSample`, whose context that cannot be allocated logs on `omaphoto.app` where Swift's `try?` is silent. The session keeps `cloneSource`, `cloneSettings` (a setter that notifies), `cloneOffset` and `parkedBrushTips` by `tipFamily` (Clone Stamp 1, the Smear 2, the rest 0; the two parked tips start at Swift's 40, 0, 1). `selectTool` parks size, hardness and opacity when the family changes and reads the tip it restores with `at`: the session starts in family 0 and leaving a family parks it, so Swift's `if let` always finds one. `beginTransform` and Transform Selection set the Move tool directly, as Swift's do, and park nothing. `beginBrush` takes Clone Stamp on pixels alone, asks for a source first (`brushError`: "Alt-click where Clone Stamp should copy from first."), samples the document as the stroke starts and fixes the offset; Tab toggles the sample; the step is `Clone Stamp`. `BrushStroke::Clone` is Swift's tuple. `publish` makes each tile's view of the sample on the calling thread (`clonePixels`): under a scale or turn QPainter draws it bilinear, Swift's medium quality; a whole translation copies it; a fractional one is drawn at the floor and shifted by `BrushRaster::shiftedByFraction`, since QPainter snaps an unscaled image. `fillClone` then composites it source-over through coverage × opacity × selection, each byte rounded once, where Swift clips the context to the coverage. Swift's `!isMask || isBlur` holds since 8.6: a mask takes a clone only from Blur. The bar shows Aligned (a `QCheckBox` written on `clicked`, so the session's own changes write nothing back), This Layer and All Layers, and "Alt-click to set the source" in `PlaceholderText` while there is no source. On the canvas an Alt-press with Clone Stamp sets the source and paints nothing; Swift's cursor refresh there is dead (Alt is held, so the crosshair stays) and left out. With a source the pointer hides unless Alt or Space is held. `updateBrushCursor` gives the overlay the source crosshair in view points and, between strokes and without Alt, `clonePreview` (the source around the stamped point at screen resolution, at most 1024 pixels, kept under Swift's key; Swift's `.medium` there is overridden by `LayerRenderer`'s own quality and left out) with `cloneTip` (one click painted by the brush engine, kept by size and hardness). `BrushCursorOverlay` gains `marker`, `preview`, `previewOpacity` and `tip`, images compared by `cacheKey` as Swift's `!==`; under an antialiased ellipse clip at the brush's opacity it draws the preview and cuts it to the tip inside `AdjustmentSurface::draw`, Swift's transparency layer, so the tip applies at the drawing's resolution however far a capped preview is enlarged, and draws the crosshair white 3 under black 1 with round caps. A modifier change refreshes the brush cursor, as Swift's monitor does. Equivalent mutants: `displayedTransform` in `cloneSample` and `clonePreview` (it differs from the stored transform only in a transform edit, which leaves Clone Stamp for Move, or a filter edit, which refuses strokes; the preview would show it only with a filter sheet open over Clone Stamp).
- The Smear (8.6): `SmudgeLiquify.h/.cpp` hold `BlurToolMode` and `WarpStroke`, Swift's float arithmetic to the letter (the positive guards of `weight` included) on a document-sized copy drawn through the layer's displayed transform; `image()` is that copy itself, where Swift snapshots it after each append, since the twin reads it only between appends. `beginWarp` and `finishWarp` twin the extension: a warp takes pixels alone (`brushError`: "Smudge and Liquify work on a layer's pixels, not its mask."), and the commit paints the copy along the stroke with a hard tip four pixels wider, `replacesWithClone` so clear pixels clear, one step named by the mode. `BlurTool.cpp` holds `blurSample`: sigma a tenth of the brush within 1.5 and 30; the layer blurred with clear past the document's edge; a mask on its edge tone, its placed box black under its coverage, blurred with the edge repeated. Core Image's Gaussian is `PixelAdjust::gaussianBlur`: separable, weights exp(−i²/2σ²) over three sigmas, normalised, in float on the stored premultiplied values (Swift's Core Image context is unmanaged), each byte rounded once, rows in parallel. Where Core Image approximates a large blur, the twin's is exact; it costs 20–110 ms for a 4K document on 32 cores (sigma 1.5 to 30), paid as a Blur stroke begins, since Swift's sample is taken whole. `BrushStroke` gains `isBlur` (a mask takes a clone only from Blur), `replacesWithClone` (a copy by coverage: `fillClone` keeps 1 − coverage of the old pixel) and `editName` (the step's name when set). `clonePixels` resamples every clone, a gray one too, into premultiplied colour, so a sample's edge keeps the share of the pixel the image covers, and `fillClone` composites that alpha into a mask as CoreGraphics draws a gray image's edge: a white mask half a pixel past the canvas stays white. The session keeps `blurMode` and `warpStroke`; `beginBrush` hands Liquify and Smudge to `beginWarp`; `continueBrush`, `cancelBrush` and `finishBrushImmediately` take the warp first; exactly Swift's six places read it: `canEditLayers`, `canUseHistory`, `canStartProjectOperation`, `selectLayer`, `selectTool`, `cycleToolMode` (`selectLayers` and `selectLayerTarget` read the brush stroke alone, as Swift's). Tab steps the Smear's modes. The bar shows the three modes with Swift's help; the status line says "Drag to soften", "Drag to smudge" or "Drag to push pixels" (`hint` takes the Smear's mode). On the canvas the warp's copy stands in for its layer across the canvas, through the layer's mask at 2048, its opacity and blend mode, and a step repaints the view (no dirty rect, as Swift's); drags, releases, Escape, wheels, pinches and the tip drag treat a warp as a stroke. Equivalent mutants: `displayedTransform` in `beginWarp` and `blurSample` (painting refuses transform and filter edits), the radius rounded to nearest (pixels past its floor lie outside the brush), `u >= h` for `u > h` (weight 1 either way), a warp without dabs going on to commit (it appends nothing), copy mode weighing by coverage times opacity (a warp commits at full opacity), `fillClone`'s format guard (a clone is always sampled in colour), and the Gaussian's branch-free interior moved by a pixel (it reads one tap weighing under 1% of the centre).
- The Gradient (8.7): `Document/Gradient.cpp` twins Swift's extension. `GradientEdit` is a struct in a `std::optional`, where Swift's is a class; its raster is a `std::shared_ptr<BrushStroke>`, as a pixel move's, because the canvas draws it while the commit renders, and the raster's pointer stands for Swift's `gradientEdit === edit` (a new line on the same target keeps the raster, as Swift keeps the edit). `commitGradient` takes a completion callback, posted on every path; `resolveGradient` posts the commit, Swift's `Task`, so a switch of tool, layer or target applies it once the caller returns; `invertPixels` and `beginFilter` commit it first and call themselves again from its callback, as Swift awaits it. `fillGradient` fills the canvas through `paintCanvas` with a `QLinearGradient`, or a `QRadialGradient` centred on the start with the line as its radius; Qt's pad spread is CoreGraphics' `drawsBeforeStartLocation` and `drawsAfterEndLocation`, and two stops interpolate alike in both. `gradientColors` makes a mask's colours gray from the palette's red, where Swift makes `DeviceGray` colours. `undo` first discards a pending gradient and `canUndo` counts one, as Swift's. The palette's model came forward from 8.10 into `ColorPalette.cpp` (`PaletteColor`, `foregroundColor` with `setForegroundColor` through `setBrushSettings`, `backgroundColor`, `canEditPalette`, `paletteColor`, `setPaletteColor`, `swapPaletteColors`, `resetPaletteColors`), and `fillSelection` reads it; the Type bar's share of `setPaletteColor` came with 8.9a, the picker and the swatches came with 8.10a. On the canvas (`EditorCanvas+Gradient.cpp`) a press within ten points of the end, then the start, grabs it, else begins a line; Shift turns the dragged end to a multiple of 45° around the other; Escape cancels and Return or Enter applies, after the selection's keys; losing focus drops the drag. `TransformOverlay` draws the line in place of the handles while one is pending, as Swift's: a radial's dashed rim at the line's length, the line black 3 under white 1, each end a white disc with a black rim, a gray ring and its colour. A pending gradient on a folder's mask clips the folder's layers at once through `liveFolderMaskClip`, as a brush stroke does. `GradientControls` is the tool's `ToolHeaderBar`: the shapes as checkable `QToolButton`s in a `QButtonGroup`, `GradientSwatch` (white, gray checks of four points, the colours, clipped to a rounded rect, the rim unclipped as Swift's `strokeBorder` overlay), the style `QComboBox`, Reverse, the slider in thousandths from 1% and the percent field (a `SelectionAmountField`, whose own clamp stands for the binding's), the Mask note in `PlaceholderText`, and Cancel and Apply while pending. Equivalent mutants: the gray branch of `gradientColors` and of `fillSelection` (a mask's palette is black or white), and the swatch's rim clipped too (3/255 at its corner pixels, measured). A press that marks a drag without an edit was equivalent until 8.10b's Alt eyedropper read the drag; a test holds it now.
- The Shape tool (8.8): `Document/ShapeTool.h/.cpp` twin Swift's file, `ShapeTool+Session.h` its session half. `ShapeKind`'s raw values, `shapeKind(text)` for the manifest and `path` stand for the enum and its `path(in:cornerRadius:)`; `LayerShapeStyle`, `LayerShape` and `ShapeDraft` keep Swift's fields, `ShapePreview` is Swift's tuple. A `LayerShape` holds its image's `ImageIdentity`, Swift's `===`, since `ImportedImage::image()` is never cached in a model type; `ImageLayer.shape` joins equality, and `liveShape()` compares identities, so any other change to the pixels leaves a shape that is no longer live. `addPixelLayer` takes the style and ties it to the asset it makes, where Swift passes a `LayerShape` made from the same image. `shapeKind`, `shapeCornerRadius` and `shapeLineWidth` are getters and setters that notify, `shapeDraft` a getter. `finishShape` truncates each side before multiplying, as Swift's `Int()`, in doubles; a Line click leaves a dot as wide as the line, since the box grows by the thickness, as in Swift. `strokedLine` gives a line's round-capped outline, filled on the layer and on the draft, because QPainter draws a pen a pixel wide through its thin-line path, whose diagonals cover less than CoreGraphics' stroke; a zero-length line is a disc, since CoreGraphics caps it as a dot (PDF's rule for round caps) where Qt draws nothing. `redrawShape` pins any mask where it shows (Swift's `placement == nil` test changes nothing: a placed mask's `maskTransform` is its placement) and logs on `omaphoto.app` where Swift's `try?` is silent; `shapeTransformPreview` is `const` with a mutable cache, reads the pixel size from the asset a live shape shares, and logs on `omaphoto.rendering`. Left out as dead or redundant: `path`'s `max(0, …)` (its `radius > 0` test sends a negative radius to the plain rectangle), `shapeLineEnds`'s kind test and the draft drawing's `guard let ends` (only a line's drag sets an end, and its box with it), `finishShape`'s zero-width fallback in `unit` (the box is a pixel wide by then), `redrawShape`'s `max(1, …)` (a valid transform is a pixel wide), and the canvas drag's `lastDragPoint == nil` (a pan never begins a draft). Hooks: `selectTool` cancels a draft, Tab steps the kind, `commitTransform` redraws each moved shape, the record carries a live shape's style (`hierarchyRecord`), `installProject` loads shapes and `applyDocumentSize` does not, as Swift's rebuild leaves them out after a crop or a resize; where Swift rebuilds a layer (a brush or raster commit, Invert, a filter, a floating merge) the twin drops the shape in place; the canvas resizer passes it on, the image resizer not; a duplicate or a copied layer keeps it. The manifest's `shape` key is Swift's `Codable`: the kind's raw value, the numbers, `lineWidth`, `start` and `end` only when set, points as two numbers; a wrong type or a missing key refuses the project. On the canvas (`EditorCanvas+Shape.cpp`) a press begins, a move drags (Shift squares or snaps a line, Alt grows from the centre), the release finishes, Escape cancels after the selection's keys, Shift-U steps the kind with the Shape tool and chooses it otherwise, losing focus cancels. The draft draws above the active layer, inside the live mask renderer's `drawOwn`, composed aside through `LayerRenderer::composite` so folder masks clip it; a line at its width times the zoom, a point at least, with round caps. Swift's draw reads the draft under AppKit's observation tracking; the twin's `synchronizeDisplay` compares `ShapeShown` (draft, colour, width, the layer it sits above) and redraws the view as that observation does, where the brush repaints its stroke's rect alone; `DisplayState` counts a blank layer while a draft sits on it, so moving or hiding the target redraws too. A rounded rectangle resized with the Move tool draws `shapeTransformPreview` in place of its pixels. `ShapeControls` is the tool's `ToolHeaderBar`: the kinds as checkable `QToolButton`s in a `QButtonGroup` (a choice drops the draft first), Width for lines (a slider of 1–100 showing at most 100, a `SelectionAmountField` of 1–5000, "px") and Radius for rectangles (0–200 and 0–5000, with Swift's help); the sliders show the session's number without writing it back; the Fill swatch came with 8.10a. The status hint follows the kind. Known difference: a Line layer's box follows the dragged point, so it can sit between pixels, and at 1:1 and in exports QPainter draws it on whole pixels, where CoreGraphics interpolates. Equivalent mutants: Qt's `addRoundedRect` adds a plain rectangle at radius 0, so `radius > 0` and `>= 0` agree; an undragged draft's box is its anchor, so `finishShape`'s `value_or` may take either; the draft drawing's empty-box test for a rectangle or ellipse only spares an empty surface, since a path of no area paints nothing.
- The Type tool (8.9a): `Document/TypeTool.h/.cpp` twin Swift's file, `TypeTool+Session.h` its session half. `TextAlignment`'s raw values and `textAlignment(text)` serve the manifest; `LayerTextStyle`, `LayerText` and `TextDraft` keep Swift's fields. A `LayerText` holds its image's `ImageIdentity`, as a `LayerShape` does; `ImageLayer.text` joins equality and `liveText()` compares identities. TextKit has no Linux twin, so `Rendering/TextLayout` is Linux-only: `TextLines` lays a style out with `QTextLayout` as `textBoxSize` and `textImage` lay it out with TextKit. Lines have a fixed `lineHeight` with the baseline at their bottom, so extra leading sits above the letters (Swift's equal minimum and maximum line heights); they wrap at word boundaries, a word longer than the line anywhere (`byWordWrapping`); a line that would pass the container's bottom is not laid, nor anything after it (`overflows`); a final newline adds no line to a measure (its line holds the caret alone, 8.9b), and an empty paragraph lays one, the caret's room. Paragraphs part at Cocoa's separators, LF, CR, CRLF and U+2029, and Qt breaks a line at U+2028 by itself. Tabs stop every 28 points, as `NSParagraphStyle`'s twelve default stops do up to 336. Past the twelfth Cocoa has no stop and moves a tab down a line (a line of tabs wraps after 336 points in an `NSTextView`); here the stops go on every 28 points (known difference): moving such a tab down would lay the rest of its paragraph again for each one, quadratic in a run of tabs, and measure bidi lines by hand, while `QTextLine::setNumColumns` leaves the tab hanging on the line above. Faces go by PostScript name, as macOS names them: fontconfig lists each installed face's `FC_POSTSCRIPT_NAME` with its family and style (`availableFonts`, the bar's list). A name it does not list is Qt's match for that family, where Swift falls back to the system font; fontconfig's aliases put Helvetica, the default, on a metric twin where one is installed. The size is the style's in pixels, as a CoreGraphics context counts points, rounded: Qt draws a face in whole pixels (`QFontPrivate::engineForScript` rounds a point size's pixels too), so a fractional size draws at the nearest whole pixel where CoreText draws it exactly (known difference; the default is whole, and the bar's steps keep a whole size whole). Kerning is off, since Swift always sets `.kern`; tracking is absolute letter spacing after every letter, the last included, as CoreText kerns; hinting is off, so Qt lays out design advances by itself (`QFontEngineFT::shouldUseDesignMetrics`) and the layout sets no flag for them. Qt 6.4 scales absolute letter spacing by the device's dpi over its own in whole numbers, so on a 72-dpi image it vanishes (probed): lines are laid out without a device, where that scale is one. Letters differ from macOS's where the faces differ; the rules are the same. `Dockerfile.dev` installs `libfontconfig-dev`; CMake links `Fontconfig::Fontconfig`. In the session `textDraft` has a public setter, as Swift writes it freely, and `textDefaults` a getter. `applyText` takes its draft by value, as Swift's struct is passed: `finishText` hands it the session's own draft, which it clears. It clears the draft first (the gates read it) and puts it back on refusal, silently, and before an error is announced, so the error's signal sees the draft; blank new text and an unchanged edit close the draft, announced, with no step and no canvas focus request. `layerName` keeps 40 graphemes (`QTextBoundaryFinder`), Swift's `prefix(40)` of Characters; `simplified()` makes whitespace runs one space. `recolorText` logs a failed redraw where Swift's `try?` is silent. Left out as dead: the `isFinite` terms of `isValid` and `boxIsValid` (the ranges refuse NaN and infinities); the draft and document guards of `beginText`, `editActiveText` and `recolorText` (`canEditLayers` reads both); `textBoxSize`'s `max(16, …)` on both sides (the padding alone makes 24) and its caret line (an empty paragraph lays a line); `textImage`'s `width >= 1` terms; `recolorText`'s validity guard (`textImage` refuses an invalid style, and the refusal is logged); `setPaletteColor`'s Type-tool test (a draft lives only under the Type tool: every way in sets the tool, and a switch finishes text first); `fillSelection`'s `liveText` test (`recolorText` asks it); the store rule's folder term (text needs pixels, and `LayerHierarchy::validate` refuses a folder that has them). Hooks: the gates and `canStartProjectOperation` read `textDraft`; `selectLayer`, `selectLayers` and `selectTool` finish text first when the choice changes, and stop when that is refused; the foreground swatch colours an open draft; Fill recolours live text when neither a selection nor a mask is in play; `addPixelLayer` takes the style, as it takes a shape's; `installProject` loads text and `applyDocumentSize` does not; the record carries live text; every rebuild that drops a shape drops text; the canvas resizer passes it on, the image resizer not. The manifest's `text` is Swift's `Codable`: every key required but `boxSize` (synthesized decoding ignores the defaults), the alignment by raw value, the box as two numbers; the store refuses a project whose text fails `isValid` or has no pixels (Swift's `validate`; its adjustment term is dead, since an adjustment layer's own rule refuses pixels, 9.5a), and a snapshot installed past the store loads such text as pixels (`LayerText::loaded`). `TypeControls` is the tool's `ToolHeaderBar`: the face as a `TypeFontPicker` (since 12.1: its list of fontconfig's names and the style's own, sorted, loads when the menu first opens); size, tracking and leading as `TextStyleField`s, `QLineEdit`s that take each readable edit as Swift's value bindings do, show the session's number unless focused, step by one on the arrows (Shift ten), keep their typing while a menu or popup borrows the focus, and keep the focus on Return, showing the number again, selected, as an `NSTextField` does: Swift's Type bar alone has no `releasesFocusOnCommit`; Escape is the field's own. They print Swift's `.number`: at most three decimals, none trailing; digits are not grouped, as in every field of the twin. The size's parse check is left out: text that is no number reads as zero, which no size passes. The size steps within 1–2000; the leading shows Auto as its placeholder, clamps what is typed to 0–5000 and steps from the height Auto works out to. The alignments are checkable `QToolButton`s with Swift's `text.align` glyphs drawn as paths, redrawn on `PaletteChange` as the Move bar's lock is; Cancel and Done show while a draft is open, else Edit Text, enabled on live text; the bar rests without a document or while busy shows. The fields scroll as the Move tool's do. The colour swatch and `openTextColorPicker` came with 8.10a. A live text row in the panel shows the rail's Type glyph 1.2 times up, centred (Swift's `textformat`, 1.21 times up), "Editable text layer", "Select text: " and "Text" (Swift 1.1.5's words); `ThumbnailKey` carries `editableText`, so text that loads as pixels redraws. A double click on a control makes the row active, then opens its text (Swift's `renameClickedLayer`); on the name it renames. The inline editor, the canvas's gestures and the edited layer hidden under its draft come with 8.9b. Equivalent mutants: `ImageLayer`'s equality without its text term (every text change brings new pixels); `TextLines` without its stop after a paragraph that overflowed (every later paragraph overflows at once, so the stop spares only their layouts).
- The inline editor (8.9b): `Rendering/InlineTextEditor.h/.cpp` twin Swift's file; `InlineTextEditor+Editing.cpp` holds its text view's keys, moves and undo, `InlineTextEditor+Input.cpp` its input methods and clipboard. Swift's editor hosts an `NSTextView` that AppKit turns and mirrors with the layer; a Qt child widget cannot turn, so the canvas paints the editor itself, as it paints `TransformOverlay`, and hands it its keys and input methods, and what `NSTextView` gives for free (selection, typing, deletions, movement, undo, the clipboard, marked text) is written here on `TextLines`, the layout `textImage` draws. `synchronize` follows Swift's: the logical size is `textBoxSize`, point text on a layer grows by the width's factor with its corner kept, handles are six view points (two at least), a style changed elsewhere clamps the selection unless text is marked, and a fresh draft clears the undo steps and takes the keys, posted, unless a text field (`QLineEdit`) holds them. The canvas synchronizes on every `changed()`, so a draft that ends takes its editor with it; Swift's `fresh` branch is reached here only when the session's `setTextDraft` sets one draft over another, as SwiftUI's coalesced updates reach it, and a test does that. The box maps layer pixels through the layer's unit square without flips; the text surface mirrors about its middle. The frame (accent, a sixth of a handle wide, inset a twelfth), the eight white handles with accent rims and the black overflow plus draw first and the text over them, as a subview draws over its view; the caret is a unit wide and a line tall in the text's colour, shown with an empty selection while the canvas has focus, blinking at half the system's flash time; a selection is `Highlight`, the inactive one without focus, drawn per line from Qt's own visual runs (a `FormatRange` background, the line's own height stretched to the fixed one), so mixed directions highlight what is selected, and where it passes a line's start or end it runs on to that line's edge on the side the paragraph reads, as TextKit's block selection; marked text is underlined unless the input method styles it. `TextLines` gains `TextRange`, `lineOf`, `caret`, `lineStart`, `lineEnd` (a line that ends short of its paragraph ends before its breaking space, laid next line or not: the caret has no affinity, where TextKit's upstream caret sits after it), `position` and a draw with a selection and marked text; it flags overflow only when a character is left unlaid, TextKit's glyph test, so an empty box shows no plus. After the text's final break (LF, CR, U+2029 or U+2028) it lays TextKit's extra line for the caret, even past the container's bottom (point text's measure, `boundingRect`'s, leaves it out), so Home, Up and typing there stay on it; measures and overflow ignore it, and the editor's repaint reaches a line below the box. A U+2028 that ends any paragraph gets the empty line Qt's own `createLine` makes after it, as TextKit breaks there, and a line ends before the space or separator that breaks it. A position past the laid text has no line (`lineOf` is empty past `m_laidEnd`, where Qt's `lineForTextPosition` would answer the last laid line for a paragraph's end): there the caret hides, Home and End go to the text's start and end, and Up and Down stay put. Keys: Swift's own (Escape cancels, Alt with the arrows sets spacing, Ctrl+Return finishes), the fills' text meanings (Alt+Backspace and Alt+Delete a word, Ctrl+Backspace and Ctrl+Delete to the line's start or end; Shift adds nothing, as `NSTextView`'s Shift-Delete deletes back, and the keypad's Delete deletes), then Qt's standard keys for undo, redo, the clipboard, select all and movement, as the app's text fields take them; X11 binds Alt+Backspace to Undo and Shift+Delete to Cut, so deletions come first and Shift+Delete stays Cut. Return types a newline, Tab a tab, and typing is what `QInputControl::isAcceptableInput` accepts, term for term (a format character before the Ctrl test, AltGr's Ctrl with Alt typing). Characters are graphemes and words `QTextBoundaryFinder`'s; in a paragraph that reads right to left (its first strong letter, as Qt judges), Right goes back and Left on, words alike, and a plain arrow collapses a selection to its own side, as Qt's fields move in their logical style; Up and Down keep their first x and reach the start or end past the lines. Undo is the editor's own stack: typing and deleting each coalesce until the caret moves, paste and cut are steps of their own, and a fresh draft starts empty (Swift's `removeAllActions`). Marked text lives in the draft's content, as `NSTextView` keeps it in its storage, but history follows Qt's input method contract: the preedit records nothing, and what commits or removes text makes a typing step from the text before the preedit (joining a typing run, else its own), so a cancelled composition keeps the redo and undo while composing takes the last step back. Each event follows `QWidgetLineControl::processInputMethodEvent` on the text without the preedit: input (a commit, a changed preedit, a replacement) takes the selection first, then the replacement counts from the cursor, a range removed whole or not at all, a zero length inserting at its offset, and where nothing commits the cursor goes where Qt leaves it; an event that is no input changes nothing (Qt's fields remove a selection only on input, and ibus sends empty preedits when an engine switches modes). A `Selection` attribute sets the selection after the commit; while a preedit shows, that selection stays beside it (the preedit's `anchor`, in the text without it), drawn and answered to queries, until the next input takes it, and the attribute ends a typing run as a move does; a draft set over a composing one ends the composing; `TextFormat` attributes style the preedit, counted from its start (a format that is none is passed over, as Qt's fields do), else it is underlined; a `Cursor` attribute places the caret, hides it at length zero and colours it with a `QColor` value. Copy, Cut, Paste and Select All, from the menu or their keys, work around a preedit as Qt's fields do: on the text without it and the selection beside it (`plain`), the preedit then going back at the cursor (`settle`), so Select All then a commit replaces everything; undo takes a preedit away with the step, since it records nothing. Other keys reach the editor while a preedit shows only when the input method lets them through, and act on the text as it stands: typing and deletions end the composing, the preedit staying as text, as NSTextView unmarks it. Text holds 100,000 UTF-16 units (`shouldChangeTextIn`). The canvas makes the editor in `synchronizeDisplay` (Swift's `synchronizeInlineText`, whose twin lives in `InlineTextEditor.cpp`), skips the edited layer in `drawOwn`, the editor's repaints covering its box while it is edited; a draft that begins, ends or is replaced repaints the whole canvas, as Swift's `needsDisplay`, because the editor's box need not cover the layer's (text shrunk while edited, a layer stretched one way, which point text shows at its width's scale); while a draft is open every key goes to the editor (a key it leaves goes on to `QWidget::keyPressEvent`, which ignores it for the ancestors, none of which takes keys: its mutant is equivalent; so is the blend keys' focus term, since `canEditLayers` refuses a blend step while text is open), the text view's standard keys and Backspace with any modifier (the fills' keys; Delete has no menu key and needs no claim) win `ShortcutOverride` ahead of the menus, Shift+Tab stays put, focus shows and hides the caret (its blink is `caretBlink`, a named child timer of the canvas, running only with focus, so tests read it), input methods are enabled through `setAttribute` alone (Qt updates the input method itself and commits a preedit on the way out, so the editor goes first and that commit finds none) and follow the caret: every edit, move and view change updates them while the canvas is the focus object, as `QWidget::updateMicroFocus`, and a focus request leaves the keys where they are, as Swift's `consumeFocusRequest`. The menus follow Swift's text branch: with a draft open Undo and Redo are bare and enabled, and Undo, Redo, Cut, Copy, Paste and Select All reach the editor of the focused canvas, a text field's first. The pointer (placing the caret, dragging a selection, the handles, the text box, the cursors) comes with 8.9c.
- The pointer on open text (8.9c): `InlineTextEditor+Pointer.cpp` holds the pointer half of Swift's file: the canvas's text gestures (the `CanvasView` extension there: `beginTextGesture`, `dragTextGesture`, `finishTextGesture`, `drawTextBoxDraft`) and what the editor view and its `NSTextView` do with the mouse. A Type-tool press goes to the open editor first (`press`, Swift's `hitTest`): a handle's band (Swift's `handle(at:)`: ten points to a six-point handle, a third of the box at most) resizes; a press inside the box but in the text's padding does nothing, as Swift's editor view; inside the text it is the text view's click; elsewhere `beginTextGesture` finishes the open text, then opens the topmost visible live text under the point, its click forwarded to the text view wherever it lands (`pressText`, as Swift forwards `mouseDown`), or starts a box. A release under four pixels both ways is point text, else `beginText(in:)`; Escape (ahead of the editor's keys) and another tool drop the box, drawn a point wide in the accent, last; QPainter strokes a one-point pen without joins (its cosmetic stroker, probed), so the box's four outer corner pixels stay clear where CoreGraphics' miter covers a quarter (known difference). Swift's `needsDisplay` at the end of `beginTextGesture` is left out as dead: opened text repaints the canvas, and a box of no size draws nothing until its drag repaints it. A box whose document goes mid-drag (an undone New Canvas) draws and drags nothing and makes nothing on release, Swift's guards in `dragTextGesture` and `drawTextBoxDraft` (the twin's in `textBoxDraftRect`, which both read). Clicks follow `NSTextView`: one places the caret at the nearest position, two select the word under the pointer (`QTextBoundaryFinder` words; the character under it by `CursorOnCharacter`, `TextLines::character`), three the paragraph with its break, and a drag extends by the click's unit from the unit it began on, only while the left button is held. Above the lines is the text's start and below them the end of the laid text, where `NSTextView` puts a click or drag past its lines. An empty last line has no word or paragraph (the unit is empty there, where a lookup at the last character took the line before); past the text's end a double click takes its last word. Shift extends by the last click's unit (`NSTextView`'s kept granularity, `QWidgetTextControl`'s double-clicked word) while the selection that click made stands: its press drags on from that unit, and a selection set otherwise brings the caret's own unit back, extending from the anchor: keys, and any change of style or text, since Swift's style sync sets the selection anew (`setSelectedRange`, which resets the granularity); a fresh draft of the same style keeps it, as Swift's. The row under the pointer is judged as a double before it becomes an `int`: a far drag over a squashed layer passes `int`'s range. Qt has no triple click: the press right after a double click counts three when it comes within the double-click interval and the drag distance, as `QWidgetTextControl` times it; a press elsewhere ends the wait, as AppKit counts each click from the one before. Clicks map through the text's own mirror, so the caret lands where the letters show; Swift's `NSTextView` takes them unmirrored, because AppKit's hit testing ignores the layer transform that mirrors it. A click while a preedit shows asks the input method to commit, Qt's rule for a moved cursor (`QInputMethod::commit`, a no-op offscreen, so the call and the guard before it are equivalent mutants there), and lands the preedit as typed if none does, as `NSTextView` unmarks. A handle's press makes point text a box of the size it shows (Swift's `mouseDown`, whose `fixed.origin` is left out as dead: new point text shows at its own origin, and text on a layer commits its transform); its drag sets the box in its own turned frame, 16 source pixels a side at least, rounded, the far edges kept, and refuses a box or transform that is not valid. The cursor over a band is the frame's resize cursor turned with the box by eighths (Swift's `handleCursor` on Qt's four resize shapes; the rotation is reduced by 360 before the eighths are counted, since Swift's `Int` holds turn counts an `int` cannot), the I-beam elsewhere; a resize keeps its cursor, and its release shows the one under the pointer, as every release on the canvas does. AppKit always sends `mouseUp` to the view that took `mouseDown`; Qt can lose a release (a popup or modal dialog opened mid-drag, a grab the compositor takes), so a move without the left button, a lost focus or the next press ends a text gesture: a box being drawn goes, repainted away, and a selection or resize stops where it is. An edit (typing, an input method, undo, the spacing keys) ends a drag or a resize as a press would: Swift's resize would write back the draft it began with, dropping the edit, and AppKit's tracking loop holds a selection drag's keys until the release (known differences, the first a fix). Equivalent mutants: `drawTextBoxDraft`'s save, restore and brush (it draws last, on a painter each overlay before it restores) and its guard (no box maps to a null rect, which draws nothing). Known differences: `NSTextView`'s context menu and its dragging of selected text are AppKit's own; the Edit menu carries Cut, Copy and Paste. `arrowPath` and `duplicateCursor` moved to `EditorCanvas+Cursors.cpp`, keeping the navigation file under 500 lines.
- The palette and its picker (8.10a): `Document/ColorPalette.h/.cpp` twin Swift's file. `PaletteColor` gains `quantized`, `hex` and `fromHex` (Swift's `init?(hex:)`): spaces and tabs trimmed as Swift's `.whitespaces` trims them (Unicode space separators and the tab, never a line break), one leading `#`, three digits doubled, six required, then Swift's `UInt32(_:radix:)` read by hand: an optional sign, a minus holding zero alone, no `0x` (Qt's `toUInt` takes `0x` and white space). `PickerHSB` keeps Swift's maths to the letter (`fmod` for `truncatingRemainder`, `Int(h)` truncating) and its `setRGB`: grays keep the hue, black the saturation. `ColorPickerTarget` is a struct with a `Kind`, as `TransformDrag::Mode` twins an enum with payloads: the palette and text, the Gradient Map's ends since 9.4a, an effect's colour with 9.6. `ColorPickerState` is a plain struct in the session with an `id` for Swift's object identity (a new picker opens its panel anew); Swift's unused `background` and `PaletteColor(NSColor)` are left out. The sheet writes the working colour through `setColorPickerHSB`, which notifies, where Swift writes `colorPicker.hsb` in place; `closeColorPicker` clears the picker before applying it, so each signal sees it closed. `sampleCompositeColor` draws the live composite into one premultiplied pixel at the floored point and undoes the premultiplication as Swift does; a composite that throws logs on `omaphoto.app` and samples nothing. `UI/FloatingPanel` is Swift's `FloatingPanelController`, brought forward from 9.1: a `QDialog` with `Qt::Tool`, non-modal as a dialog is unless asked, fixed to its content's size, remembering its top-left by name for the run: every show and every move while shown remember it, so a panel dropped without closing keeps its place and a close has nothing to add (Swift's `close` and `windowWillClose` remember again); first shown over the canvas's middle (the owner window's `CanvasView`), else centred on the window, as a `QDialog` centres itself on its parent; a shown panel keeps its place, since Qt keeps a window's top-left as its size changes where AppKit keeps the bottom-left (Swift's re-pin has no twin); every show raises it and hands it the keys, Swift's `makeKeyAndOrderFront`; its close button and Escape report through `onClose`, as `windowWillClose` does, and `close` hides without reporting (Qt's `hide` sends no close, so Swift's `dismissing` has no twin); `refocus` activates the shown panel of a name; new content is shown at once, so the panel takes its size at once (a layout shows late children from the event loop), and old content is hidden at once and deleted later, since a signal from it may still run (the layout lets it go then). `QDialog::closeEvent` would reject, and so close, again: the panel's close accepts directly. Known differences: a Wayland compositor places windows itself, so the remembered places hold on X11; `hidesOnDeactivate` has no Linux twin. `UI/ColorPickerSheet` twins Swift's file: the 256-point field (white to the hue across, clear to black down, a 60% black frame, the marker's black ring behind its white one), the hue strip (360 on top, arrows in the text colour), the preview (a 60% black rim), OK as the default button and Cancel, the R, G, B and hex entries and "Click the canvas to sample" (sampling arrives with 8.10b). The field and the strip pick with the left button alone, as SwiftUI's `DragGesture`. The strip's arrows reach five points past its ends, as SwiftUI lets them overflow; a widget clips its painting, so the sheet draws them over the strip's place and repaints that room. Every control carries Swift's accessibility label as its accessible name (Saturation and brightness, Hue, New color, Red, Green, Blue, Hex color) and every entry Swift's title as its placeholder; Qt's plain widgets hold no settable accessible value, so the hue's rounded degrees are the strip's description. The entries are `PickerField`s, committing on Return and on leaving, where a menu or popup borrowing the focus keeps the typing; an entry keeps its typing only while it holds the keys and was typed in, and a pick on the field or the strip, which take no focus, replaces the channels' typing (9.6f): a channel takes digits alone, clamped as Swift's binding (an overflow reads as 255, an empty or untouched entry changes nothing), Up and Down stepping one, or ten with Shift, from the colour's own value; the hex commits on every leave, as Swift's `onChange(of: hexFocused)`, which snaps the working colour to its 8 bits. Return in an entry commits it and goes on to OK, since a `QLineEdit` passes Return to its dialog; Escape cancels. The channels are made before the hex entry, so the focus chain reads the grid and the keys start at R, which follows the colour until typed in; the hex entry follows only while it lacks the keys, and holding them first it would put its old text back on leaving. `ColorPickerPanelController` shows a new sheet per picker, titled by its target; its close button cancels, and Swift's guard there is left out, since closing no picker does nothing. `UI/ColorPaletteControls` twins Swift's file under the rail: two 24-point swatches (a 1.5 white ring inside a black rim), the swap (X) and defaults (D) glyphs drawn as paths in the secondary ink, dimmed while disabled, the whole resting while the palette cannot be edited, both swatches repainted whole on every change (they overlap); a mask's swatch offers Black · Hide or White · Reveal in a popup under the swatches (Swift's popover), which a change of target closes, and a mask chosen cancels an open picker; the panel follows the session's picker by its id. Swift's frame is 36 points and its two buttons reach 3 points past it, so the twin's widget is 42 points square with the frame inset by 3, in a rail column 42 wide with the tools centred, the swatches 18 points below the last tool (Swift's spacing of 10 and padding of 8). `SwatchButton` draws every swatch: the palette's (radius 6, white ring 1.5), the Brush bar's (34 by 18, radius 4, white ring 1, black rim), the Shape bar's Fill and the Type bar's (36 by 18, radius 3, a half-black rim). The Brush bar's shows the foreground for the Brush and Spot Healing, not Clone Stamp, the Smear or a mask, resting while the palette cannot be edited; the Type bar's shows `typeColor` and opens `openTextColorPicker`. X and D swap and reset the palette on the canvas and in the list, Shift allowed, not with Ctrl, Alt or Meta; `ProjectWorkspace::canSwitch` refuses while a picker is open. Tests wait for the panel to take the keys (`QApplication::activeWindow`): a tool window reads as active whenever its parent is, and offscreen a hidden panel stays the focus window, where a window manager hands the keys back. Equivalent mutants: `raise` (offscreen keeps no stacking order), `refocus`'s `isVisible` (offscreen activates no hidden window), `show`'s `wasVisible` guard (a shown panel stands where it was remembered), and in `sampleCompositeColor` Swift's `min(alpha, value)` (a premultiplied channel never passes its alpha), `painter.end()` before the read (the raster engine writes at once) and the warning.
- The Eyedropper and picking (8.10b): `EditorCanvas+Picking.cpp` holds Swift's sampling. `palettePicking` is the Eyedropper, or Alt with the Brush, Spot Healing or the Gradient while no stroke runs and no gradient end is dragged; `picking` adds an open picker (the Levels and hue sample modes arrive with 9.1 and 9.3). A press while picking, Space aside, samples at once and keeps the colour it began from; a drag samples on; the release ends it and, with a picker open, hands the picker the keys back (`ColorPickerPanelController::refocus`, which the canvas includes, as Swift's calls it). `sampleColor` samples into the open picker, else sets the foreground through `setForegroundColor` while the palette can be edited (a chosen mask too, as Swift sets `foregroundColor`), and rings the point. Qt can lose a release: a move without the left button, a lost focus or the next press ends a sampling. Picking outranks every tool's press, a double click (the second click is a press, so the inline editor and a polygonal Lasso stand aside while the picker is open, Swift's `hitTest`), a hover with no button held (the eyedropper alone: the brush circle neither moves nor shows, as Swift's `mouseMoved` returns first; a right-button drag still sizes the tip, as Swift's `rightMouseDragged` ignores picking) and the cursor (after the drag cursors, before Space). `syncPicking` ends a sampling when picking begins or ends: `synchronizeDisplay` runs it, as does every modifier change (Swift's monitor), a sampling press before it begins (Alt may first show in the press, and the foreground's signal would otherwise end the new sampling) and every move (Alt let go unseen). `pickingRelease` returns nothing, where Swift returns from `mouseUp`: a sampling press begins no other gesture, so the rest of the release finds nothing to end. `SampleRingOverlay` is no widget, like `BrushCursorOverlay`: 116 points round the pointer, a 24-point ring of gray 0.45 under a 16-point one, the sampled colour on the top half and the original below, each half replacing the clip and one restore dropping it, drawn over the overlays and under the inline editor; `showsSampleRing` (a getter and a setter that notifies) hides it. The Eyedropper's bar is Swift's inline one, built in `ContentView`: the title and a "Sample Ring" `QCheckBox` 16 points on, following the session under a `QSignalBlocker`. `eyedropperCursor` draws the symbol into Swift's 20-point box of a 24-point image, sixteen white offsets of 1.25 and then black; its hot spot is the drawn tip, (5, 19), as Swift's (3, 21) is its symbol's tip. The glyph is `Rendering/EyedropperIcon`, which the rail and the cursor share, as they share `SelectionIcons`. A mounted canvas leaves the keys to an open picker (Swift's `viewDidMoveToWindow`). The application event filter moved, unchanged, beside the modifier helpers in `EditorCanvas+Cursors.cpp`, keeping the navigation file under 500 lines. Equivalent mutant: the ring's `setBrush(Qt::NoBrush)` (the painter reaches it with no brush).
- Levels in the session (9.1a): `Document/Levels.h/.cpp` twin Swift's file, `Levels+Session.h` its session half; `LevelsAutomatic.h/.cpp` and `LevelsAutomatic+Session.h` the other file. `LevelsPixels.c` compiles in place beside the other kernels. `LevelsChannel`, `LevelsSample` and `LevelsAuto` keep Swift's raw values (`rawValue`) and case order (`allLevelsChannels`, `allLevelsSamples`, `allLevelsAutos`); `LevelsSample` is declared opaquely in `Levels.h`, since `LevelsEdit` holds one, and defined with the automatic levels, as Swift's. `LevelsSettings::sampling` is declared in `Levels.h` and defined in `LevelsAutomatic.cpp`, as Swift's extension; `settings(mode, histogram)` stands for `LevelsAuto.settings(histogram:)`; `setCurrent` is Swift's `current` setter, storing the range normalized. A histogram is `LevelsHistogram`, four arrays of 256 bins where Swift has `[[Double]]`, and `LevelsHistogramDisplay::scale` takes one channel's bins. `LevelsFilter::run` leaves soft edges to the kernel. Swift's cc5aac4 once unpremultiplied each soft edge before `levels_apply`, which unpremultiplies again; Swift agrees with the twin since 1.2.0 (`f6a74c9` removed that pass), and its `inputClippingGammaOutputInversionAndAlpha` holds (64, 96, 128, 128) as the twin does. The histogram hands the kernel one row at a time with the mask's own row, since Qt pads a gray image's rows and the kernel accumulates; neither it nor the filter's tables take heap memory of their own, whose failure would throw `std::bad_alloc` past the worker's catch. `LevelsEdit` is a plain class in a `std::optional` of the session, like `FilterEdit`, its `id` standing for Swift's object identity; past 8000 pixels a side its preview source is a scaled copy (sides truncated, one pixel at least), drawn from a painted layer's tiles without flattening them. The session keeps a watcher each for the histogram, the preview and the commit, with the edit each serves: where Swift cancels a task, the twin forgets whose it is (`m_levelsPreviewFor`; a histogram needs no token, since a new edit's count replaces the watcher's future, whose signal Qt then drops), so a result for a turned-off, closed or committing edit drops; one preview runs at a time, the newest job waiting, and a commit drops the waiting job too. A run counts as running until its finish has run (`m_levelsRendering`), as Swift's task clears itself only after its await: Qt's `setFuture` drops a replaced future's pending signal, and `isRunning` and `isFinished` both end with the worker (probed on 6.4.2). A histogram or preview that fails logs on `omaphoto.app` where Swift's `try?` is silent; a failed histogram leaves the bins empty and ready, as Swift's. `setLevelsSampleMode` is the sheet's write (Swift's sheet sets `sampleMode` and bumps `brushRevision` itself); it notifies. The commit writes the layer in place and drops shape and text, as the filter's does. `beginLevels` leaves out Swift's `levels == nil` and its `activeLayer` and `document` guard (`canAdjustColors` reads all three); `hueSaturation` arrives with 9.3, `cancelCrop` with 10.1, the adjustment layer hooks of `updateLevels`, `cancelLevels` and `commitLevels` came with 9.5c. The gates, `canAdjustColors` and `canStartProjectOperation` read `levels`, `selectLayer` and `selectTool` refuse while it is open, and closing it resumes file requests, Swift's `didSet`; the commit's end resumes them through `setIsProjectBusy(false)`, after the edit is gone. `commitLevels` hands its worker the asset, so a painted layer flattens there, where a failure is caught (Swift's lazy image flattens as its task draws). Left out as dead: the display scale's zero-peak guard (with no bin counted the interior is empty too), the preview flag in `previewImage` and in a landing preview (turning it off clears the preview and forgets the run), and in the automatic levels contrast's `low < high` (each channel's low lies below its high, so theirs do), neutral's `0 < mean < 1` and its 9.99 cap (weight at both ends of a range keeps the mean a thousandth inside, so gamma stays under 9.97), and the sample's 0 and 255 clamps (a sample is 0 to 1). Equivalent mutants: the white sample's `max(black + 1, …)` (`normalized` keeps white above black), `sampleLevels`' bounds on the layer's own pixels (a pixel off the image draws clear, which the alpha test refuses), the histogram's `committing` check (a count finishing during a commit, a race no test orders), the commit's check that the layer kept its pixels and place (nothing edits a layer while the project is busy), the tables' reservation and the warnings. `LevelsFailureTests` starves allocations through `AddressSpaceLimit` in a binary of its own: a canvas-wide stroke leaves hundreds of MB free inside malloc's arenas, which `malloc_trim` cannot unmap, so its painted layers are rasters built directly; worker threads allocate within their own reserved arenas, so only asks over 64 MB fail there.
- The Levels sheet (9.1b): `UI/LevelsSheet.h/.cpp` twin Swift's sheet; `Histogram`, `Gradient`, `Track` and `Handle` are private widgets of that file, and the histogram and the tracks follow the session's `changed()` themselves. Each handle is a 22 by 20 widget of its own, a child of the sheet placed over its track, as Swift's `ForEach` makes a view each: a later handle lies on top (white over gamma over black), a press drags only its own, each carries Swift's label, and at either end half of it lies in the sheet's padding, where a child of the track would be clipped. The output gradient is made before the output handles, so they lie on its last row as SwiftUI stacks the later view. A drag reads the pointer along its track, Swift's named coordinate space. The triangle is a path (apex 3.75, base 14.25, 12 wide, Swift's 12-point `triangle.fill`); its half-point gray shadow is a gray rim, since Qt has no blur. The histogram's colours are SwiftUI's gray and, from Apple's HIG for macOS 26 (the Swift target), its dark red, green and blue: (142, 142, 147), (255, 66, 69), (48, 209, 88), (0, 145, 255), data colours like the canvas's grays, whatever the theme. The entries are the picker's `PickerField`s: a number applies on Return or on leaving, as Swift's value binding, other text goes back, and an entry keeps its typing until then, unless its own handle is dragged, which takes no focus and replaces the typing with its value (9.6f); numbers are read and shown in the widget's locale with Swift's decimals, as Swift's `.number` format follows the user's (a German gamma reads `2,5`; no level reaches a thousand, so nothing is grouped). A click on OK takes the focus first, so a typed entry applies before the commit, where AppKit's buttons take no focus and the typing is lost; Return in an entry goes on to OK, the panel's default, as in the picker. The eyedroppers are checkable buttons set from the session, the chosen glyph in the accent and the others in the secondary ink, for Swift's `.tint`, redrawn on `PaletteChange`. The channel picker is named by its label (`setBuddy`): on Linux Qt names a combo box by its label relation, never by `accessibleName`. Alt+P is the Preview box's own shortcut in the panel and the canvas's key when the canvas has the keys. For an adjustment layer's editor the caption says the underlying pixels (9.5d). `ContentView+Panels.cpp` holds `synchronizePanels`, Swift's `onChange(of: levels == nil)`, and since 10.1 the importer and the alerts, because `ContentView.cpp` runs to 500 lines: a `FloatingPanel` named `levelsPanel` shows a new sheet when an edit opens, its close cancelling as Swift's `onClose`, and hides when the edit closes. The canvas draws `previewImage` in the layer's place after a filter's; a press in a sample mode is `sampleLevels` and hands the panel the keys (`FloatingPanel::refocus`); other presses wait for Space, the Hand or the Zoom while Levels is open; Escape, Return, Enter and Alt+P are its keys and every other key but Space passes on; `picking` reads the sample mode, so the eyedropper cursor shows; the application filter's brackets rest. `ContentView::acceptsDrop` needs no term of its own: `canSwitch` reads `canStartProjectOperation`, which reads `levels`. The Image menu's Levels… is Ctrl+L and follows `canAdjustColors` (its `hueSaturation` term arrives with 9.3); Import Images and the New canvas button rest while Levels is open. Undo and Redo are bare, since Levels closes the history, and enabled only while a field has focus, as for a busy project: Swift's bare entries act only on a text view. Equivalent mutants: the histogram's zero-peak guard and its `max(0, …)`, each standing in for the other (with no bin counted, 0/0), its `min(1, …)` (the widget clips a taller bar) and the bars' `+ 0.1` (Qt covers abutting rectangles of one path exactly); the drag's clamp of the tone, white's `max(black + 1, …)` and gamma's `min(0.999, …)` (`normalized` does each); either of a track's move and resize events alone (a layout moves and sizes it together); the canvas's `!preview` before the Levels preview (a filter edit and Levels never overlap); passing an unhandled key on (nothing above the canvas takes keys) and the base `changeEvent` (the sheet paints nothing of its own). Qt sizes the loading note itself: a shown child without a layout is adjusted to its hint.
- Curves and the image adjustments (9.2): `Document/Curves.h/.cpp` and `Document/ImageAdjustments.h/.cpp` twin Swift's files, `UI/CurvesControls.h/.cpp` Swift's view. `AdjustPixels.c` was already compiled for the downsample cache; Curves and Exposure run `levels_apply` from `LevelsPixels.c`, as Swift's do. `CurvesSettings.channels` is a vector of point vectors, as Swift's array, so `isValid` still counts four. `value` finds Swift's `lastIndex(where:)` with a loop; a NaN input takes the first segment at t = 0, as Swift's `max(0, .nan)` gives 0. `ImageAdjustmentPixels::run` hands its body the premultiplied RGBA context `BrushRaster::context` makes and returns that context. `AdjustmentColor` keeps Swift's two initialisers as constructors; the palette's has its callers since 9.4a (a Gradient Map starts from the palette, its picker) and gains 9.5's (new layers), as `normalized` serves the filter's settings since 9.4a and the adjustment's with 9.5; `ends`, which `apply` reads, gains the filter sheet as a reader with 9.4b and returns an `Ends` struct for Swift's tuple. `GrainSettings::apply` takes an optional seed that replaces the stored one and hands the same image back when the amount is 0. Left out as dead: the `isFinite` terms of `AdjustmentColor.isValid` and of the curves' points (the ranges refuse NaN and infinities), and the points' x range (ends at 0 and 255 with x strictly rising keep every x inside). `CurvesControls` takes Swift's binding as a value and a change function and shows the settings on `synchronize`, which each of its own edits calls and its owner will (9.4's filter sheet); a channel shown anew drops the selection and the drag, Swift's `onChange`. The graph (`curvesGraph`) is a private widget 260 tall: black at 35%, white quarter lines at 12%, the curve two wide, 8-point dots with the chosen one in the accent; presses and drags follow Swift's gesture (a point within 14 curve units is taken, else one is added between x 1 and 254, more than a unit from the others, 32 at most; an inner point keeps a unit from its neighbours; the left button alone). Remove point keeps Swift's guard (an inner point that is still there), so a selection another change has left behind removes nothing. The readout (`curvesReadout`) truncates as Swift's `Int(…)`; SwiftUI's `monospacedDigit` has no Qt 6.4 twin (font features arrive in 6.6), so the digits are the font's own. Carried from 9.1b's review: the Type bar's size and tracking read and print through its locale, as Swift's `.number` fields, without group separators, as every field of the twin; leading keeps `Double(text)`'s period, as Swift's. Equivalent mutants: the curves' `2…` lower count (one point cannot hold both ends), `<` for `<=` in the segment search (the curve is continuous at its points), `< 0` for `<= 0` in the inner slope (a zero slope's reciprocal is infinite, so the harmonic mean is zero anyway) and the final 0…255 clamp (Swift's slopes never overshoot a valid curve); Exposure's `max(0, …)` before the gamma and its table's lower clamp (a negative light ends at zero either way), the gradient map's byte clamp (its colours lie in 0…1); the controls' `x > 1` and `x < 254` (a point more than a unit from both ends lies inside them) and Remove's upper bound (Remove rests on the last point).
- Hue/Saturation in the session (9.3a): `Document/HueSaturation.h` twins Swift's types. Swift's file runs to 574 lines, so the twin splits it: `HueSaturation.cpp` (ranges, bands, sample modes, settings, the edit), `HueSaturation+Filter.cpp` (the cube) and `HueSaturation+Session.cpp` (the session extension, `canAdjustColors` with it; `HueSaturation+Session.h` its fragment). `ColorRange` and `HueSampleMode` keep Swift's raw values and case order (`allColorRanges`, `colorRanges`, `allHueSampleModes`); `defaultBand` is a free function where Swift has a property, and `help` gives the modes' help; their SF Symbols, the eyedropper and its badges, are the sheet's to draw (9.3b). `HueSaturationSettings` keeps Swift's dictionaries as `std::map`s, so the constructor's entry for its range and the setters' inserts compare as Swift's do; Swift's computed `hue`, `saturation`, `lightness` and `band` are getter and setter pairs. `HueSaturationFilter` is a namespace; `HueResponse` and `Color` stand for Swift's tuples, and `cube` returns the floats Swift packs into `Data`. Core Image's `CIColorCube` becomes a CPU lookup, rows in parallel: each pixel unpremultiplied, read trilinearly from the 33-point cube, premultiplied again and rounded once; Core Image's own precision may differ by a level, and Swift's tests allow eight. A failed table or row allocation is `ExportError(render)`, since a worker's `bad_alloc` would pass its catch; `HueSaturationFailureTests` reaches that net through a picture one pixel wide, whose row list asks as much as its pixels. A selection blends the result over the job's own pixels, as the Levels filter does, where Swift draws them into a context first: the same bytes, since layer pixels are that context's format. `HueSaturationEdit` is a class in a `std::optional`, as `LevelsEdit`, its `id` standing for Swift's identity; its preview source is made as the Levels edit's (to 8000 pixels a side, from a painted layer's tiles without flattening). The session keeps a watcher for previews and one for the commit. Where Swift cancels the preview task (Preview off, nothing to show, OK) the twin forgets whose it is, so that result drops; a result for a closed edit fails the id check, Swift's `hueSaturation === edit`. A run counts as running until its finish has run (`m_hueSaturationRendering`, as Levels' queue), so a failure is reported even when the next job waits. Known difference: Swift's run for a closed edit returns before it looks at the queue, so a job queued behind it waits for the next change; the twin's runs it. Known difference: Swift's task never looks at its cancellation, so a render still running when Preview goes off, or when OK is pressed, lands. A failed render sets `brushError` whichever edit asked, as Swift's `adjustedPixels` does. Known difference: Swift's `beginHueSaturation` resolves a pending gradient without waiting, so its edit holds the pixels from before the gradient and the commit, finding the layer changed, lands nothing; the twin waits for the gradient, as `beginLevels` does. `commitHueSaturation` refuses while a commit runs (Swift has no guard; its second commit would find the layer changed and land nothing), keeps a copy of the edit for the finish (`CommittingHue`), frees the project before the edit goes (Swift's two `defer`s) and names the new asset after the layer; the rebuild drops shape and text. `sampledHue` reads the composite through `PickerHSB`, as Swift's; `beginHueTargeting` takes Swift's `max(by:)`, the first of the strongest claims. `setHueSampleMode` and `setHueTargeting` are the sheet's writes and notify on a change; `endHueTargeting` changes nothing observable and stays silent. Swift's beeps are warnings on `omaphoto.app`. Left out as dead: `beginHueSaturation`'s `document` and `activeLayer` guard (`canAdjustColors` reads both) and the targeting's `?? .reds` (the ranges are never empty). Equivalent mutants: the weight's fallbacks for ramps of no width (no hue lies inside one) and its `<=` at the plateau's end (both sides give 1); `toHSL`'s cap on saturation, `toRGB`'s gray return and clamp (the arithmetic stays within 0 and 1 but for rounding, which later clamps absorb); a clear pixel's fill (its lookup is multiplied by alpha 0); the response's skips of a still range or a zero weight (each adds nothing); the saturation's floor of zero (`toRGB` draws gray at or below it); the amount's clamps and the lightness clamp (a sum past ±100 reaches white or black either way). The hooks: `canEditLayers`, `canContentAwareFill` (so `beginFilter`), `beginLevels` and `ProjectWorkspace::canSwitch` read `hueSaturation`; `canUseHistory`, `canStartProjectOperation`, `selectLayer` and `selectTool` do not, as in Swift.
- The Hue/Saturation sheet (9.3b): `UI/HueSaturationSheet.h/.cpp` twin Swift's file, `HueSaturationSheet` and `SpectrumEditor`; the editor takes Swift's binding as a value and a change function, as `CurvesControls` does. The sheet writes through Swift's `settings` binding (`change`: the settings as they stand, the defaults once the edit is gone, handed over with the edit's Preview). The range picker is a 160-wide `QComboBox`, resting under Colorize; Swift hides its label, so a hidden `QLabel` names it through the label relation Linux reads (there a combo box's own name is its text). Swift's sliders run freely; the twin's step in hundredths and show the session's value under `QSignalBlocker`, clamped to their range, so a typed value past it rests the slider at its end without writing back. Each field is a `PickerField`: a readable, finite number applies when the field lets go of focus (Swift's value binding; Swift's `Int()` traps on the rest, which revert), and Return clamps it to the slider's range (Swift's `onSubmit`), then goes on to OK, the panel's default button, where Swift's handler commits by itself. The field's own slider replaces its typing with the value it sets (a wheel leaves the keys with the field; 9.6f); the others leave it. The fields print whole numbers through their locale, ungrouped as every field of the twin; the unit sits two points past each, the hue's a degree sign, the others empty, as Swift's `unitSuffix`. The eyedroppers and the targeting button paint themselves: a quarter of the accent in a rounded frame when chosen (Swift's plain button with its background), the eyedropper through `EyedropperIcon` at 14 points with an 8-point disc cut by a plus or a minus (Swift's `plus.circle.fill` and `minus.circle.fill`), and `hand.point.up.left` as a finger and a palm outlined and turned; `HueSaturationSpectrumTests` pins each glyph's ink, measured once. The spectrum paints Swift's 72 slices, the after bar through `shiftedHue`, clipped to a rounded rect of 3; its handles are bars for the core and blocks for the shoulders, dragged by nearness round the circle (Swift's `nearestHandle`); the held handle stays until a press starts afresh, because Qt can lose a release, and Swift's `width > 0` is left out (a press needs width). "Limited to the selection" shows with a selection, never for an adjustment layer's editor (Swift's `adjustmentOriginal` term, 9.5d). `ContentView::synchronizePanels` shows the sheet in `adjustmentPanel`, titled Hue/Saturation, while an edit is open; its close button and Escape cancel. On the canvas `picking` counts the hue eyedropper: a press samples the range and hands the panel the keys, unless the colour picker is open or palette picking runs with no range eyedropper armed, which sample colour, in Swift's `mouseDown` order. Targeting shows `Qt::SizeHorCursor` (Swift's `resizeLeftRight`) after picking and before Space; a press begins it and ends there even when refused (Swift returns), a drag moves it by the pointer's x from the press, Ctrl for Cmd driving the hue, and sets the resize cursor again, as Swift's does on every drag, so Alt's eyedropper under the Brush lasts only until the next, a release ends it, and a move without the left button ends a drag whose release was lost; with Space the press pans. A double click with targeting armed is a second press, ahead of the Type tool's words and the polygonal lasso's close, as Swift's `mouseDown` sees it: a text draft and a polygonal outline can both be open under Hue/Saturation (Swift's `canAdjustColors` asks for neither). The press, drag and release live in `EditorCanvas+Picking.cpp` beside the sampling. The canvas draws the edit's preview in the layer's place after a filter's and Levels'. The Image menu's Hue/Saturation… (Ctrl+U) follows `canAdjustColors`, so it stays enabled while its own edit is open, as Swift's (choosing it again changes nothing); Levels… rests meanwhile. In a text field, on a desktop whose keyboard scheme binds Ctrl+U to deleting the line (X11's), the field takes it first, as with Ctrl+A; offscreen binds nothing, so the tests see the menu. Equivalent mutants: the top row's spacing (its stretch takes the room), the slider's stretch (a horizontal `QSlider` expands by itself), `nearestHandle`'s `fmod` (Swift's too: the handles and the pointer lie within one turn) and `endHueTargeting` on release (the canvas never reads the drag it clears). A buttonless move never reaches the handles (Qt drops it without mouse tracking), so their left-button check is tested with the right button held.
- Filters in the session (9.4a): `Document/Filters.h/.cpp` hold Swift's model (Remove Background's kind, its four settings, `SubjectRemoval` and `commitBackgroundMask` since 9.7); `isImageAdjustment` and the list of kinds arrive with the Filter menu (9.4b), their only reader. `FilterSettings::normalized` clamps through `ImageAdjustmentPixels::clamp`, a value that is not finite taking the default. `PixelFilter::run` hands Curves, Exposure, the Gradient Map and Grain to their settings' `apply` (Grain in layer pixels, `1 / scale` units, the job's seed), the fill to `ContentFill::run`, and the rest a premultiplied copy, as Swift's contexts: Gaussian Blur is `PixelAdjust::gaussianBlur` unclamped, clear past the edge as Core Image blurs a finite image; Motion Blur is `PixelAdjust::motionBlur`, `CIMotionBlur` on the CPU: Gaussian taps (exp(−i²/2σ²) over three sigmas, normalised) along the angle at σ = distance × scale / √12, each tap read bilinearly with clear past the edge, rows in parallel, the angle counterclockwise on screen since Core Image's y points up; Add Noise and Lens Correction run Swift's kernels, `NoisePixels.c` and `LensPixels.c`, compiled in place (the lens's k is distortion / 100 × 0.35). Known difference: Swift measured Core Image's taper on a dot; the twin's is the exact Gaussian. `FilterEdit::prepare` is Swift's `prepared` and `prepare` in one: the mapping and a preview copy at most 2048 on its long side (sides truncated, one at least; whole for noise, grain and the fill; a painted layer's copy drawn from its tiles, a full-size one flattened as Levels' is). `growForBlur` pads by the blur's reach (3σ + 2, or half the streak + 2) through `grow`, 30,000 a side and 100 megapixels at most (`ProjectError(tooLarge)`), and never shrinks the grid; its rounding up is left out, since `grow` takes the integral box. The session keeps `filterSettings`, which each commit writes and each filter starts from, the Gradient Map from the palette's foreground and background instead. `updateFilter(settings, preview)` normalises, grows the grid when a blur needs more room (a failure is `brushError`; the old preview goes), renders an automatic kind once per settings (`preparedSettings`, which the worker hands back with its image), and with Preview off drops the waiting job and the preview. Known difference: one watcher serves every edit, so a job may wait behind a cancelled edit's run; that job is Swift's running task, and Preview off leaves it (dropped, it would leave `preparing` set for good). `commitFilter` closes a Gradient Map picker with OK first (`cancelFilter` with Cancel), closes as Cancel does with no step when nothing would change (no distortion, Exposure's defaults, no grain), forgets the running preview and drops the waiting job (Swift cancels the task), and hands the worker the job's parts, so a painted layer flattens there; a blur's result is trimmed to the pixels it left, any other keeps the grown grid, and an automatic kind reuses its preview when the settings match. Known difference (a fix): Swift carries a covering mask over the grown box while a trimmed blur's pixels sit on the trimmed box, so the mask slid and squeezed; the twin carries it over the layer's new box. The picker's `gradientMap` target (`ColorPickerTarget::highlights` names the end; the title follows it) opens on the open Gradient Map through `openGradientMapColorPicker`, `previewGradientMapColor` writes the working colour into the map through `updateFilter` (silent when nothing changes), and `closeColorPicker` writes OK's colour or puts the original back, the palette untouched. Left out as dead: the opener's `committing` term (a commit keeps the project busy, which `canEditPalette` reads) and `setGradientMapColor`'s (a commit closes the picker first); that function's other guards came back with 9.5c. `PixelFilter::trimmed` throws `ExportError(render)` when its crop finds no memory, since Swift's `cropping` shares the pixels and cannot fail so; the blurs' row lists (`rowNumbers`) turn `bad_alloc` into `ExportError(render)`, as Hue/Saturation's do, and their weight tables stay plain, the callers bounding them to 1,734 entries. Tests: `FilterTests` (Swift's four; the Gaussian one tests the code, which grows and trims, as Swift's has since 1.2.0, `7c4512a`), `FilterModelTests` (Add Noise and the lens checked against Swift's kernels, whose headers only that test includes), `FilterSessionTests`, `FilterFailureTests` (a binary of its own, under `AddressSpaceLimit`), and in `ImageAdjustmentTests` Swift's two Image-menu tests and the command half of `curvesIdentityAndImageCommandPreserveAlpha` (Swift's `AdjustmentLayerTests` holds it). Equivalent mutant: `>=` in `growForBlur`'s guard (at equal reach it grows the same grid again).
- The filter sheet (9.4b): `UI/FilterSheet.h/.cpp` twin Swift's file, `FilterSheet` and `GradientMapControls`. The sheet is the content of a `FloatingPanel` named `filterPanel`, which `ContentView::synchronizePanels` shows with the edit, titled by its kind, and closes with it, its close button and Escape cancelling (Swift's `onChange(of: filterEdit == nil)`). The kind's controls are made once, since an edit's kind never changes. Swift's `control` is a title (sixty points at least, the slider's buddy), a slider over a thousand steps of its range, or of the range's logarithm where Swift's is logarithmic, the value rounded to the field's decimals as Swift's binding rounds it, and a 56-point `PickerField` with its unit two points after (Swift's `unitSuffix`), which applies a readable finite number on Return or on leaving (normalizing clamps it), gives up its typing when its own slider changes the value (a wheel leaves the keys with the field; a notch that rounds to the same value changes nothing; 9.6f), and shows Swift's `.fractionLength(0...decimals)`: at most that many decimals, none trailing, in the field's locale, digits never grouped, as in every field of the twin. The sliders show the session's number under a `QSignalBlocker`, so a dragged thumb sits at the rounded value, as Swift's binding shows it; a step that rounds to the setting it already holds changes nothing, so the thumb keeps its place and arrow steps add up. Add Noise's distribution is two checkable buttons in a `QButtonGroup` beside its label (Swift's segmented picker), Monochromatic a `QCheckBox`; Lens Correction's note is callout-sized in `PlaceholderText`; Curves hosts `CurvesControls` through the settings. `GradientMapControls` draws Swift's gradient bar (20 high, rounded 4, a 35% black rim inside), the ends as the palette's `SwatchButton`s (24 points, radius 6, a white ring of 1.5 inside a black rim) with their titles, help and accessible names, and Reverse; a swatch opens the picker on its end, and on every change of the picker's colour the sheet calls `previewGradientMapColor` (Swift's `onChange`), which ignores a palette picker. The controls wait for the sheet's first synchronize, which runs once they are built. `settings` and `update` keep Swift's fallbacks for a sheet whose edit has gone: the defaults, Preview on. The Image menu gains Curves… (Ctrl+M) before Levels…, and Exposure…, Gradient Map… and Grain… after Hue/Saturation…; the Filter menu (`Fil&ter`, between Image and Layer, as Swift declares it) lists `allFilterKinds` but the fill and the image adjustments (`isImageAdjustment`), Remove Background among them since 9.7; every entry rests while colours cannot be adjusted or Hue/Saturation is open, as Swift's. Tests: `FilterSheetTests` (7.5's, moved to the panel), `FilterControlsTests` (each kind's controls, the sliders' travel, the fields, the Gradient Map's swatches, bar and repaint), the menus' in `SelectMenuTests` and `CompositorMenusTests`. Equivalent mutants: Swift's `?? .gaussianBlur` for the kind (the panel makes a sheet only for an open edit) and the memory of the picker's colour (`previewGradientMapColor` with an unchanged colour changes nothing).
- Adjustment layers in the document and the store (9.5a): `Document/LayerAdjustment.h/.cpp` twin Swift's file, `LayerAdjustment+Session.h` its session half. `AdjustmentKind` keeps Swift's raw values (`rawValue`, and `adjustmentKind(text)` for the manifest) and case order (`allAdjustmentKinds`); `filterKind` came with 9.5c, its reader; `symbol` names an SF Symbol, whose glyph the panel draws (9.5d). `LayerAdjustment` keeps Swift's fields: the legacy Hue/Saturation four, the optional `hsvSettings`, Levels and Curves, and the optional Exposure, Gradient Map and Grain, whose computed properties are getter and setter pairs; `resolvedHSV` falls back on the legacy four. `isValid` keeps Swift's bounds (hue within 360 either way, the rest within 100, each range's values alike, every band's handles finite, Levels as normalized, then every kind's own rules whatever the kind) and leaves out the `isFinite` terms the bounds already refuse and Levels' count (the twin holds four ranges). `apply` arrives with 9.5b, its reader. `ImageLayer.adjustment` joins equality and travels wherever Swift lists it: the record (`hierarchyRecord`, so the snapshot), `ImageLayer(record, …)` (so an install and a resize's rebuild), both resizers and duplicates. A copy between projects needs no term of its own: the baker bakes nothing for a layer without pixels, and the placement unlinks it, where Swift skips the bake. The manifest's `adjustment` is Swift's synthesized `Codable`, written by hand in `IO/ProjectStore+Adjustment.cpp` over the readers the manifest shares (`ManifestJson` in `IO/ProjectStore+Json.h`): every key required but the four optionals, which stay out when absent; a `ColorRange`-keyed dictionary is an array of key and value in turn, since Swift's `ColorRange` declares no `CodingKeyRepresentable` (a range Swift does not name refuses it, and so does an odd count, whose last key has no value to read, so Swift's count check has no twin; a later pair wins, as a dictionary assigns); the seed is a `UInt32`. The store refuses an adjustment before version 7, on a folder, with pixels or invalid; Swift's text rule's adjustment term is dead, since text needs pixels. `LiveMaskGraph::validate` refuses clipping to an adjustment layer, so `canLinkMask` refuses one as a source; `canPaint` refuses an adjustment layer's pixels, not its mask. `addAdjustment` puts a blank layer named by its kind just above the active one (into an active folder, uncollapsed; Swift's `addBlankLayer` alone lifts a layer above the folder's contents), as one `New … Adjustment` step, a Gradient Map running from the foreground to the background and each Grain with a seed of its own, 10,000 layers at most, then asks for its editor (Swift's `adjustmentEditingID`, 9.5c). `updateAdjustment` writes valid settings alone, with no step of its own, and moves `brushRevision`. Tests: `LayerAdjustmentTests` (kinds, validity, the optionals, the manifest's keys and refusals, the store's and the graph's rules, adding, updating, travel), `AdjustmentLayerTests` (Swift's `legacyHSVStillDecodesAndRenders`; the rest arrive with 9.5b and 9.5c), Swift's `settingsSaveAndOlderAdjustmentsStillOpen` in `ImageAdjustmentTests`, and an unbaked copy in `ProjectCopyTests`.
- Adjustment layers drawn (9.5b): `LayerAdjustment::apply` runs the kind's own filter (Hue/Saturation and Levels through their filters, Curves, Exposure and the Gradient Map through their settings), Grain placed by the region it is given: its origin and its units a pixel, `region.width / image.width`, so the export and `drawLiveComposite` keep the pattern in the document however their drawing is cut or scaled. Known difference, Swift's too: the canvas places layers by scale and centre, not through the painter's transform, so its region is the view's and Grain's pattern follows the view, moving under a pan and differing from the export (`grainFollowsTheViewOnTheCanvas`). `LiveMaskRenderer` gains Swift's three hooks as public members: `adjustment`, `adjustmentOpacity` and `adjustmentClip`, which multiplies the layer's own mask into device coverage where Swift clips the context. `prepareStacks` keeps every layer's mode (Swift's `blendMode`); Swift's `adjustment(base) == nil` there is dead and left out, since nothing clips to an adjustment (`LiveMaskGraph`). `drawComposite` hands an unclipped adjustment to `adjust` and draws a clipped one only inside its base's stack, where `adjust` runs on the group after its unpremultiplied base, as Swift's. `adjust` reads the painter's device (a `QImage`, as `LayerRenderer` requires; else a `logic_error`), converted to the kernels' `RGBA8888_Premultiplied` at a pixel ratio of one, within the pixel budget (past it, a warning on `omaphoto.rendering`, where Swift's `try?` is silent), applies the settings over the region the device shows (its device transform inverted), blends a mode other than normal at full coverage and restores the original alpha (`layer_extract_alpha`, `layer_unpremultiply_opaque`, `LayerRenderer::composite` for the mode, `layer_restore_alpha`), then mixes the result into the original by opacity × mask × outer clip, rounded once, where Swift mixes by opacity (`CIBlendWithMask`) and then draws through the soft clip, and draws it back one to one in `Source` mode under the painter's own clip, as Swift's copy honours the context's clip, the painter's whole device transform cancelled as the stack group cancels it, so an image of any format or pixel ratio takes it (the app hands it only `RGBA8888_Premultiplied` at a ratio of one: the export's image, a stack's group, `AdjustmentSurface`'s surface; a caller of the renderer itself may hand it any image). A failure to allocate is `ExportError`, caught there as a warning; anything else is a bug and is left to crash. `ImageExporter::render`, `drawLiveComposite` and the canvas set the hooks as Swift's three places do; `drawLiveComposite` gains Swift's `onSurface` and, when a document holds an adjustment, draws through `AdjustmentSurface`, so a painter's opacity or clip applies to the composite once. The canvas clips an adjustment by its enabled mask, mid-stroke by the edit's tiles (`maskEdit`, shared with the folders' clip, Swift's `liveMaskEdit`), placed by the layer's transform at the view's scale; its `DisplayState` counts adjustment layers with their settings, since an undo restores settings without moving `brushRevision`. Tests: Swift's `AdjustmentLayerTests` (the curves command test moved there from `ImageAdjustmentTests`, its Swift home), `theLiveCompositeDrawsAsTheExport`, `opacityMixesAndGrainSitsInTheDocument`, `everyKindAdjustsThroughItsSettings` and `aFoldersMaskClipsTheAdjustmentsInside` beside them, `anyImageTargetTakesTheAdjustment` beside them, `anAdjustmentAdjustsWithinItsBudgetAndStack` and `anAdjustmentTakesAnyImageTarget` in `LiveMaskRendererTests`, `adjustmentsShowAsTheExportDoes`, `anAdjustmentsMaskClipsItOnTheCanvas` and `grainFollowsTheViewOnTheCanvas` in `CanvasDisplayTests`.
- Editing adjustment layers in the session (9.5c): `Document/AdjustmentEditing.cpp` twins Swift's file, `AdjustmentEditing+Session.h` its session half; `adjustmentEditingID` (a getter and a setter that resumes file requests and notifies, Swift's `didSet`) and `adjustmentOriginal` (a getter) sit in `EditorSession.h`. `addAdjustment` asks for the new layer's editor last, as Swift's. `beginAdjustmentEditing` takes a completion callback: it hides every layer not beneath the adjustment in hierarchy order (the adjustment itself and all above; the records stay for live masks and folders), renders that snapshot through `ImageExporter::render` in a worker (`QtConcurrent::run` with a watcher per call, as each Swift call is a task of its own; the worker catches `ExportError` alone, since a session's snapshot never fails the store's rules), and on the UI thread opens the kind's editor on a layer of that image at the origin: Levels with its histogram (`countLevelsHistogram`, which `beginLevels` shares), Hue/Saturation with `resolvedHSV`, or the filter panel of `filterKind` (declared in `LayerAdjustment.h`, as Swift's extension) with the four settings; then it keeps the original and opens one `Edit … Adjustment` transaction. The editors' layer has an id of its own, so the canvas never shows their previews, and none renders: `updateLevels`, `updateHueSaturation` and `updateFilter` hand the settings to `previewAdjustmentEditing` first (the edited settings, or the original with Preview off) and notify, since settings the layer refuses still change the editor; the three cancels and commits hand the edit to `finishAdjustmentEditing` first (a filter's after its Gradient Map picker closes, as in Swift). `finishAdjustmentEditing` writes the edited settings on OK and the original on Cancel, closes the three edits and the Hue tools (sample mode, targeting, a targeting drag), ends the transaction, clears the request, resumes file requests, asks for canvas focus and moves `brushRevision`. OK writes the settings out even unchanged, so an Exposure or Hue/Saturation layer made without them gains them in a step, as in Swift. A Gradient Map picker stays open when `finishAdjustmentEditing` is called directly (Swift's tests call it; the app's cancel and commit close the picker first), so `setGradientMapColor` keeps Swift's guards: with no filter open, or another kind, it writes nothing; its `committing` term is dead, since a commit closes the picker before it begins. Left out as dead: Swift's `editedAdjustment` returns nil when its kind's edit is gone, which never happens while `adjustmentOriginal` is set (the two are set and cleared together, and every path that closes an edit reaches `finishAdjustmentEditing` first), so the twin reads the edit through `value()`; the `?? .curves` behind `filterKind`, a checked read; `finishAdjustmentEditing`'s cancellation of previews (none runs for an adjustment's editor, and a histogram lands only on a Levels edit still open) and its `hueSaturationPending = nil` (only a preview sets it). Swift's `.task(id:)` cancels a render whose request changed; the landing's guard (the same request, no editor open) does that work here, and nothing in the app changes the request while a render runs (every writer sits behind `canEditLayers`). A fix beyond Swift: Swift's landing checks the request alone, so a Levels, Hue/Saturation or filter edit begun on other pixels while the render ran (choosing a layer and opening one stay possible, as in Swift) would be replaced or joined by the adjustment's editor; the twin's landing leaves that edit alone, clears the request, resumes file requests and logs a warning on `omaphoto.app`. A render or an editor that fails clears the request and sets `brushError`, as Swift's `catch`. `canEditLayers` and `canStartProjectOperation` read the request; `canUseHistory` does not, as in Swift, so undo stays open while the render runs, and an editor may open for a layer undone meanwhile, whose close writes nothing. Swift's `isGroup != true` there is left out as dead: a folder not beneath the adjustment holds nothing that is, and a live mask's source is never a folder. Equivalent mutants: the start guard's request term (the landing asks again; the start's only spares the render) and its `adjustmentOriginal` term (the original never outlives its kind's edit, which the next terms read). Tests: `AdjustmentEditorTests` (Swift's `sharedEditorsKeepPixelsDynamicAndSupportCancel` for every kind, then what lies beneath, the refusals, a failed render, an edit begun meanwhile, the gates and file requests, the Hue tools, a layer undone meanwhile, the signals), Swift's `newAdjustmentLayersStartFromThePaletteRenderAndEditInThePanel` in `ImageAdjustmentTests`, the request as a gate in `SessionGateTests`; tests that add an adjustment and edit on clear the request, as Swift's `add` does.
- Editing adjustment layers in the window (9.5d): `LayersPanel` twins Swift's `.task(id: adjustmentEditingID)`: on every `changed()` (and when made, as a task runs on appear) it compares the request with the one it last began (`m_adjustmentTask`) and begins a new one; a render already under way for the same request lands nothing, so nothing needs cancelling. The footer's adjustment button is a `QToolButton` whose menu (Swift's `Menu`, `InstantPopup`) lists the six kinds by name and calls `addAdjustment`, resting while `canEditLayers` does not hold. Its glyph and the rows' are `LayerIcons` paths for Swift's SF Symbols; `symbol` names each kind's (circle.lefthalf.filled, slider.horizontal.3, the curve path turned a quarter clockwise as Swift turns it, plusminus.circle, paintpalette, circle.grid.3x3), and `adjustmentThumbnail` draws it 1.2 times the rail's size, centred in the row's 36-point square, as the text glyph is. An adjustment's row shows that glyph, "Adjustment · Double-click to edit", and no link for its mask (Swift's `linkable`); a double click on a control makes it active and asks for its editor (Swift's `renameClickedLayer`), one on the name renames. The Layer menu opens with Swift's New Adjustment Layer submenu (the kinds with an ellipsis, named `new…Adjustment`, resting while `canEditLayers` does not hold) and Edit Adjustment… (the active layer's request, for an adjustment layer alone), then a separator. The Levels sheet's caption says "Underlying pixels · alpha-weighted histogram" for an adjustment's editor, and the filter and Hue/Saturation sheets hide "Limited to the selection" there, as Swift's `adjustmentOriginal` terms. Tests: Swift's `adjustmentEditorsUseMovableNonmodalPanels` for every kind in `FloatingPanelTests`; `AdjustmentPanelTests` (the footer and its request, the rows and their glyphs, the Layer menu, the sheets' words); the Layer menu's count and names in `CompositorMenusTests`.
- Layer effects in the document and the session (9.6a): `Document/LayerEffects.h/.cpp` twin Swift's model: the four effects with Swift's defaults, `LayerEffectKind` by raw value in Swift's order (`allLayerEffectKinds`), `LayerEffectSelection`, `LayerEffects` with its helpers. Swift's file runs to 544 lines, so its session extension is `LayerEffects+Session.cpp` with `LayerEffects+Session.h`, and its renderer arrives with 9.6b. `isValid` keeps Swift's bounds and leaves out the `isFinite` terms the bounds already refuse; `offset` falls away from the light, y down. The manifest's `effects` is Swift's synthesized `Codable`, written by hand in `IO/ProjectStore+Effects.cpp`: every key required but `enabled`, which stays out while absent; the store holds no rule for effects, as Swift's. Swift 1.1 gave the record an `effects` key but its `projectSnapshot` and `installProject` never carried it, so its saves and exports dropped the effects; Swift agrees with the twin since 1.2.0 (`5775dd1`, `6230e41`). The twin's record (`hierarchyRecord`) carries them and `ImageLayer(record, …)` loads them, so they save, load and, with 9.6b, export. Elsewhere they travel as Swift lists them: equality, a duplicate and the brush's two commits keep them; Invert's, the filter's, Levels' and Hue/Saturation's commits, a floating merge, a copy between projects and both resizers leave them out. The session's `effectsEditing`, `effectsEditingOriginal` and `effectSelection` are getters; 9.6d gave the first two setters, which notify on a change, for `ContentView`'s check, and made `dropEffectSelection` public for the canvas's press (the list's arrive with 9.6e). `selectLayer`, `selectLayers` and `selectLayerTarget` drop the chosen effect before any guard, as Swift's, so a refusal still drops it and says so (`dropEffectSelection`); Delete and the trash take a chosen effect first. `setEffects` finishes an opacity drag and makes one step of a valid change; `changeEffects` stays with the panel's layer, a step per change as Swift's; Cancel puts back the panel's effect alone. The colour picker gains Swift's effect target (`openEffectColorPicker`, `previewEffectColor`, `closeColorPicker`'s effect case, titles such as "Color Picker (Stroke Color)"); `ColorPalette.h` declares `LayerEffectKind` opaquely, since `LayerEffects.h` includes it. Left out as dead: the `isGroup` terms of `canEditEffects`, `setEffects` and `canCopyEffect` (a folder never holds pixels, `LayerHierarchy::validate` sees to it, so `asset` says the same), `selectEffect`'s `selectedLayerIDs = [id]` (`setActiveLayerID` sets it, and `selectLayer` cannot refuse behind `canEditLayers`) and its effect picker close (every path that clears `effectsEditing` closes that picker first, `ContentView`'s check since 9.6d included). Swift has no effects tests: `LayerEffectsTests` and `LayerEffectsSessionTests` pin its code, and `ProjectCopyTests` the copy.
- Layer effects drawn (9.6b): `Rendering/LayerEffectsKernel` twins `MetalLayerEffects` as a namespace (the class only holds its device): the shader's passes in float and in its order, bands of 32 lines side by side: the alpha, the spread rows and columns, the ring, the bilinear shift, the blur rows and columns, the inner shadow's coverage and the composition, each byte rounded as the shader's `uchar(x * 255 + 0.5)`. The spread is Swift's CPU `extreme`, a sliding window each index enters and leaves once, whose maxima and minima equal the shader's loops, nothing read past the edges; the blur's weights are computed once, since every pixel of the shader computes the same ones, and each tap is added in the shader's order, the columns tap by tap over whole rows. `LayerEffectsKernelTests` replays the shader's loops as written and compares byte for byte. Metal's 80-million-pixel ceiling guards the GPU's buffers, past which Swift falls back to Core Image; the kernel takes what `render` allows, 100 million. Its buffers are allocated before any worker runs, through one helper, and one that cannot be is `ExportError(render)`; the spread's queues are sized by each pass's bands and line length, so a thin layer asks little. Workers write the result through one pointer taken before they start: `scanLine()` detaches, which races. Swift's CPU renderer (`shadowCoverage`, `innerCoverage`, `ringCoverage`, `coverage`, `strokeCoverage`, `fill`) serves machines without Metal and is dead here, as the brush's dab fallback is (8.1). `LayerEffectsRenderer` is `Document/LayerEffects+Renderer.h/.cpp`, since Swift's file runs past 500 lines: `cached` keeps Swift's cache (the pixels and mask by identity, `QImage::cacheKey` for `===`, the switched-on effects by value, eight at most within 64 MiB of results and their sources, first in first out) under a mutex, since the export's worker and the UI both draw; a failure logs on `omaphoto.rendering` where Swift's `try?` is silent, and the layer then draws bare. `placed`, `margin` and `render` follow Swift's; the mask is multiplied in with `DestinationIn`, smoothly scaled, where CoreGraphics clips to it, and the pixels are copied into the padded grid before the kernel runs. `ImageExporter::render` and `drawLiveComposite` draw a layer's effects image through `placed` with its opacity, blend mode and folder clip, the mask already inside it, as Swift's do; the canvas draws them with 9.6c. Equivalent mutant: `cached`'s validity term (`render` refuses the same effects and the cache's catch returns none; the term only spares the warning).
- Layer effects on the canvas (9.6c): `Rendering/EffectsPreviewCache` twins Swift's class, a `QObject` the session holds as `effectsPreviews`, Swift's `@ObservationIgnored` member. Swift's serial queue is a `QThreadPool` of one thread; a request waits 60 ms on a single-shot timer (precise below two seconds) and then joins the pool; Swift's locked `cancelled` is a shared atomic flag; the result is posted back and lands only while its request is still the layer's, Swift's id check. `Request` holds the asset, so a painted layer flattens on the worker. `matches`, the kept `previous`, `seed`, `rendered`, `prepare` and the shared budget (64 MiB of output, 32 to 1536 a side) follow Swift's. A reduced preview scales each source through `QImage::scaled`'s smooth filter, which measures each axis on its own (an area average where it shrinks, bilinear where it grows), for CoreGraphics' high-quality reduction, since a mask may differ in size and shape from its layer; a mask travels as alpha, so its values pass exactly; a render that fails logs on `omaphoto.rendering` and lands none, as Swift's `try?`. The destructor drops the queued renders; the pool's own destructor waits for the one under way. The canvas's completion repaints the view through a `QPointer`, Swift's `[weak self]`. A fix beyond Swift: Swift scales the stroke and the drop shadow for a reduced preview but not the inner shadow, which then shows too wide on any layer past 1536 pixels; the twin scales its distance and blur too.
- `Rendering/LayerEffectsSurface` twins Swift's class: `make` for its failable `init` (80 million pixels at most, a warning past it or on a failed allocation), `matches`, `update` (tiles taken by origin and `cacheKey`, Swift's `ObjectIdentifier`), `compose` and `window`. Swift's CPU fallback (`fill` and the renderer's coverages) serves machines without Metal and is dead here, as the renderer's is; a pass paints on a copy of the surface and publishes it only once whole, so a window, kernel or copy that cannot be allocated logs and leaves the last image, and a pass's tiles count as taken only once redone, so the next update tries them again (a fix beyond Swift, which marks them first and after a failed first pass would show the empty context). The window draws a painted base from its tiles, the tiles over it, then multiplies the mask into the layer's own pixels once (`DestinationIn`, smoothly scaled); Swift draws the base and the tiles through the soft clip each, so a half-covered pixel keeps a quarter of the old pixels under the paint (known difference). Fixes beyond Swift: Swift widens a change by the margin, the room outside the layer, and reads a reach round that which leaves out the inner shadow, so an inside stroke or an inner shadow stays stale past the margin and the inner shadow is cut at the window's edge (dark bands while painting). The twin widens and reads by the reach, the inner shadow's included, and stops every window at the surface's bounds, where the renderer's padding ends: a first pass equals `LayerEffectsRenderer::render` byte for byte, and every later pass a fresh render of the painted pixels (`LayerEffectsSurfaceTests`). Left out as dead: the reach's `isEnabled` terms (the surface is made from the shown effects), Swift's empty-region guard and its zero-size terms (a stroke's grid is a pixel at least, and a change lies inside it), and the reach's `ceil` and the region's `integral` (every box is made whole where it is used, and tiles lie on whole pixels).
- The canvas's effects (9.6c): `DisplayState::Layer` carries `effects`, `drawLayers` calls `prepare`, and `synchronizeDisplay` hands a finished stroke's surface to the cache as a seed first (`handOnStrokeSurface`, Swift's opening lines). `drawOwn` keeps Swift's order: the warp, the distorted effects, the distortion's preview, the effects preview, then the stroke, the shape's preview and the colour edits' previews, so a layer with effects shows its effects over its own pixels while Levels, Hue/Saturation or a filter previews it, as Swift's does (`EffectsCanvasTests` pins it). A fix beyond Swift: Swift asks the cache twice a draw, first with the mask unplaced and the stored transform, then with what the layer shows; the first request wins, so a placed mask clips the preview unplaced, and while a transform edit moves such a layer the two requests cancel each other and render without end. The twin asks once, with the shown mask and transform, before the distortion's branches, so the mask is worked out first. The drawing functions lost their `const`: they update the stroke surface and hand the cache a repaint. `drawStroke` moved to `EditorCanvas+Effects.cpp` beside `strokeSurface` and `handOnStrokeSurface`, keeping `EditorCanvas.cpp` under 500 lines. `Distort.cpp` gains `DistortEffectsCache`, both `distortedEffects` (`const` with a mutable cache, as `distortPreview`; a warp that throws leaves the effects off, Swift's `try?`) and `commitDistort`'s seed, the cache cleared after the step as Swift's `defer` clears it. Swift has no tests for any of this: `EffectsPreviewCacheTests`, `LayerEffectsSurfaceTests` and `EffectsCanvasTests` pin its code. Equivalent mutants: the pool's thread count (a result lands by its request's id, whatever the order), the destructor's `clear` and every cancelling of a superseded request, the worker's two checks included (the landing's id check drops them; they only spare renders), the matching's `&&` between two absent masks (the sources must match anyway), `!previous` before the seed (a landed result clears its seed), the resizes skipped at full size (a draw at 1:1 copies); in the surface, the reach's floor of one (an overlay reads each pixel alone) and the stroke's `+ 2` (the spread reads `lround(size)`), `inner`'s cut at the bounds (QPainter clips the draw alike), the first region's margin (the reach goes as far) and the window's skip of tiles off its region (it only spares draws); `commitDistort`'s clearing of its cache (keyed by its inputs, the cache only frees memory). `EffectsFailureTests` starves a stroke's first pass through `AddressSpaceLimit`, in a binary of its own: the canvas logs it and shows the last effects. Untested failure paths: `rendered`'s and the landing's tests of a result, and the resize's null check, differ only when a preview fails, and a preview asks too little for `AddressSpaceLimit` to reach a worker's arena.
- Layer effects' panel (9.6d): `UI/EffectsSheet.h/.cpp` twin Swift's sheet: 340 points wide with 20 of padding and 16 between rows, the kind's headline (13 pixels, semibold), the stroke's Position as two touching checkable `QToolButton`s in an exclusive `QButtonGroup` (Swift's segmented picker; its hidden label is the box's accessible name), the colour as the Type bar's `SwatchButton` (36 by 18, radius 3, a half-black rim, `<Kind> color` its tooltip and accessible name, black while the effect is missing) opening `openEffectColorPicker`, Swift's `slider` rows (a 64-point title as the slider's buddy, a 130-point slider over a thousand steps of its range that sets the value unrounded, as Swift's continuous binding, a 48-point right-aligned `PickerField` with the title as its accessible name and placeholder, its unit two points after), then Cancel and OK ten points apart, OK the default button and Cancel no auto-default, so Return anywhere means OK, as Swift's `.defaultAction`. A field shows its value whole, ties to even as Swift's `.number` format rounds; it applies a readable finite number on leaving or on Return (which then goes on to OK), clamped to the slider's range as Swift's binding, reverts other text, keeps its typing while other changes arrive, and steps with Up and Down (Shift ten) from the session's value, clamped, the step replacing any typing and showing, as the picker's entries do; a change through the row's own slider (a wheel leaves the keys with the field) replaces it too. Each change is a step, as Swift's `changeEffects`. On every change of the picker's colour the sheet calls `previewEffectColor` (Swift's `onChange`), and it repaints its swatch on every change. While the layer lacks the effect the controls hide, as Swift's `if let effect`. `ContentView::synchronizePanels` first runs Swift's layers check (an edited effect gone from its layer, or the layer gone, closes an effect picker without its colour and clears `effectsEditing` and `effectsEditingOriginal`; a palette's picker stays), then shows the sheet in `effectsPanel`, titled by the kind, whenever `effectsEditing` changes (a new choice, a new sheet), its close button and Escape cancelling, and closes it when the choice clears. The footer's effects button (`sparkles` in `LayerIcons`: three four-pointed stars) is an instant-popup menu of the four kinds, each with an ellipsis, resting while `canEditEffects` does not hold. While an effect is chosen (`selectedEffect`, so a choice an undo took away names the layer again) the trash says `Delete selected effect` and the Layer menu's Delete `Delete <Kind>`. The canvas's left press lets go of a chosen effect before any guard, Swift's first line of `mouseDown`; other buttons keep it. Swift has no tests for the window's effects: `EffectsPanelTests` pins them, and `LayerEffectsSessionTests` the new writers' signals. Equivalent mutants: the fields' `OmitGroupSeparator` (no range reaches a thousand) and OK's explicit `setDefault` (a dialog makes its first auto-default button the default as it shows, and Cancel is none).
- Effects in the list (9.6e): `LayerEffectRow` (declared in `NativeLayerList.h`, its code in `NativeLayerList+Effects.cpp`) twins Swift's private class: a 24-point row under its layer for each effect, in Swift's order, the cell 52 points tall and 24 more for each (`rowHeight`, `effectHeight`). The list activates its column's layout after configuring the cells, as `noteHeightOfRows` changes heights at once, so no press lands on a row that a taller one still covers. The eye (20 by 22, 38 points in plus the layer's step, flat, `eye` or `eye.slash` in `PlaceholderText`, named `Hide <Kind>` or `Show <Kind>`) toggles the effect in one step and rests while `canEditLayers` does not hold; the name (11 pixels, `WindowText`, `PlaceholderText` while hidden) ends in an ellipsis when narrow, as `.byTruncatingTail`; the row's tooltip is Swift's with Alt for Option, its accessible name `<Kind> effect`, and an accessible interface of Swift's group role chooses the effect on the press action (`accessibilityPerformPress`). The rows are made anew only when the kinds change, else reconfigured in place; the old ones are hidden and deleted later, because a row's own double click may cancel a new effect's panel on the same layer, whose Cancel removes that effect and rebuilds the rows under the press, where Swift's reference counting keeps the row alive. A chosen effect's row shows `Highlight` at 30%, and while one is chosen the cell's selection hides, as Swift's table selection does. Presses follow Swift's `mouseDown` order: Alt without Ctrl on the strip (the bottom 10 points of the taller row, over its last effect; Swift's `min(10, height / 3)` is dead, rows being at least 52) clips through `clickRow`; on an effect, Alt without Ctrl arms a copy while layers can be edited, the release choosing the effect and a move past `startDragDistance` with Alt still held starting a `QDrag` of `UUID:Kind` under `effectType` with the list's token, offering Copy alone under the duplicate cursor, as the row's Alt drag does; any other left press chooses the effect, a double click editing it (Swift's `clickCount > 1`); the eye's Alt presses are the row's, ignored in its filter so they go on to it (Swift's `hitTest`). An effect dropped from the same list (Swift compares the source's session) lands on the row under the pointer, filled, as a copy, where `canCopyEffect` allows. A left press below every row lets go of the chosen effect and, without Ctrl or Shift, of every layer, as Swift's table with `allowsEmptySelection` does (a gap the list of 4.6 left). Known difference: the two points between rows take no press, where Swift's rows take their spacing. Swift has no tests for the list's effects: `LayerEffectRowTests` pins them, with `QDrag::exec` defined in its binary as in `LayerDragGestureTests`.
- Remove Background (9.7): Apple's Vision has no Linux twin, so `Document/SubjectRemoval` runs U²-Net (Qin et al., Apache-2.0, its text in `licenses/U-2-Net.txt`) on ONNX Runtime (MIT), as rembg converted it (MIT): `u2net.onnx`, 175,997,641 bytes, SHA-256 `8d10d2f3bb75ae3b6d527c77944fc5e7dcd94b29809d47a739a7a728a912b491`, the MD5 rembg pins. Chosen over `u2netp` (poorer edges), `silueta` (no clear source) and IS-Net's `isnet-general-use` (sharper, but the DIS repository puts only its code and metric under Apache-2.0 and its DIS5K training set under terms of its own, so the weights' terms are unclear); 90 ms a mask on 32 cores, measured. The model is found with `QStandardPaths::locate(GenericDataLocation, "omaphoto/u2net.onnx")`, so a package installs it as `share/omaphoto/u2net.onnx` and the dev image carries it in `/usr/local/share`. `Dockerfile.dev` fetches it and Microsoft's ONNX Runtime 1.21.0 build (Ubuntu 24.04 packages none; Ubuntu 25.04 on and Arch ship theirs with the same CMake config), both by pinned checksum; that build's CMake config goes to `/usr/local/lib/cmake`, which Ubuntu's CMake searches, and its library to `lib64`, where the config looks for it; CMake links `onnxruntime::onnxruntime`. One `Ort::Session` serves the process, loaded on first use; a load that throws leaves it unloaded, so the next use tries again. Every model step passes through `vision`, where ONNX Runtime's exceptions become `SubjectRemovalError(model)` and a failed allocation (the input buffer, the runtime wrapper's own vectors) becomes `ExportError(render)`, so none passes a worker's catch. `SubjectRemovalError` twins `SubjectRemoval.Failure`: `noSubject` with Swift's words, and a `model` kind for a missing model (naming every folder looked in) or ONNX Runtime's own message, where Swift passes on Vision's error. The input is the paper's and rembg's: the image premultiplied (clear reads as black), scaled to 320 by 320, divided by its brightest byte, then ImageNet's mean and spread; the first output is stretched from its lowest to its highest value, truncated to bytes as rembg does, and scaled to the layer's grid. An output with no value at or above one half is Swift's `noSubject` (flat images give under 0.03, measured). Known difference: U²-Net's mask is made at 320 points, so Basic's edges are softer than Vision's; Advanced's Refine pulls them onto the layer's own. The raw mask of the last image is kept by `cacheKey`, Swift's `MaskCache`. `Document/GuidedMatte` twins Swift's file: `box` keeps Swift's float sums, the column pass running a row at a time; `filter` frees what it no longer needs; `levels` scales through premultiplied RGBA (Qt's smooth scaling of Grayscale8 strays by a level shrinking and up to ten enlarging, probed) and reads gray over black through `qGray`; `refine` draws back up with `SmoothTransformation`, and the model's mask is enlarged through premultiplied RGBA too. `refined` does Core Image's Shift Edge (a Gaussian with the edge repeated through `PixelAdjust::gaussianBlur`, then Swift's clamp-and-scale cut) and Contrast in float over bytes, rounded once; the blur rounds to bytes first, a level at most. Contrast runs unconditionally, being the identity at 0. The preview (`run`) refines a copy 1400 long at most and multiplies each premultiplied byte by the mask into pixels of its own, copied before the loop so a copy that finds no memory is `ExportError(render)` (a shared image would copy inside the loop and come back null); the commit (`subjectMask`) refines at full size, multiplies in a mask of the layer's own grid (another grid is a `logic_error`, never read past) (disabled or not, which is then shown, as Swift's), blends through a selection over that mask or over white, and writes the mask in one `Remove Background` step with the mask chosen; its worker flattens painted pixels and masks. A fix beyond Swift: a placed mask's pixels were dropped but its placement kept, so the new mask, made in the layer's grid, sat at the old placement; the twin clears the placement. The filter sheet shows Swift's words, Quality as two touching checkable buttons (the label hidden, its accessible name) and Advanced's Refine, Contrast and Shift Edge rows with Swift's help, made once and shown while Advanced is chosen, as Swift's `if`. Equivalent mutants: the cache's key (only the time differs) and the commit worker's catch of `SubjectRemovalError` (after its preview succeeded, only ONNX Runtime failing mid-run could throw there). Tests: `GuidedMatteTests` (the box against plain sums, the filter against He's steps in doubles, overshoot included), `SubjectRemovalTests` (Swift's `visionRequestRunsOnAnImage` among them, on a red disc the model finds), `SubjectRemovalModelTests` (a binary of its own: a broken model, a missing one, then the real one), `SubjectRemovalFailureTests` (a starved preview and a starved model input, under `AddressSpaceLimit`, glibc's mmap threshold fixed so large requests map memory the limit counts), `RemoveBackgroundTests`, the sheet in `FilterControlsTests`, the kind in `FilterModelTests` and both menu tests.
- Crop (10.1): `Document/Crop.h/.cpp` twin Swift's file, `Crop+Session.h` its session half. `CropGeometry` is a namespace; `CropDrag::Mode` is a kind and an index, as `TransformDrag::Mode` twins an enum with payloads; `CropSnap`'s `nearest` and Swift's local `shift` are file helpers; `cropSnapTargets` returns `SnapGuides`, Swift's tuple. `valid` and `commitCrop` read the frame normalised, as `CGRect`'s `width` and `minX` read it standardised; `valid`'s `isFinite` terms are left out, since the ranges refuse NaN and infinities. `cropRect`, `cropRatioChoice` and `cropError` are getters and setters that notify on a change. `commitCrop` takes a completion callback, posted on every path; the snapshot is taken and the worker started before anything changes, the resize runs through `QtConcurrent::run` and a `QFutureWatcher` with the project busy, the worker catching `ProjectError` and `ExportError` (`CanvasResizer::resize` turns a `std::bad_alloc` of its records and maps into `ExportError(render)`, as 9.7's `vision` does), and the result is moved out (`takeResult`) and installed through `applyDocumentSize`, one `Crop` step; memory that runs out while the snapshot is taken or the result lands sets `cropError` to the render error and changes nothing else, so the project is never left busy. Only a crop that landed drops its frame (Swift drops it first); a failure sets `cropError` to the error's text and keeps it, and the project is freed after either, Swift's `defer`. Hooks: `selectTool` cancels on a change of tool and opens the Crop tool on the whole canvas, Free, when no frame is drawn; `restore`, `beginTransform`, `importImages`, `beginLevels`, `beginFilter` and `ProjectController::begin` cancel; `installProject` and `clearProject` drop the frame and announce it with their own signal; `canEditLayers` reads `cropRect`, `canUseHistory` does not, as in Swift. The canvas's gestures live in `EditorCanvas+Crop.cpp`. A press on a grip resizes (the first region holding the point, corners first, Swift's `first(where:)`), one inside a drawn frame that is not the whole canvas moves it, any other drops the frame and draws anew; `CGRect.contains` leaves out the far edges, so the file's own `contains` does too, where `QRectF::contains` takes them. The snap is built at the press, 8 view points (`cropSnapDistance`); Alt keeps the middle still, Ctrl leaves the edges unsnapped (Swift's Control, as the Move tool's snapping reads it), and either key changing mid-drag reshapes the frame at the last hover point, as Swift's monitor reads the mouse. Swift's `?? CGRect(origin: pixel, size: .zero)` and its `if let cropSnap` are dead (the Crop tool always shows a frame; the snap is built with the drag) and are checked reads. A drag goes on under the left button alone, with the Crop tool, a free project and a document, as Swift's `mouseDragged`; a move without the left button ends it, since Qt can lose a release. `endCropDrag` is Swift's `cropDrag = nil` with its `didSet`: the release, a lost focus, Escape (cancel) and Return or Enter (commit) end the drag and free its cursor. Wheels and pinches rest mid-drag. The drag keeps the cursor its press showed in `m_dragCursor` (Swift's `.current`, with the cursor rects disabled), taken before a new frame drops the old one. Cursors: picking first, then the open hand under Space, then over a grip Qt's resize shape for Swift's frame position (top left and bottom right `SizeFDiagCursor`, top right and bottom left `SizeBDiagCursor`, top and bottom `SizeVerCursor`, left and right `SizeHorCursor`; Qt's shapes say no inward or outward), elsewhere the crosshair. `TransformOverlay` gains `cropViewRect`, `cropResizeRegions` (a `CropRegion` struct for Swift's tuple) and `drawCrop`: the canvas outside the frame under 60% black (a `QPainterPath`'s own odd-even rule), a white frame, the thirds at 40% white in one path so their crossings paint once, and 8-point white grips with black rims, antialiased, with CoreGraphics' butt caps and miter joins. Known difference: at 1× QPainter strokes one-point lines through its cosmetic stroker, which draws no joins, so the outer corner pixels of the frame and the grips stay partly clear, as the text box's (8.9c). The dimming spans the canvas, so a frame that appears or goes repaints the canvas; a frame that changes repaints the old and the new frame with their grips (`drawnRect`), since outside both the dimming stays. That is the twin's `cropDraggingRedrawsOnlyTheOverlay`: Qt has no layers, so the union of the frames repaints, pixels included, never the canvas. Under the Crop tool `renderBounds` takes the frame's union, so a frame past the canvas shows the checkerboard it would take in and redraws the canvas, as in Swift. `CropControls` is the tool's `ToolHeaderBar`: its row spaced 14 as Swift's `HStack`, Swift's labelled picker a "Ratio" `QLabel` (its combo box's buddy) and a `QComboBox` sharing 170 points, a choice that changes the ratio calling `changeCropRatio` (Swift's `onChange`), the frame's size as whole pixels (Swift's `Int`, truncated) grouped through the English locale like the status bar (`monospacedDigit` has no Qt 6.4 twin), and Cancel and Apply Crop resting without a frame; the bar rests while busy shows or without a document. `ContentView` shows it for the Crop tool and the "Couldn’t crop" alert over `cropError`. Left out as dead: `renderBounds`' tool test (a frame lives under the Crop tool alone: every other way to another tool cancels it or asks `canEditLayers`, which a frame refuses) and the strips' `max(0, …)` in `cropResizeRegions` (a strip it would clip lies under the corners' regions, which take the point first). Equivalent mutants: `contains` on the visible frame for the drawn one (while a frame is drawn they are one), the tolerance's `max(…, 0.0001)` (the zoom's floor keeps points per pixel above it), `cropMove`'s answer after a lost release and after a step (the rest of the move only refreshes the cursor), the strips' ends (under the corners), the frame's caps and joins (its corners lie under the grips) `drawCrop`'s `setBrush(Qt::NoBrush)` (the painter arrives with none) and `takeResult` for `result()` in the landing (a copy asks only more memory, and its failure is caught the same). Tests: `CropTests` (Swift's six session and geometry tests; symmetric drags, snapping by side, bounds, ratios), `CropSessionTests` (a failed crop, refusals and the busy project, the signals, every hook, a flipped frame, one step that ends redo), `CropFixtures.h` (`committed`), `CropCanvasTests` (Swift's `cropDraggingRedrawsOnlyTheOverlay`; drags, Alt and Ctrl mid-drag, keys and lost releases, cursors, the dimming, a frame past the canvas), `CropControlsTests`, `CropFailureTests` (a binary of its own whose `main` shares the main heap among threads, `M_ARENA_MAX` 1 before any thread starts, and maps large asks, so a worker's allocations meet `AddressSpaceLimit`: a worker in an arena of its own grows its reserved heap past the limit; the snapshot, the worker and the landing each run out in turn), the bar and the alert in `ContentViewTests`.
- Canvas and image size (10.2): `flipCanvas` sits in `LayerFlip.cpp`, as Swift's extension: after `commitTransform` and `cancelCrop` it asks `canEditLayers`, mirrors every layer's transform and every placed mask across the canvas's middle and the selection's outline through a `QTransform` (the path keeps its fill rule), one `Flip Canvas Horizontal` or `Flip Canvas Vertical` step; Swift's `finishOpacityEdit` is left out, since `commitTransform` has run it. `UI/CanvasSizeSheet` is Swift's form in a 450-point column: the title at 17 pixels, bold, the current size grouped through the English locale, the memory as Foundation's `ByteCountFormatter` counts it for memory (binary units: bytes, whole KB, MB to one place, GB to two, trailing zeros dropped; `UI/ByteCounts` since 10.3), a `Mid` divider, Units as a labelled `QComboBox`, Width and Height as `PickerField`s (a readable number applies on Return or on leaving, other text goes back, Swift's value binding; printed as Swift's `.number` to three places, none trailing, never grouped, as every field of the twin, halves rounding to even as Foundation's formatter rounds them), the Relative and Lock toggles (locking takes the width's proportions at once, Swift's `onChange`), the New line or the invalid note in `BrightText`, the anchor grid (nine 25-point buttons in an exclusive `QButtonGroup`, each a circle filled in the accent when chosen for Swift's `circle` and `circle.fill`, with Swift's help as the tooltip and accessible name and "Selected" as the accessible description, Swift's accessibility value), the anchor's name and note, the Canvas extension picker, and for Custom Swift's `ColorPicker` as a label and a 36 by 18 `SwatchButton` that opens a `QColorDialog` without alpha, the desktop's colour dialog where SwiftUI opens the system panel; then Cancel and the default OK, which rests while the draft is invalid, so Swift's guard in its action is left out. Units, Relative and Lock change only through their own controls, so nothing writes them back, and so does the image sheet's Resample. A wheel over Units changes the unit without the focus, so both sheets take the focus to Units first: a size still being typed commits in the unit it meant. `UI/ImageSizeSheet` is Swift's sheet: Pixels and Percent only while resampling, Width and Height converting by unit (Swift's binding refuses a number that is not positive; without resampling a size sets the resolution), Lock, disabled without resampling, the resolution with its unit (in inches or centimetres a new resolution scales the pixels, Swift's `onChange`), Resample (turned off, the pixels go back, the lock closes and Pixels or Percent becomes Inches), Sampling while resampling, the explanation, the result or the invalid note, Cancel and the default Resize. The controller's `canvasSize` and `imageSize` live in `IO/ProjectController+Resize.cpp` (with 10.3's exports the controller's file would pass 500 lines) and take a completion callback: refused without a window, a document or `begin`, as Swift's guards; the sheet is a window-modal `QDialog` over the window (`sheet`, Swift's `beginSheet`), whose Escape and close button cancel; the project stays busy until the sheet answers and the resize lands, or its alert is dismissed, Swift's `defer`. `resizeProject` takes the snapshot and starts the worker before anything changes, the worker catching `std::runtime_error` (both of the resizers' errors), and moves the result out and lands it through `applyDocumentSize` or `applyImageSize` (staged since 10.1); memory that runs out while the snapshot is taken or the result lands is explained as the render error. The alert opens from the handler, once the unwinding has freed what failed. The IO file includes the sheets, as Swift's controller hosts them. The Image menu gains Canvas Size… (Ctrl+Alt+C) and Image Size… (Ctrl+Alt+I), enabled with a document while the controller can start, and Flip Canvas Horizontal and Vertical, enabled by `canEditLayers`. Tests: `CanvasSizeSheetTests`, `ImageSizeSheetTests`, `ProjectResizeTests` (the sheets over a window, typed and answered by keys, a cancel, a refusal, a failure's alert), `ProjectResizeFailureTests` (a binary of its own, `main` as `CropFailureTests`': the image resizer, the snapshot, the worker and the landing each run out), the canvas flips in `LayerFlipTests`, the entries in `CompositorMenusTests`.
- Exports (10.3): `IO/ProjectController+Export.cpp` holds `exportPNG` and `exportJPEG`, each with a completion callback. `exportPNG` asks for a document and `begin` (no window: its panel then stands alone), takes the snapshot, opens the panel and renders, encodes and writes in one worker (`exportWork`, which catches `std::runtime_error`, the exporter's errors and the write's); `exportJPEG` also needs the window, renders in a worker (catching `ExportError`), shows `JPEGExportSheet` in the window-modal `sheet` of 10.2, then the panel, then writes the sheet's bytes in a worker. The project stays busy until the file is written, the flow is cancelled or its alert is dismissed, Swift's `defer`; a snapshot that finds no memory is explained as the render error, and `ImageExporter::render` and `jpeg` turn `std::bad_alloc` into `ExportError(render)` at their doors (function-try-blocks), which also serves 9.5c's editor render; the PNG snapshot's copy for the worker and `exportWork`'s launch are guarded too, explained as the render error. The launch's guard is not reached by the tests: its few small allocations fail only under a limit that fails the alert as well. The panel's callback and `showError`'s are moved, never copied, since the PNG flow's completion holds the snapshot. `exportPanel` is Swift's `NSSavePanel` for one type: a `QFileDialog` titled Export PNG or Export JPEG with the type's name filter and default suffix, suggesting the project's name (`ProjectTab::nameWithoutSuffix`, Swift's `deletingPathExtension`) or Untitled with `.png` or `.jpg`; a chosen name without one of the type's suffixes (`png`; `jpeg`, `jpg`, `jpe`; any case) gains the preferred one (`png`, and `jpeg`, `UTType.jpeg`'s preferred extension), where the Mac panel enforces the type, and as with Save As a completed name where anything exists is refused with an alert. `ImageExporter::jpeg` takes Swift's three cancellation points as an optional `cancelled` test, throwing `CancellationError` (Swift's type) before the flatten, before the encoding and before the preview. `UI/JPEGExportSheet` twins Swift's sheet: the title, the 560 by 330 preview on gray 0.12 (the encoded preview fitted, centred and smooth; while updating, a 64-point plate of the window colour at 85%, Swift's regular material, behind a 32-point busy `QProgressBar`), Quality as a slider in hundredths with its percent (`lround`, Swift's `rounded()`) 45 points wide and right-aligned, the matte as a label and a 36 by 18 `SwatchButton` that opens a `QColorDialog` without alpha (the same colour asks nothing, as Swift's `onChange`), the raster's size grouped with "px · sRGB", then the error in `BrightText`, or the file's size and "· encoded preview, fitted to window", or "Updating preview…", and Cancel and the default Export…, enabled only while a ready result stands. Swift's `.task(id: options)` is `request`: it sets the last request's flag, clears the error and restarts `jpegWait`, a 200 ms single-shot `PreciseTimer` (Swift's sleep), whose timeout encodes in a worker holding the new flag; a result or error lands only while its flag is clear, Swift's check after the await; the destructor sets the last flag, as SwiftUI cancels the task with its view. Export stores the quality under Swift's key in `QSettings`; a stored value counts when it reads as a finite number, clamped to 0–1. `UI/ByteCounts` is Linux-only: Foundation's `ByteCountFormatter` in its memory style (binary) and file style (decimal), shared by the canvas sheet and the JPEG sheet: bytes grouped, KB whole, MB to one place, GB to two, trailing zeros dropped. The File menu gains Export PNG… (Ctrl+Shift+E) and Export JPEG… (Ctrl+Alt+Shift+S) after Save As, enabled with a document while the controller can start. Copy Merged came with 7.4. Tests: `JPEGExportSheetTests`, `ProjectExportTests` (the real panels and alerts from `DialogDesk`, names typed in full since a panel opens where the last one went, and the File menu's entries), `ProjectExportFailureTests` (a binary of its own: the render's door, the snapshot, the JPEG worker; `DialogDesk::aroundAccept` sets a limit around a panel's accept alone, since a dialog that paints under one can fail in FreeType and abort; the panel limits sit at 2,560 KB, above the snapshot's peak of 2,300 KB (768 KB and a 1,532 KB mapping, reached before the panel allocates) and one arena growth, below a copying mutant's 3,060 KB peak, measured in 12.8d, because the heap's free chunks count on top of a limit and shift with load; `limited`'s `malloc_trim(0)` is an equivalent mutant, since no free top chunk serves a 1,532 KB mapping), `ByteCountsTests`, the cancellation points in `JPEGExportTests`, the shortcuts and the count in `CompositorMenusTests`. Equivalent mutants: the options a result lands with taken as the current ones (only the newest request lands, and its options are current), the `!m_error` terms of the size's visibility and of Export (an error follows only a failed encoding of options that never became ready, and encoding is deterministic), and the destructor's flag (it only stops a worker whose result nobody reads).
- File and picture drops (10.4): `IO/ImageFileDrop` twins Swift's enum as a namespace. `importProviders` takes the drop's `QMimeData`, where Swift takes item providers: each local file URL is a file, in order; a URL that is no file counts as unreadable, unless no file came at all and the drop holds a picture (a browser's or a screenshot's), whose bytes are copied to `Dropped-<UUID>` in the temporary folder, as Swift's `temporaryFile` copies a promised file, the format chosen in Swift's order (PNG, JPEG, HEIC, TIFF, then any `image/` type) and the suffix from Qt's MIME database. The files go to the workspace's `receive` or, without a workspace, to the session's `importImages`; once that has run, a drop with anything unreadable adds Swift's words to the session's import error, after the importer's own ("from the file manager" where Swift says "from Finder"). Swift's `projects:` parameter has no caller and is left out. `holdsImages` is Swift's drop types but the layer row's: a local file or a picture. `receiveProviders` copies layer rows as before and hands anything else to `importProviders` one provider at a time (`providers`: a URL each, or, when no file came, one item holding the preferred picture alone, so a lazy drag is asked for nothing else, as Swift asks for one format; its web addresses are left behind, since alone they read as unreadable either way), each after the last has run, for the tab then in front, whose session hears what could not be read and stays alive until its import has run; so an import error holds the next file until it is dismissed, Swift's gate between providers. A copied picture that cannot be written whole (its flush checked, since `QFile` buffers) is removed and counts as unreadable; a failed flush fails `QFile::remove` too, so the copy is closed and unlinked by path. An open alert shows its message as it stands (`showAlert` updates it), as SwiftUI's alert re-reads it. The canvas, the tab buttons and the New canvas button take files and pictures as they take rows (a canvas without a workspace under Swift's session guards, Levels, busy, the new-canvas sheet, the importer and a rename, importing into its own session); Alt refuses only a row, as Swift's `validateDrop`. Tests: `ImageFileDropTests`.
- Slider snapping (10.5): `UI/SliderSnap` twins Swift's enum as a namespace. Swift swaps `NSSliderCell.startTracking` so that a press on the track sets the value whose knob is centred there before tracking begins; the twin's `install` puts one application event filter in place, once, as Swift's lazy static swaps once: a left press on an enabled horizontal `QSlider` with a range, outside its knob and with travel for it, sets the slider down, then sets the value under the press (`QStyle::sliderValueFromPosition` over the groove less the knob, the knob's half-width off, flipped for an inverted slider), and presses where the knob now is, the original press consumed, so Qt drags the knob from there even when the slider's owner rounds the value and moves it (a filter's field); a press made with another button held is left to Qt, which refuses it. So editing begins before the value, Swift's order (the opacity slider's drag opens its one step first), and a press on the knob drags it from where it is. QSlider keeps its style option protected, so the filter builds one as `initStyleOption` does. Qt's own absolute set (`SH_Slider_AbsoluteSetButtons`) would set the value before the press and recentre a pressed knob, so it is not used, but it is the test's oracle for where the knob lands. `main` installs it after the theme. Tests: `SliderSnapTests` (Swift's `clickingTheTrackSnapsTheKnobAndStillEditsTheValue`: the value under the press at once, editing begun first, a drag going on, the release; the knob, other buttons, a disabled, vertical, empty, inverted and narrow slider). Equivalent mutant: the groove's own offset, zero under Fusion, the app's one style. The call in `main` is not under test, as the theme's construction there is not.
- Selection modifiers, Select Subject, Soft Light and the font menu (12.1, Swift 1.1.1–1.1.4): `DocumentSelection` gains `feather`, the fade's reach in document pixels. Its coverage is filled antialiased and blurred by `PixelAdjust::gaussianBlur` at sigma feather / 2 with the edge repeated, Core Image's `clampedToExtent`; `coverageBounds` grows the outline's box by `ceil(2 × feather)`, and the clip, the copy region and a mask made from the selection (now drawn through `PixelAdjust::coverage` from the clip) take it. A feather stacks as blurs do (the root of the squares, 250 at most) and travels through moves, Expand, Contract and Inverse. The Select menu's Expand…, Contract… and Feather… ask for an amount (`promptSelectionAmount`); `selectionAmountOperation` is a getter and a setter that resumes file requests, read first by `canEditLayers`, `canUseHistory` and `canStartProjectOperation`. `SelectionAmountSheet` (in `LassoControls`, Swift's file) is Swift's sheet in a `FloatingPanel` named `selectionAmountPanel`, titled by the operation; its note keeps its room while hidden, as SwiftUI's opacity; `QString::toInt` trims spaces as Swift's `trimmingCharacters` does. The selection bar gains Feather and its amount (1–250). Select ▸ Subject (Ctrl+Alt+A) draws the live composite, runs `SubjectRemoval::subjectMask` in a worker with the project busy (a completion callback, as the other jobs), and on the same document applies `MaskTracing::whitePixels` (at least half gray) as the selection, one `Select Subject` step, or sets `brushError`; `canSelectSubject` leaves out Swift's document and busy terms, which `canEditLayers` reads. Soft Light joins `LayerBlendMode` after Overlay as QPainter's `CompositionMode_SoftLight`, which follows the PDF formula `BlendModeTests` holds. `TypeFontPicker` is Swift's: the style's own name alone until the menu opens, a missing name added at the end, an open menu left alone, the face already shown writing nothing, the current name elided at its end within 210 points (Fusion's label draws a pixel in from each side of the edit field). Point text caches its measure by style in the inline editor, and `setTextDraft` resumes file requests only when a draft ends, as Swift 1.1.3's. Swift's `Geometry` cache, which skips AppKit's frame work, has no twin: the canvas draws the editor. Equivalent mutants: the editor's box branch (`textBoxSize` returns the box), `setTextDraft`'s ended test (`resumeFileRequests` asks `canStartProjectOperation`, which a draft refuses). Tests: `SelectionFeatherTests` (Swift's, then stacking, travel, bounds and the sheet's session half), `SelectionAmountSheetTests`, `SelectSubjectTests`, `TypeFontPickerTests`, and the menus, blend modes and Type bar in their files.
- Folders, opacity and Snap (12.2a, Swift 1.1.5–1.1.6): a folder takes an opacity that multiplies into each layer inside it, never composited as a unit, since folders pass through. `LayerOpacity::effective` (in `LayerGroups.h`) walks up to 64 folders, a lookup standing for Swift's closure; `ImageLayer::effectiveOpacity`, `ProjectLayerRecord::effectiveOpacity` (declared in `ProjectStore.h`, defined in `LayerGroups.cpp`, as Swift's extension) and `CanvasDocument::effectiveOpacities` twin Swift's, the last refusing a repeated id with a `logic_error` where Swift's dictionary traps. Every drawing path takes it: the export, `drawLiveComposite`, the canvas (its every draw, adjustments included, and `DisplayState`, so a folder's change redraws) and the live-mask baker's sources, whose records are pointers, so it calls `LayerOpacity::effective` itself. `canEditOpacity` is one layer, a folder included; `canEditAppearance` stays for blending, so `LayerAppearanceControls` rests with `canEditOpacity` and its Blend caption and picker with `canEditAppearance`; `setSelectedLayersOpacity` dims selected folders too. The format moves to version 8 here (Swift's guides arrive under it in 12.3; until then a version-8 project's `guides` key is ignored as unknown), because 1.2.0's store rule (`d9b3f9e`) lets a folder dim from version 8 on, its blend mode always normal. View ▸ Snap is `snappingEnabled`, a getter and a setter that clears the guides and notifies (Swift's `didSet`); `snappedMove` and the crop drag read it. The transform box draws its accent alone. The effects sheet's sliders span Swift's new ranges (Size 0–20, Distance 0–100, the inner shadow's 0–50, Blur 0–100) while typing and steps reach the effect's own limits (500, 5,000, 500), clamped by `apply`; `QSlider` pins a larger value at its end by itself, so Swift's clamp of the thumb has no twin; the swatch takes a white ring inside a black rim, where SwiftUI's `contentShape` has no need of a twin (a Qt button takes its whole rect). The layer list takes T for Type, as 1.1.6's table does. Equivalent mutant: `canEditOpacity`'s `activeLayer()` term (one selected layer is the active one). `drawPixelGrid` moved to `EditorCanvas+Grid.cpp`, keeping the canvas file under 500 lines. Tests: `FolderOpacityTests` (the walk, the export, the composite, adjustments, effects, the canvas in each way it draws, the baker, Swift's `aDimmedFolderSavesAndReopens`), folder duplication in `LayerDuplicateTests` (moved out of `EditorSessionTests` at 500 lines), `TransformTests` and `LayerDragTests`, the controls in `LayerAppearanceControlsTests`, Snap in `TransformSnapTests`, `CropCanvasTests` and `ViewMenuTests` (the View menu tests, moved out of `CompositorMenusTests`), the ranges and swatch in `EffectsPanelTests`.
- Keyboard shortcuts (12.2b, Swift 1.1.6): `UI/KeyboardShortcuts.h/.cpp` twin Swift's file, `KeyboardShortcuts+Sheet.cpp` its sheet and recorder. `ShortcutChord` keeps Swift's key strings (Backspace 0x7f, Return, Escape, Tab, Space, the arrows as Cocoa's F700s) and modifier bits, Ctrl for Command, Alt for Option, Meta for Control, then Shift; a key event reads Backspace and Delete alike, Enter as Return, Backtab as Tab, a shifted bracket or sign as its own key, anything else by its lowered key name, so a function key's name is long and refused (Swift takes it as a private-use character; known difference); labels are `QKeySequence`'s native text (Ctrl+Alt+K), where Swift prints symbols. `ShortcutDefinition::all` is Swift's list less Hide Compositor, which has no twin; `problem` keeps Swift's rules less its three chords reserved by macOS (the desktop takes its own before the app does). `ShortcutSettings` keeps the overrides in `QSettings` under Swift's `keyboardShortcuts.v1`, as Swift's JSON, a stored set that fails `problem` ignored with a warning on `omaphoto.app` where Swift is silent; `changed()` stands for its observation, and `reload` reads the store again, as a launch does. The menus remember each entry's own key in a property and take `menu` of it on every change. `canvasEvent` and `textEvent` hand back the press to handle, or none to swallow: the canvas (its key handling moved to `EditorCanvas+Keys.cpp`, the navigation file at 500 lines), the layer list and the window's key filter read `canvasEvent`, open text `textEvent`; a translated press the canvas or list leaves passes the original on, as `super.keyDown` does. Swift's `panPhysicalKey` is `m_panKey`: the key whose release ends a remapped pan. `NativeShortcut` is `configuredNativeShortcut`: a `QShortcut` over the sheet and its children clicks its button when that shows (a disabled button refuses `click` by itself); its own plain Return or Escape rests it, leaving the dialogs' default and escape handling, so a field's Return still commits first, while a button moved onto the other's key takes it; a moved original key is swallowed at the sheet; a synthesized press carries Swift's shifted text (`}` for Shift+]), which the brush keys read; `NewCanvasSheet`'s own Return shortcuts rest while Apply is moved; Levels' Preview takes its chord this way, in place of the checkbox's shortcut. The sheet is Swift's: 660 wide, the hint, a search, the three groups of rows with 150-by-26 recorders, the contextual words in Linux's keys, the problem in `BrightText` at 12 pixels only while there is one, Restore Defaults, Cancel and a default Save resting while recording or wrong; a modifier alone keeps recording, and while recording the recorder claims every key, Swift's `performKeyEquivalent`: a `Qt::Tool` panel keeps its parent window's menu shortcuts live, and `QWidget::event` would move the focus on Tab. It opens from the Edit menu, after Paste and a separator, in the `keyboardShortcuts` panel `CompositorMenus` holds. Equivalent mutants: `menu`'s and the Shift branch's `isMenu` terms (menu chords all carry modifiers), `canvasEvent`'s early return without overrides, `m_panKey`'s reset (every pan sets it) and Save's explicit default (its only auto-default button). Tests: `KeyboardShortcutsTests`, `KeyboardShortcutsSheetTests`, `RemappedKeysTests`.
- Guides and the layout grid (12.3a, Swift 1.1.7): `Document/Guides.h/.cpp` twin Swift's `Guides.swift`: `CanvasGuide` (its axis by Swift's raw values, `rawValue` and `guideAxis`), `LayoutGrid` (a namespace), `GuideDrag`, and the session extension, declared in `Guides+Session.h` with the accessors of Swift's view flags (`showsGrid`, `showsGuides`, `showsRulers`, `snapEnabled`, the four Snap To flags, `locksGuides`, each a getter and a setter that notifies, and `guideDrag`), whose state stays in `EditorSession.h`; `guideHitDistance` and `guideColor` are Swift's statics. `finishGuideDrag` takes `removing` where Swift names it `delete`. `canEditGuides` leaves out Swift's `_ = showsBusy`, which only registers an observation. 1.1.7's `snapEnabled` (Snap To's master switch, read by `alignmentSnapTargets` and `snappedGuidePosition`) stands beside 1.1.6's `snappingEnabled` (read by `snappedMove` and the crop drag), as it does in Swift through 1.3.3, with a View entry each. `transformSnapTargets` and `cropSnapTargets` are `alignmentSnapTargets` with and without centres, the canvas's middle after its edges and a layer's between its edges, Swift's order; `TransformSnap::box` (in `Crop.cpp`) is the upright box both files read. The document holds `guides`, equality and undo included; the manifest's optional `guides` is Swift's `Codable` (an array of `id`, `axis` and `position`, left out when there are none, the snapshot writing none for an empty list), and the store refuses guides before version 8 (invalid), more than 1,000 (too large), a repeated id or a position past a million (invalid). `installProject` and `clearProject` drop a drag; `CanvasDocument(snapshot)` loads the guides, so `applyDocumentSize` and `applyImageSize` keep them; the canvas resizer offsets them, the image resizer scales them (a same-size resize keeps them), the canvas flip mirrors those across it. The View menu gains Swift's Show (Grid Ctrl+', Guides Ctrl+;), Rulers (Ctrl+R), Snap (Ctrl+Shift+;), Snap To (Guides, Grid, Layers, Document Bounds), Lock Guides (Ctrl+Alt+;) and Clear Guides, resting without a document or, for Clear, without guides; the five new shortcut definitions join the list. Equivalent mutants: `finishGuideDrag`'s `isNew` test on removal and its `original != position` test (the history drops a step that changes nothing). The rulers, the grid and guides on the canvas and their drags are 12.3b's. Tests: `GuideTests` (Swift's but the canvas drag and the ruler's steps), `ViewMenuTests`, the targets' order in `TransformSnapTests`.
- Rulers, and guides on the canvas (12.3b, Swift 1.1.7): `UI/CanvasRulers.h/.cpp` twin Swift's file: `CanvasRuler::thickness`, `CanvasRulerCorner` and `CanvasRulerView` (a widget per strip, repainting on every `changed()`, where Swift's canvas asks each ruler to redraw), with Swift's `majorStep` and `label`. The canvas is the rulers' sibling, so a ruler maps its points through the screen (`inCanvas`), where Swift reads its own bounds as the canvas's. A press hands the canvas the keys and begins a guide from that ruler (horizontal from the top one), a drag moves it, a release over a ruler drops it; a ruler has no mouse tracking, so it sees no buttonless move and leaves a lost release to the canvas's next press. `ContentView` frames the canvas slot in a grid with the corner and the two strips, shown while `showsRulers` holds and a document is open. `TransformOverlay` draws the layout grid (majors solid gray 0.7 at 45%, subdivisions dotted one point on and two off in gray 0.55 at 28% once four points apart, both a hairline) and the guides (`EditorSession::guideColor`, a hairline across the whole view) first, as Swift's `draw`; the canvas redraws the view when the grid's flag, the guides' flag or the displayed guides change (`GuidesShown`), Swift's observation. Guide drags live in `EditorCanvas+Guides.cpp`: with the Move tool a press on a guide (`canEditGuides` and `hitGuide`) moves it ahead of any layer under the resize cursor of its axis, a drag follows, a release over a ruler (`isOverRuler`: a point left of or above the canvas while the rulers show) deletes it; Escape cancels it ahead of a transform edit's keys; wheels and pinches rest while one is dragged; the Move tool's hover shows the guide's resize cursor after the handles and before a layer's move cursor. Qt can lose a release: a buttonless move and a lost focus finish the drag where it is. Equivalent mutant: the ruler press's `canEditGuides` test (`beginGuideCreation` asks it again). Tests: `GuideCanvasTests` (Swift's `moveToolDragsAGuideAndRulerDropDeletesIt` and `rulerStepUsesNicePixelIntervals`; the drawing, repaints, cursors, keys, lost releases, the rulers' layout, ticks, repaints, focus and drags), the canvas's place in `ContentViewTests`.
- The Magic tool's Object mode (12.4, Swift 1.1.8): `Document/ObjectSelection.h/.cpp` twin Swift's file, `ObjectSelection+Session.h` its session half; `WandMode` (Swift's raw values, `allWandModes`) sits in `Selection.h`. Vision's foreground instances have no Linux twin (the user's decision): `SubjectRemoval::foreground` hands back U²-Net's mask at the image's size (the Remove Background model and cache, 9.7), which `select` scales to the model's 320 grid, cuts at half, and splits into 8-connected regions (`region`, the neighbours a traced outline joins); the region under the clicked cell is the instance, background none, and a picture where the model finds no subject none, as Vision's empty result. Its cells are enlarged smoothly to the image and refined by `GuidedMatte::refine` (radius 5) on the image, for Swift's edge-preserving upsample, then cut at half; `adjusted` erodes or dilates a pixel ring a step (eight neighbours, ten steps at most, the image's edge counting as inside, Swift's `eroded` and `dilated`), `MagicWand::outline` traces it and `smoothed` rounds the stairs as Swift's (the start Qt's close repeats dropped first, since a CGPath's close adds no point, then a subpath under three points dropped, Douglas–Peucker at 1.6 from the leftmost point, Chaikin three times, the fill rule kept; Swift's later drops of a repeated end and Chaikin's guard under three points are dead after that and left out). A `bad_alloc` is `ExportError(render)`; Swift's `unsupported` has no twin. The worker catches `SubjectRemovalError`, `MagicWandError` (the trace's refusals) and `ExportError`, each landing in `brushError` as Swift's `catch`. `selectionSample` is the wand's sample made public as Swift's; `selectObject` runs through the wand's watcher and landing (`Wanding` carries the step's name, `Object Selection`), with a completion callback, the offset clamped to ten either way and the anti-alias setting as its smoothing. `pressWandKey` chooses the tool, W on the canvas and in the list, a repeat ignored; Tab steps the mode; the tool's label, its shortcut definition (`Magic`) and the bar's title say Magic. The bar (`LassoControls`) shows Wand and Object as checkable buttons for Magic alone, the colour wand's controls in Wand mode, and in Object mode This Layer and All Layers and an Edge field of −10 to 10 px (`SelectionAmountField` takes a sign when its range goes below zero; a lone minus changes nothing, an overflow reads as its end), with Swift's help; the anti-alias help follows the mode. The canvas's press runs `selectObject` ahead of the colour wand, a click inside the selection picks afresh, the cursor is the crosshair with `SelectionIcon::objectSelection` (haloed by eight offsets as every selection icon, where Swift strokes it white), and the rail draws the icon for Object mode (`ToolIconKind::object`); the status hint follows the mode. Known difference: U²-Net finds one salient mask, so objects touching in it are one region where Vision may tell instances apart. Left out as dead: the mode picker's `cancelLasso` (Magic never holds a draft: `beginLasso` refuses it and `selectTool` cancels one), `selectObject`'s busy term (`canEditSelection` reads it) and its clamp of the offset (`adjusted` clamps), and a null check of the enlarged cells (`GuidedMatte::refine` checks its own). Equivalent mutants: the grid's cut at exactly 128, `simplifyClosed`'s guard under four points (the fallback returns the same points), `finish`'s three-point threshold at four (a traced loop has four corners), the Chaikin reserve, the edge's rounding (typing and arrows give whole numbers), W calling `selectTool` (`pressWandKey` is that call). Untested failure paths: the region's own 320-cell image, 100 KB, which no limit starves without starving the grid before it, and the worker's `MagicWandError`: a refined mask never nears eight million edges, and the trace's image-sized buffer asks less than the guided filter before it. Tests: `ObjectSelectionTests` (regions, edges, smoothing, the model on red discs, the session, keys, the canvas), the bar in `LassoControlsTests`, the icon sheet, the rail and hints in `ContentViewTests` and `ContentViewStatusTests`.
- Photoshop import (12.5a, Swift 1.2.0): `src/IO/PSD/` twins Swift's `IO/PSD` folder. `PSDTypes` holds `PSDError` (Swift's five cases and words), `PSDConversion`, `PSDRecord`, `PSDDocument` and `fromPSD` (Swift's `LayerBlendMode.fromPSD`); Swift's `PSDLayerKind.other` is never assigned, so the case and its note are left out. `PSDChannelCoder` decodes raw and PackBits planes (a no-op run skipped, every overrun `truncated`) and builds `RGBA8888_Premultiplied` pixels tagged sRGB, rounding as Swift's `(c × a + 127) / 255`, and `Grayscale8` masks; a surface that cannot be allocated is `ExportError(render)` through `BrushRaster::context`, where Swift says `truncated`. `PSDReader` reads Swift's fields in Swift's order over a `Cursor` whose bounds check cannot overflow (an 8B64 length near `qint64`'s top reads as truncated, where Swift's `offset + count` traps), maps the file where it can and reads it where it cannot (a pipe, a mount without `mmap`), as `mappedIfSafe` does (a file that cannot be opened or read is `unreadable`, where Swift passes on the Cocoa error), logs every refusal on `omaphoto.io` and rethrows it. Pascal names are Mac OS Roman through a table of the 128 high code points taken from Python's `mac_roman` (Qt decodes it only through ICU); keys are ASCII or nothing, as Swift's `.ascii`. `PSDAdjustments::parse` (in `PSDReader+Adjustments.cpp`) reads Levels, Curves and Hue/Saturation as Swift does. `PSDVector` draws vector masks with `QPainterPath` (tight `boundingRect`, a path empty only without elements as a `CGPath`), fills by nonzero winding and strokes with `Qt::SvgMiterJoin` at 10, SVG's miter rule being CoreGraphics' (probed: kept to a ratio of 9.57, bevelled from 10.43; `Qt::MiterJoin` measures from the join point and clips instead); `integral` stays in doubles, so a wild box reaches the size check instead of an overflowing `QRect`. `PSDDocumentBuilder` makes the layers and conversions; a shape's identity is its asset's. `ImageImporter::loadPhotoshop` and `photoshopAssets` run on the import's worker, `makeImport` on the UI thread. In the session (`EditorSession+Imports.cpp`) a file whose first bytes are `8BPS` takes the Photoshop path: `beginPSDReading` shows the sheet while a `QFutureWatcher` reads it, `finishPSDReading` fills it or takes it away, `finishConversion` answers from the event loop (a resumed task), Cancel while reading drops the file silently, a failure joins the import's failures, and a confirmed file lands through `insertPhotoshop` (a new canvas at the file's size and resolution, or one folder named for the file inside the active folder, centred on a drop point, 10,000 layers at most). A request of Photoshop files alone is one `Import Photoshop File` step. Fixes beyond Swift: `insertPhotoshop` validates the hierarchy first, so folders nested past its depth refuse the file (`truncated`), and a folder clipped to the layer below takes no link but the base note, where Swift links it; either way Swift admits a document its store refuses. Left out as dead: the gates' `showsConversionSheet` terms and its `didSet` (the sheet shows only while importing, which the gates refuse already), Swift's test hook `confirmConversions`, `confirmPSDConversions` and `NativeLayerList.moveLayer` (no caller), the request's `id`, the builder's folder and adjustment checks on a clipping base (only pixel layers become bases), the reader's `layerSectionEnd`, the default mask colour, the reader's plane-size checks (a plane decodes to its size), resolution's finiteness test and its floor, the vector code's finiteness tests on boxes built from finite numbers and the origination's notes (never set), Curves' two length checks past the first, `pixelSize`'s area in doubles (its boxes are whole, so the whole pixels decide alone), the session's catch around `makeImport` (every image arrives with its asset, so nothing there allocates), and the new folder's removal from the collapsed set (a fresh id is in no set). `UI/PSDConversionSheet` is Swift's sheet in a window-modal `QDialog` (`conversionSheet`) that `ContentView` shows from the session's request: the title at 17 pixels bold, the words, a spinner while reading or the list of layer names over their notes, Cancel and the default confirm button, resting while reading; Escape and the close button cancel, and a sheet the session takes away answers nothing; `open()` makes the dialog window-modal. The request shown is kept, so an unrelated change keeps the content, and replaced content hides at once and is deleted later. The importer's filter and the desktop entry take `.psd` (`image/vnd.adobe.photoshop`); a dropped picture is copied as `Dropped.<suffix>` into a folder of its own, as Swift 1.2.0 keeps a dropped file's name. Equivalent mutants: the cursor's own bounds refusal and `skip`'s (every read past the end meets another refusal: a short signature, a short plane), PackBits' count and row-end checks (the branches refuse the same bytes; they spare reading past the buffer), the `reserve` calls, `painter.end()` before the raster returns, the drop copy's `close()` before its static removal, and the logs. Untested failure path: a read that fails after the file opened (an I/O error; Qt 6.4 refuses to open a directory). Tests: `PSDRoundTripTests` and `PSDVectorTests` (Swift's, through `tests/PSDFixture.h`, Swift's writer, and `PSDVectorFixtures.h`), `PSDReaderTests` and `PSDReaderLayerTests` (the reader's edges, every cut before the last layer byte, budgets and vector layers read whole, built by `PSDReaderFixtures.h` and `PSDVectorBuilders.h`), `PSDImportTests` (the session and the sheet), and the drop, importer, message and desktop checks in their files.
- Outer Glow and brush Smoothing (12.5b, Swift 1.2.0): `OuterGlowEffect` joins the effects with Swift's defaults (20 pixels, white, 75%) and bounds (0–500, 0–1), `LayerEffectKind::outerGlow` ("Outer Glow") last, so the footer's menu, the list's rows and every helper take it; the manifest's `outerGlow` is Swift's `Codable` (`size`, `opacity`, the colour, `enabled` only while set). `LayerEffectsKernel` blurs the shape's coverage at sigma size ÷ 2, Metal's glow buffer (a size under 0.02 copies it, as Swift's zero shift does), and composes it over the drop shadow and under an outside stroke, clamped to glow × (1 − shape) × opacity; the renderer's margin takes three sizes, the stroke surface's reach three sizes and two. Swift's CPU `outerGlowCoverage` serves machines without Metal and is dead here, as the other CPU coverages are (9.6b), so Swift's CPU and Metal parity test has no twin. The preview cache keeps the last preview while one effect is hidden or shown on the same pixels (Swift's `dbe82b0`). A fix beyond Swift: a reduced preview scales the glow's size, as it scales the inner shadow's lengths (9.6c). The sheet shows the glow's swatch, Size (0–100 on the slider, 500 typed, px) and Opacity. Smoothing is Swift's string: `BrushSettings::smoothing` (0–100); while the Brush paints (either mode) with smoothing, the brush (`m_brushAnchor`) moves only once the pointer (`m_brushPointer`) pulls further than smoothing ÷ the viewport's zoom, and then by the excess along the string; the release paints on to the pointer; a cancel drops both. The other brush tools follow the pointer. Equivalent mutants: the press's pointer and the cancel's two resets (each makes the others' work redundant), `>` at the string's exact length (a move of zero), the release's tool and smoothing terms (otherwise it appends the last point again), and the surface's glow reach between the blur's three sigmas and Swift's three sizes. `BrushControls` shows Smoothing for the Brush alone: a 100-point slider in tenths and a 42-point `SelectionAmountField` of 0–100 with Swift's help. The rest of 1.2.0 is held already (TASKS.md 12.0, each note now saying Swift agrees) or not code (`NativeLayerList.moveLayer` has no caller; the spelling touches shader comments), but for two follow-ups of `90ee29f` and `7c4512a`: Select All never rests and reaches a focused layer list (7.1's note), and the invert test holds no wall clock. Tests: `OuterGlowTests` (Swift's, but the parity test), the glow in `LayerEffectsKernelTests`' shader replay, `LayerEffectsSurfaceTests`' rows and `EffectsPreviewCacheTests`' scaling, the kinds, manifest and menu in their files; `BrushSmoothingTests` and the bar in `BrushControlsTests`.
- Camera RAW (12.6a, Swift 1.2.1): Core Image's RAW filter has no Linux twin, so `IO/RawImporter` develops through LibRaw (the user's decision), its thread-safe `libraw_r` found by pkg-config; `Dockerfile.dev` installs `libraw-dev`, the PKGBUILD and the flake depend on `libraw`, the distro images carry it. A RAW is any file whose extension names a type inheriting `image/x-dcraw` in the MIME database (`matches`, `isRawType` for a dropped picture, `globs` for the importer's filter), Swift's `UTType.rawImage`. `RawDevelopSettings` keeps Swift's fields, `isAsShot` and `reset`; `RawDevelopRequest` is Swift's tuple. White balance: `planckian` is Kim et al.'s cubic (1667–25000 K), `whitePoint` moves off the locus along its greener uv normal by tint ÷ 3000, `temperatureOf` inverts it by a mired search and golden sections: Adobe's scale and sign (the DNG SDK's `kTintScale`), so a positive tint is a greener white and turns the picture magenta, and D65 reads about +10, as Lightroom's Daylight. Known difference: CIRAWFilter's temperature and tint follow Apple's own model; these follow Adobe's convention on CIE 1960 uv. `asShot` reads the camera's multipliers (`cam_mul`, else dcraw's daylight `pre_mul`) and turns the neutral into xy through LibRaw's `rgb_cam` (a DNG's `cam_xyz` stays zero) with `pre_mul` put back; `develop` works back from the chosen white to camera multipliers (`user_mul`, the second green the first's), reading the camera's `pre_mul`, `rgb_cam` and size from unpack's copy (`rawdata`), since a process overwrites `color` with its own multipliers and a half-size one halves `sizes`; a white the matrix maps to a response at or below zero is refused, logged, where LibRaw would drop the balance in silence; the refusal is `ImageImportError(whiteBalance)`, a kind of Linux's own with words of its own, since `CIRAWFilter` takes every white and real cameras' matrices reach it inside the sliders (the warm and green corner). It takes LibRaw's 16-bit sRGB at a power of one (linear), with neither auto-brightening nor the maximum's adjustment (`adjust_maximum_thr` 0, so a frame near white keeps its level), clipped at white in camera space (`highlight` 0, so a clipped photosite stays neutral: unclipped, the matrix turns it magenta), where LibRaw divides by the smallest multiplier; the twin multiplies the smallest back, so the balance is anchored on green, as Core Image's, where dcraw alone brightens the frame as the temperature moves. Known difference: where a multiplier falls below green's (the slider's far ends), the frame's white falls to that multiplier. It makes the look itself, rows side by side: exposure multiplies linear light by 2^EV, clamped, then Boost mixes sRGB's curve (0) with LibRaw's BT.709 curve (1). Known difference: Apple's Boost curve is undisclosed; at 1 this is LibRaw's default curve. The result is opaque `RGBA8888_Premultiplied` tagged sRGB, oriented by LibRaw. Only three-colour sensors develop; a four-colour one is `unsupported` (dcraw's matrices hold no fourth to invert). A preview past its limit decodes at half size, then fits smoothly. `Queue` is Swift's actor: one develop at a time under a mutex, the unpacked frame kept for the previews of one file, a full develop always fresh, `release` letting go; Swift keys the cache by the limit too, since its filter's scale is fixed when made, where LibRaw halves per develop. LibRaw's refusals are `unreadable`, logged with its message on `omaphoto.io`; a surface that cannot be made is `ExportError(render)`. In the session (`EditorSession+Imports.cpp`) a RAW goes before the Photoshop check: `pixelSize` (unreadable when it fails) and Swift's budget (`tooLarge` past 30,000 a side or the pixels left), then `developRaw` shows the sheet with the camera's settings (the defaults when they cannot be read) and keeps the answer, `finishRawDevelop` clears the request, releases the queue on a worker and answers from the event loop (a resumed task): nothing skips the file, settings develop the whole frame on the import's worker, which catches `ImageImportError` and `ExportError`, into a layer named for the file. `rawDevelop` alone stands for Swift's `rawDevelop` and `showsRawDevelop`, which are set and cleared together; the latter's `didSet` is dead (the sheet shows only while importing, which holds file requests anyway), and so is the test hook `confirmRawDevelop`. `UI/RawDevelopSheet` is Swift's sheet in a window-modal `QDialog` (`rawDevelopSheet`) that `ContentView` shows while the request stands, its close button and Escape cancelling and a sheet the session takes away answering nothing: the title at 17 pixels bold, the 560 by 340 preview on 35% black rounded 6 with a spinner while a develop runs, four rows (a 90-point title as the buddy of a 300-point slider, the value 80 points wide in `PlaceholderText`: Exposure in hundredths, Temperature and Tint whole, Boost in thousandths, printed as Swift's `%.Nf`), Reset (resting while as shot), Cancel and the default Import. The first preview develops at once, each change after 60 ms (Swift's `task(id:)`), at 800 pixels through the queue on a worker; a newer change drops the older's result, and a failed preview keeps the last one, logged. Left out as dead: LibRaw's size check after identification (`adjust_sizes_info_only` fails only when called before), the second green's multiplier (LibRaw copies the first's), the lower clamp of unsigned samples, and a check of the output's colours and bits (three colours and 16 bits are asked for). Equivalent mutants: a response of exactly zero refused as below zero (a double lands on it only by chance), Import's explicit default (a dialog makes its first auto-default button the default) and the fit at exactly the limit (the scale keeps the size). Untested: a stale preview dropped while a newer one waits is ordered by the test through the wait timer alone. A dropped picture takes a RAW type after Photoshop's; the importer's filter and the desktop entry (`image/x-dcraw`) take RAW. Tests: `RawImporterTests` (matching, the locus and its round trips, the camera's balance, curves, exposure, colour, orientation, the preview's limit, the queue's cache), `RawDevelopTests` (the session, refusals and budgets, a develop that fails, the sheet), a tiny DNG writer in `DNGFixture.h`, the drop order in `ImageFileDropTests`, the filter in `ContentViewTests`, the entry in `DesktopIntegrationTests`. `tests/Tests.cmake` holds the test binaries, keeping `CMakeLists.txt` under 500 lines.
- Middle-button pan, tool defaults, Auto Select and the icon (12.6b, Swift 1.2.1): `Document/ToolDefaults` twins Swift's enum as a namespace: `boolean` (Swift's `bool`, a C++ keyword) and `set` keep Auto Select, the transform controls, the pixel grid, the layout grid, guides, rulers, Snap, the four Snap To switches and Lock Guides in `QSettings` under Swift's `tool.` keys, read by the session's members as they are made and written by each setter, and by the two places that show guides by themselves (`beginGuideCreation`, `addGuide`), as Swift's `didSet` sees those writes. Swift returns the defaults under XCTest; Qt has no such flag, and most test binaries run outside `QStandardPaths`' test mode, so the twin keeps the defaults until `ToolDefaults::enable()`, which `main` calls first (not under test, as the theme's construction is not). The settings file keeps text, so a stored value reads as `true` or `false`; anything else is ignored with a warning on `omaphoto.app`, where Swift's `as? Bool` is silent. The canvas's middle button (Swift's `otherMouseDown` for button 2) pans from any tool while a document is open, on a drag point of its own (`m_middlePanPoint`), so a left drag under way goes on beside it: a move with both buttons pans, then gives the left its turn (so a Hand drag pans twice), and a right-button tip drag waits for the middle's release. Known difference: macOS sends one drag event a motion, so which button Swift's canvas follows then is AppKit's choice. The press hides the brush circle and shows the closed hand, which outranks every other cursor; the release puts the tool's cursor and circle back. Qt can lose a release: a move without the middle button ends the pan. Unlike Swift's `mouseDown`, the press takes no focus. `transformPressLayer` gains Swift's foreground rule: with Auto Select, a press inside the active layer's box goes to the layer under the pointer when that is painted above it (a background holding every press no longer hides the layer on top); `above` reads both layers through checked lookups, since the pointer's layer and the visible active one are both drawn, where Swift guards each index. Swift's `underPointer != active.id` is left out as dead (`above` refuses a layer against itself); equivalent mutant: `>=` in `above` (only the active layer equals itself, and `selectLayer` of the active layer changes nothing). The reshaped app icon (`45ab8fd`) replaces `packaging/icons`. Tests: `ToolDefaultsTests` (the defaults until enabled, every toggle across sessions and as text, guides shown by a guide, a strange value), `theMiddleButtonPansFromAnyTool` in `CanvasNavigationTests`, Swift's `autoSelectPicksForegroundLayerStackedOnSelectedBackground` and a mask box past its layer in `TransformPressTests`, whose older Auto Select test now expects the layer above.
- Photoshop's blend modes (12.7a, Swift 1.2.2): `LayerBlendMode` takes Swift's order, Photoshop's, and `allLayerBlendModes` follows it, so the blend keys step Normal, Darken, Multiply…; the raw values are Swift's (`Linear Dodge (Add)` among them), so the manifest reads them without a new version, as Swift's. `blendGroup` stands for Swift's static `groups`: each group's modes sit together in the enum, so the group is the last first member a mode reaches. `BlendModePicker` draws a separator between groups, as Swift's pop-up does; QComboBox's keys step over them and never make one current, so no preview names one. Hard Light and Exclusion are QPainter's composition modes; the other eight go by hand (`SeparableBlend`, `HslBlend`). The PSD reader takes Swift's new keys (`lbrn`, `lddg`, `hLit`, `vLit`, `lLit`, `pLit`, `hMix`, `smud`, `fsub`, `fdiv`); Dissolve, Darker Color and Lighter Color fall to Normal with the conversion note, and Swift's renamed test uses Dissolve. A fix beyond Swift: Swift's `LiveMaskRenderer` composites a clipping stack's group and an adjustment's result through `cgMode`, which is Normal for the eight (v1.2.2's `prepareStacks`, `drawComposite` and `adjust`, unchanged through 1.3.3), so a base or an adjustment in one of them draws as Normal there; the twin hands every mode to `LayerRenderer::composite`, which blends the eight by hand, as Photoshop composites a clipping group with its base's mode (`ClippingStackTests::aStackBlendsOnceWithItsBasesMode`, `AdjustmentLayerTests::adjustmentBlendAndSoftMaskPreserveCoverage`). Swift's `coreImageFilter` has no twin: `needsSurface` names the modes. Equivalent mutants: `<=` against `<` at one half in Vivid and Pin Light (both branches give the backdrop there). Tests: the formulas in `BlendModeTests`, the menu's groups and keys in `BlendModePickerTests`, the order in `LayerAppearanceTests`, `BlendShortcutTests`, `EditorCanvasTests` and `ProjectManifestTests`, the keys in `PSDRoundTripTests` and `PSDImportTests`, the canvas against the export in `CanvasDisplayTests::photoshopsOwnModesShowAsTheExportDoes`.
- Black & White, Color Balance and Invert (12.7b, Swift 1.2.2): `kernels/AdjustPixels.c/.h` are v1.2.2's, with `adjust_black_white` and `adjust_color_balance`, run through `ImageAdjustmentPixels::run` on one thread as Swift's. `BlackWhiteSettings` and `ColorBalanceSettings` keep Swift's fields, defaults and bounds (the `isFinite` terms left out, as the bounds refuse NaN and infinities); `apply` throws `ProjectError(invalid)` past them and Color Balance hands an untouched image back. Swift's `FilterSettings.normalized` does not clamp either, so a number typed past a slider's range fails the preview with that error and a commit sets `brushError` with no step, as in Swift: the filter's two workers catch `ProjectError` beside their other errors, where it would otherwise escape as `QUnhandledException` and abort. `FilterKind` gains both after Grain (`isImageAdjustment`), `AdjustmentKind` Invert, Black & White and Color Balance in Swift's order, with `isEditable` (all but Invert) and `filterKind`; `LayerAdjustment` gains the two optionals with Swift's computed getter and setter pairs, validity and `apply` (Invert through `PixelInvert::run`, whole image, colour only); the manifest's `blackWhiteSettings` and `colorBalanceSettings` are Swift's synthesized `Codable`, every key required, left out while absent. `addAdjustment` opens the editor for editable kinds alone: an Invert layer applies at once. The editors carry both settings through `beginAdjustmentEditing` and `editedAdjustment`. A fix beyond Swift: Swift's Edit Adjustment… stays enabled on an Invert layer, whose editor switch breaks after the original is kept and the transaction opened, so nothing ever closes them and the session stays refused; the twin's entry rests for a kind that is not editable, and the two switches throw a `logic_error` for Invert, which nothing reaches. As Swift's row, an Invert layer says "Adjustment · Double-click to edit", yet a double click on its glyph renames it (`m_editableAdjustment`, Swift's `isEditable` test). The Image menu lists Black & White… and Color Balance… before Exposure…, the Layer menu's New Adjustment Layer entries take an ellipsis when editable, and a menu doubles the ampersand of "Black & White" (a lone one is a mnemonic in Qt), in the kinds' entries and in Undo and Redo's step names alike; object names drop it (`blackWhite`, `newBlackWhiteAdjustment`). `LayerIcons` draws Swift's three new symbols as paths: `circle.righthalf.filled`, `circle.filled.pattern.diagonalline.rectangle` (a rounded frame, diagonal lines, a filled circle) and `scale.3d` (three axes with arrowheads). The filter sheet's two kinds live in `UI/FilterSheet+Adjustments.cpp` (the sheet's file neared 500 lines): the six families and Tint's Hue and Saturation, shown while Tint is on (Swift's `if`, the rows `m_shownWhen` holds with Advanced's), and Color Balance's three headlines (13 pixels, semibold, Swift's `.headline`, as the effects sheet's) over three rows each and Preserve Luminosity; each `flag` is Swift's `Toggle` with its help as the tooltip. `NativeLayerList` stops listening in its destructor, as `ContentView` does: closing a list window hides it first, and a rename's focus-out then commits into a list half destroyed. Tests: Swift's `invertAppliesWithoutAnEditor` in `AdjustmentLayerTests`, its editor test over the editable kinds in `AdjustmentEditorTests` and `FloatingPanelTests`, `ColorAdjustmentTests` (the kernels against Photoshop's defaults and a tint worked in HSL, the tones of Color Balance and Preserve Luminosity, bounds, every manifest key, the sheet), the kinds, keys and menus in `FilterModelTests`, `LayerAdjustmentTests`, `AdjustmentPanelTests`, `CompositorMenusTests` and `SelectMenuTests`. `ProjectExportFailureTests`' two panel limits rose from 2,048 KB: the thousand-layer snapshot grew by the two optionals of every record (2,560 KB since 12.8d).
- The Camera Raw filter's model (12.8a, Swift 1.2.3): `kernels/AdjustPixels.c/.h` are v1.2.3's, with the Camera Raw kernels and Grain's particle size (`59b5040`); that kernel warns under `-Wunused-parameter` and `-Wmisleading-indentation` through 1.3.3 (both lines date from `9982fad`; `075a71b` fixes another), so CMake silences those two for that file alone. `Document/CameraRaw.h/.cpp`, `CameraRawColor`, `CameraRawDetailOptics` and `CameraRawGeometryCalibration` twin Swift's four files; Swift's `CameraRaw.swift` runs to 638 lines, so its session extension is `CameraRaw+Session.cpp` with `CameraRaw+Session.h`. The enums keep Swift's raw values and order; `CameraRawClipping` keeps Swift's bits (highlights 1, shadows 2); `Balance` and `Gains` are structs for Swift's tuples; `region` returns a reference where Swift writes through a key path. `CameraRawDrag` sits in `CameraRaw.h`, where Swift's sits in `CameraRawColor.swift`: it holds the whole settings, which C++ needs complete. Swift's panel state sits on `FilterEdit` (the shown groups, pages, swatch, point index, the tools, the guide draft, clipping, sharpen mask, the scope and its mode, the readout); the twin gathers it in `CameraRawPanel`, `FilterEdit::rawPanel`, written through `setCameraRawPanel`, which notifies while an edit is open. `renderSettings` is Swift's settings with the hidden groups left out (`applying`); the commit renders and keeps those, so a hidden group stays out next time, and an identity grade closes as Cancel does. `previewJob` carries the panel's views; the preview's worker runs `CameraRawScope::preview`, whose scope lands on the panel. A fix beyond Swift: Swift's `preview` drops the point colour's view (it runs the job itself only for clipping or the sharpen mask, through 1.3.3), so Visualize never shows; the twin runs the job for it too. Geometry's warp is `QTransform::quadToQuad` from the image's rect to Swift's corners flipped to y down, drawn smooth and antialiased; a warp Qt cannot solve is a `logic_error`. Constrain Crop fits the frame inside `brush_alpha_bounds`; a crop whose copy finds no memory is `ExportError(render)`, where Swift's `cropping` returning nil falls back to the uncropped warp. Left out as dead: `apply`'s `isValid` guard and with it `isValid` (settings arrive normalized, and nothing else asks), `nudged`'s guard for an empty channel (`normalized` repairs every curve to two points; `at` throws if that breaks), the vectorscope's wrap of a negative hue (its angle's cosine and sine turn round alike), the parametric curve's `max(0, weight)` (a tone inside its region weighs 0 to 1), each group's `applying(shows:)` (no caller), and the defringe eyedropper's own `normalized` (`updateFilter` normalizes). Equivalent mutants: `tone < shadow` against `<=` (the regions meet with equal weight), the defringe tie's `<` against `<=`, the mixer's `weights > 0` against `>= 0` (a zero weight adds nothing), the identity commit's cancel (the history drops an unchanged step), and Auto's `committing` term (a committing edit refuses `updateFilter`, and the landing asks again). The Filter menu and the sheet leave Camera Raw out until its panel (12.8b). Tests: `CameraRawTests`, `CameraRawSessionTests` (Swift's session tests; the preview's views and scope), `CameraRawToolsTests`, `CameraRawRulesTests`, `CameraRawColorTests`, `CameraRawLensTests` (the kernel's calibration called directly), `CameraRawWiringTests` (Effects, Optics and Detail against their kernels called with the header's order, a clip view on an untouched grade, Auto in linear light, every eye's fields, Offset, Aspect and Constrain Crop against placed pictures, the scope's channels and hues, the curve, mixer and grading call with its floats written out, the sharpen-mask view, each lens flag alone, Grain's scale, a dull colour's reach, Rotate, Scale and Vertical against placed pictures), `CameraRawFixtures.h`, Grain's size in `ImageAdjustmentTests`, the kind in `FilterModelTests`.
- The Camera Raw panel (12.8b1, Swift 1.2.3): Swift docks the filter's `NSPanel` to the document window's right edge, full height, following it (`dockedToMainWindowRight`). Wayland lets no client place a window, and a tiling compositor would tile a second one, so the twin docks inside the window: `FloatingPanel::show` takes a dock slot, `ContentView`'s `panelDock` at the right of the middle row, `FloatingPanel::dockedWidth` (Swift's 440) wide, and there the panel is its own `PanelWindow` made a plain child (`Qt::Widget`), so `QDialog` still takes Escape as Cancel and Return as the default button; a header holds the title and a close button, which cancels. A docked frame is never remembered (`moveEvent` asks `isWindow`), so Gaussian Blur and the rest reopen where they were left, Swift's `dockedPlacementLeavesTheSavedFilterPosition`; `refocus` hands a docked panel the keys through `setFocus`, looking past the hidden floating panel of the same name, which is the window's child too. The dock takes room beside the layers panel and spans the middle row alone, so the tool bar and status bar keep their width, where Swift's panel lies over the window's whole height (known difference). Refocus hands the keys to the docked panel itself, not the field last typed in (known difference: `makeKey` keeps its first responder). `UI/CameraRawSlider` twins Swift's file: `CameraRawSliderTrack` with Swift's colours, the gradient drawn 4 points high across the groove under the style's knob, a double click on the knob (its rect two points out) resetting; a press on the track is `SliderSnap`'s (10.5): Swift's 0.18 s glide has no twin, and a drag goes on from the snapped knob, as every slider of the twin does (known differences); `display` keeps a knob under a drag, Swift's `isTrackingValue`; the track is fixed at construction: Swift's track update in `updateNSView` has no twin, since the rows whose tracks change (12.8b2's mixer) are made anew. `UI/CameraRawControls.h/.cpp` and `CameraRawControls+Basic.cpp` (Light, Color, Effects) twin Swift's view: the scope 110 high on black at 35%, the three ribbons at 55% in SwiftUI's dark red, green and blue (the Levels histogram's values) or the vectorscope's cells, square by the width and counted up from the bottom, so a 110-point graph shows its lowest 18 rows, as Swift's does, its context menu choosing the mode, the two clipping triangles lit in that blue and red, the readout; the words say Alt for Option and a right click for Control-click; the ten groups, Light and Color open, each eye shown while its group adjusts; a row's title (96 points at least, a double click resetting), `CameraRawSlider` and a 56-point `PickerField` showing Swift's `.number` to the row's decimals. A row's object name is its settings field (`vignetteAmountSlider`), since titles repeat. Alt is read from `QGuiApplication::keyboardModifiers`, Swift's `NSEvent.modifierFlags`, and its release (auto-repeat aside), from any window, ends the clipping and sharpen-mask views (Swift's local monitor). Curve to Calibration fill their groups in 12.8b2, and the Filter menu's entry waits for them. On the canvas (`EditorCanvas+CameraRaw.cpp`) a hover reads the readout (Swift's `mouseMoved`, never a drag), leaving clears it, the three eyedroppers sample and hand the panel the keys, the guide and the targeted drag begin, go on and end on release, and a move without the left button ends either, since Qt can lose a release; the four tools are `picking`, so the eyedropper shows. `EyedropperIcon::icon` came from `LevelsSheet`, which shares it. Left out as dead: the canvas's `kind == cameraRaw` and edit terms before the readout (the session asks), a hide of the other placement's panel in `show` (every edit closes its panel first), Swift's clipping reset before a row's reset (`assign` clears it), and the docked panel's own hide on close (its slot hides it). Equivalent mutants: the titles' minimum width, 96 points (a layout sizes labels offscreen alike), and the unlit triangle's 55% white (cosmetic, over whatever the scope shows). Two consequences of the named differences: a double click on a slider's track resets it, since the first press puts the knob under the second; and a canvas press takes the keys, so a field still being typed in commits at the click, where Swift's panel keeps its field editor. Tests: `CameraRawSliderTests` (Swift's three), `CameraRawPanelTests`, `CameraRawCanvasTests` (the dock in a real window among them), `FloatingPanelTests::dockedPlacementLeavesTheSavedFilterPosition`.
- The Camera Raw panel's other groups (12.8b2, Swift 1.2.3): `UI/CameraRawColorControls.h/.cpp` (Curve), `+Mixer.cpp` and `+Grading.cpp`, `UI/CameraRawDetailOpticsControls` and `UI/CameraRawGeometryCalibrationControls` twin Swift's three files, each view a `QWidget` over the session, synchronized on `changed()`. `UI/CameraRawRow` is Linux-only: the row each Swift view builds for itself (`sharpenSlider`, `opticsSlider`, `geometrySlider`, `calibrationSlider`, the curve's and mixer's sliders, 12.8b1's `slider`): a title of at least or exactly a width, `CameraRawSlider`, a field or none, a double click on the title resetting where Swift's main groups do; each view rounds the slider's value as its Swift twin does (Detail to whole numbers, Optics when its range starts at zero, Geometry and Calibration always, the rest not). Swift's segmented pickers are `cameraRawSegments`, touching checkable buttons in an exclusive `QButtonGroup`. The curve graph: a still press and release adds a point, a drag past two points moves the nearest divider or inner point, a double click removes the nearest inner point within 0.04 and its trailing release adds nothing, so the net is Swift's: SwiftUI adds on each click, `repair` drops the second as a duplicate and the double tap removes one. The graph is `CameraRawCurveGraph`: a class defined in a `.cpp` outside an anonymous namespace is global, and the Curves sheet's `CurveGraph` would share its vtable across the link. The mixer's rows whose help or track follow its tab, swatch or chosen point are made anew when those change, as SwiftUI renders them anew; a picked colour's swatch is shown at once, since a layout shows late children only later. The grading wheel fills a `QConicalGradient`, which runs counterclockwise from the right as the hue does (1.2.9's `96edd5f`), takes presses and double clicks inside its circle alone (Swift's `contentShape`), and Swift's `theDockedPanelFitsTheGradingWheels` holds; its stops are 96edd5f's own, pure HSV hues every 30 degrees (v1.2.3's six SwiftUI system colours predate that fix). Detail's idle noise rows are disabled under a 45% `QGraphicsOpacityEffect`, Swift's `.opacity(0.45).disabled`. Targeted Adjustment and Draw Guides are checkable push buttons, checked while armed, where Swift tints them (known difference); their SF Symbols, `scope` and `line.diagonal`, are `LayerIcons` paths. The Filter menu lists Camera Raw Filter… after Lens Correction, as Swift's. Known differences: a mixer family's field still being typed in loses its typing when the tab changes (the row is made anew), where SwiftUI's field would commit into the new tab; Equivalent mutants: the wheel's saturation cap (`normalized` clamps it), the picked swatches made anew only when their count changes (it spares rebuilds; Qt guards a swatch deleted in its own click) and the page menu's size policy (layout). The point-colour eyedropper is flat like the other two, where Swift leaves it bordered (cosmetic). Cosmetic, Swift's values and unpinned: the swatches' 18 points, Detail's idle 45%, the hue ranges' inset (title width and 10), the rows' spacing of 10 and the 11-pixel subheadlines. Tests: `CameraRawRowTable.h` walked by `CameraRawGroupRowsTests` (every row against Swift's values), `CameraRawGroupDrawTests` (drawing, pages, gestures, the panel through `FilterSheet`), `CameraRawGroupWordsTests` (every text, captions, buddies, the pickers' states, the mixer's pages, the wheel's lower half and rim, the curve's line, repaint and selected point), `CameraRawCurveMixerTests`, `CameraRawGradingLensTests`, the menu's entries in `CompositorMenusTests`.
- Hash containers on the render path (12.8e): Qt 6.4 declares `QHashPrivate::Data::findOrInsert` `noexcept` while it allocates, so a `QHash` or `QSet` insert that finds no memory calls `std::terminate`, past every catch (found by a backtrace of `ProjectExportFailureTests` under load: the JPEG worker's render aborted in `LiveMaskGraph::validate`). Code a worker runs under a catch that promises to survive memory running out uses `std::map` and `std::set`, whose inserts throw: `LiveMaskGraph::validate`, `FolderMaskClip::draw` and `LiveMaskRenderer`'s caches (and `LiveMaskBaker::bake` beside `validate`, though its workers catch `ExportError` alone, so a `bad_alloc` there still ends the app, by design), as `ImageExporter::render` already keyed its records. The UI thread's own `QHash`es stay: a failure there ends in Qt's event loop either way. `RenderStarvationTests` replaces `operator new` on its thread and fails each allocation of `validate`, `prepareStacks` and `FolderMaskClip::draw` in turn: each must throw `std::bad_alloc`; the three aborted with the old containers. Painting is left out of it: Qt's painter is not exception-safe, and a failure injected inside it can leave a lock held.
- Blur and noise adjustment layers, Image Trim and Inner Glow (12.8c, Swift 1.2.3: `98ad817`, `24052b5`, `feb39f3`, `cd0ca3c`). `AdjustmentKind` gains Add Noise, Gaussian Blur and Motion Blur after Grain, v1.2.3's order (it moved Add Noise ahead of the blurs), with `circle.dotted`, `drop.fill` and `wind` as `LayerIcons` paths. `LayerAdjustment` keeps Swift's seven optionals (`blurRadius`, `motionAngle`, `motionDistance`, `noiseAmount`, `noiseGaussian`, `noiseMonochromatic`, `noiseSeed`), their resolved getters and setters with Swift's defaults (10, 0, 10, 10, off, off, 0), `isValid`'s bounds on every kind, as Swift's, and `samplingMargin`; the manifest writes each only when set, the seed a `UInt32` read as Grain's; the store takes the three kinds from version 9, which it now writes (versions 1–9). `apply` runs the three through `PixelFilter::run` with the layer's own seed; `FilterJob::noiseOrigin` sits last, so the positional initialisers keep their order, and `kernels/NoisePixels.c` is v1.2.3's (`noise_add_at`, whose position hash reshuffles the Add Noise filter's grain too). A new Add Noise layer rolls its seed, as Grain does; the editor opens the kind's filter panel on the layer's settings and writes back that kind's alone. Adaptation: Swift's canvas surface holds a pixel a point, so its region's origin and `scale` are already the surface's pixels; the twin's surfaces hold device pixels, so `LiveMaskRenderer::adjust` passes `adjustmentScale` (the canvas's zoom, Swift's, 1 elsewhere) times the device's pixels a region unit, and `apply` counts the noise origin in the image's pixels, so a HiDPI canvas blurs at its own density and the noise stays one field across dirty rects. `AdjustmentSurface::draw` takes Swift's `padding` in the painter's units: the halo is allocated past the shown area, not cut to the device (the canvas's outer surface is dirty-sized), and drawn back under the painter's clip. The canvas pads by the widest visible `samplingMargin` times the zoom, and its crisp path (from 200%) now draws the layers through a padded surface as well, as Swift's `drawLayers` wraps its own there. Known difference, Swift's too: on the smooth path the canvas's noise follows the view, as Grain's does; on the crisp path the surface's region starts at the repaint region, so each partial repaint there draws a noise field of its own. The crisp path wraps its surface even without an adjustment, where Swift's `drawLayers` wraps only for one: pixel-identical (source-over onto a cleared raster), one allocation a repaint region, as the smooth path already does. The HiDPI product is pinned by its two factors (the zoom on the canvas, the device ratio on a scaled composite), not at a device ratio of two itself. Image Trim: `Document/ImageTrim` twins Swift's file: `TrimBasedOn` by raw value, `TrimOptions` (a tolerance per premultiplied channel, alpha included, which the sheet leaves at 0), `calculateTrimRect` (the alpha bounds, or each row scanned in from both ends against the corner's pixel) and `trim` (the export's render, then `CanvasResizer` by the content offset, or the snapshot itself when nothing is cut). `UI/TrimSheet` is Swift's sheet: 320 wide, the title, Based On as radio buttons, Trim Away's four checkboxes, OK resting while none is checked, Return and Escape through `NativeShortcut`. `ProjectController::trim` runs as Canvas Size does, through `resizeProject`, whose resize may now return nothing: Swift's trim with nothing left returns with no alert and no step. The Image menu's Trim… follows Image Size…, with no shortcut. Left out as dead: `TrimError` (never thrown), `trimImage` and the session's `trim` (called by Swift's tests alone; the twin tests the rect and the controller's two steps), the kept rect's `maxX > minX` guard (the early returns leave content, so left < right and top < bottom) and the colour scan's `last > first` (the row's first unmatched pixel stops it). A fix beyond Swift: a raster that cannot be converted is `ExportError(render)`, explained, where Swift's `try?` reports nothing left; that failure path is untested, since only a failed allocation reaches it. Inner Glow joins as Outer Glow did (12.5b): `InnerGlowEffect` (10 pixels, white, 75%; 0–500, 0–1), `LayerEffectKind::innerGlow` last; `LayerEffectsKernel` blurs the shape at sigma size ÷ 2 and keeps shape × (1 − blur), composed over the colour overlay and under the inner shadow, Metal's order; no margin (Swift's `innerGlowRendersInsideSourceWithoutBoundsExpansion`), the stroke surface's reach three sizes and two. Swift's CPU `innerGlowCoverage` is dead here, as Outer Glow's is, so its parity test has no twin. A fix beyond Swift: a reduced preview scales the glow's size. The sheet shows its swatch, Size (0–100, 500 typed, px) and Opacity. Equivalent mutants: the canvas's margin counting hidden layers (it only widens the halo), the glow's `opacity > 0` (a clear glow composes nothing; the term spares the blur) and Trim's return of an uncut snapshot (the canvas resizer returns one unchanged at the same size and place). The padding branch keeps an unpadded surface to the shown pixels: mapped there and back, a rect rounds a pixel wider. Tests: `BlurNoiseAdjustmentTests` (the model, manifest, store, seeds, the editor, the filters at a scale, the noise field, a scaled target, the canvas's zoom and a partial repaint's halo at 100%, 150% and 400%), `ImageTrimTests` (Swift's six, tolerance, the sheet, the controller through its sheet, a failure's alert), `InnerGlowTests` (Swift's, but the parity test, and the order), the new kinds in `LayerAdjustmentTests`, `AdjustmentEditorTests`, `AdjustmentLayerTests` and `AdjustmentPanelTests`, the glow in `LayerEffectsKernelTests`' replay, `LayerEffectsSurfaceTests`, `EffectsPreviewCacheTests`, `LayerEffectsTests` and `EffectsPanelTests`, version 9 across the store's tests, Trim in `CompositorMenusTests`.
- Drops between projects: `ProjectWorkspace::draggedLayerSource` finds the tab whose document holds the dragged id (Swift reads the drag pasteboard; the twin reads the drag's `QMimeData`, which every drop target has), `canReceiveDrag(data, destination)` refuses only a layer's own tab, and `receiveProviders` copies several ids one after another, as Swift awaits each provider, so a two-row drop on the New button opens two tabs as Swift's does. `ContentView` takes such a drop over its whole area (`setWorkspace` hands it the workspace; `acceptsDrop` keeps Swift's guards: busy, the sheet, the importer, a rename; `levels` arrives with 9.x), shows the 3-point accent ring inside the canvas while targeted and hands the drop's document point on when it fell on the canvas. `ProjectTabButton` takes drops for its tab (accent fill and rim, "Add to <title>"), and `NewCanvasButton`, the toolbar's New canvas button with the action as its default, for a fresh tab ("Open in a new project tab"), both refusing an Alt drag, which duplicates in the panel; Swift's transient `NewTabDropSlot` in the strip has no twin, the New canvas button is `NewProjectDropTarget` already. Files and pictures arrived with 10.4.
- `CanvasThumbnail` draws a layer or a mask inside the canvas's box at `backingScale` 2 (the panel's pixmaps carry that ratio); a mask's ground is the mean of its edge pixels, as Swift's `edgeTone`. `LayerIcons` draws the panel's SF Symbols as paths, in one palette colour, like `ToolIcons`. `BlendModePicker` is a `QComboBox` whose popup previews the highlighted mode through `previewBlendMode` for the layer it opened on (Qt calls `hidePopup` before `activated`, so the preview, the target and the highlight are cleared from the event loop, after a choice had its chance) and refuses a choice once another layer is active. `LayerAppearanceControls` is Swift's blend and opacity row: the slider's press and release are one opacity drag (the release is watched application-wide while the slider is down, so a popup opened mid-drag cannot keep the step open), the percent field applies once through its `FocusOut`, which Return and Escape cause (Swift's `releasesFocusOnCommit`), and steps with Up and Down (Swift's `isFinite` test and the steps' clamp are left out: `setLayerOpacity` refuses a value that is no finite number and clamps the rest), and another active layer makes the controls anew, as Swift's `.id` does.
- `ProjectWorkspaceView` is the `QMainWindow`: the front tab's `ContentView` as its central widget, made anew when another tab comes to the front, as SwiftUI's `.id` rebuilds it, and disabled while the workspace manages; the window holds the shown tab (`std::shared_ptr`) until the old editor is deleted, as Swift's views hold their session, so a replaced or closed tab's session never ends under its editor (`ProjectWorkspace::tab` is public for this); a `QToolBar` with the New canvas action, the `ProjectTabStrip`, a spacer and the four zoom actions, since SwiftUI's `.toolbar` modifier lives in `ContentView` but the toolbar belongs to the window. Its actions follow the front session's `changed()`, and on that signal the window syncs every tab's button as well, because a busy front tab dims the other tabs' buttons, which their own sessions' signals do not reach; the strip syncs its buttons on the workspace's signal, each button on its own session's. The window's title is the front tab's, with Qt's `[*]` placeholder, so `setWindowModified` can show the mark that `isDocumentEdited` shows; `setWindowFilePath` carries `representedURL`. The editor's own minimum size is cleared inside the window, which owns the 800 × 520 minimum for the whole, toolbar included. Closing the window ignores the event and asks the workspace (`closeWindow`), which confirms tab by tab and then closes the window again with the property `closeConfirmed` set, since the workspace may not include `UI/` headers; a confirmed close is accepted and the mark cleared, so a window shown again asks again. `ProjectTabStrip` is a `QScrollArea` whose buttons are kept for the tabs that stay, moved for the tabs that moved, made for new tabs and deleted for tabs that went; its row is sized to its tabs by hand (a resizable scroll area would squeeze every title below Swift's 35 points) and resized again whenever a title changes, and the front tab scrolls into view at once; it and its viewport fill no background, so the toolbar shows through as Swift's mask lets it (a stylesheet would do the same but freezes the widgets' palette, so a theme switch would pass them by); the unsaved dot is a character before the title. Files named on the command line go to `ProjectWorkspace::receive`, as Finder's Open With reaches the delegate. Layer drops on tabs and the New canvas button are 4.7's; file and picture drops arrived with 10.4.
- `CompositorMenus` builds the window's `QMenuBar` from Swift's `.commands`, entry for entry, as far as the session functions exist (`TASKS.md`, "Menu items owed", lists the rest); ⌘ is Ctrl and ⌥ is Alt in every shortcut. Its entries follow the front tab's session, like the toolbar. Swift's Undo and Redo keep a text field's own undo while one has focus, so the twin's do the same: with a `QLineEdit` in focus the entries are the field's, titled bare and always enabled; otherwise they carry the step's name, and only while the session's history is usable. Focus is state the session does not announce, so the menus also sync on `QApplication::focusChanged`. Keyboard navigation (Alt+E) hands focus to the menu bar itself, so the menus keep the field that held it until focus lands anywhere else. The View menu's Pixel Grid entry is checkable and follows `showsPixelGrid`. `Close Project` closes the tab (Swift's `close(window)` hands over to the workspace); `Delete Layer` is Swift's `deleteLayerOrMask`, which takes a chosen effect first since 9.6a; since 9.6d its title names that effect (`Delete Stroke`). The `Hide` entries and `Check for Updates` have no twin (the desktop hides windows; distro packages update).
- The session's gates (`canEditLayers`, `canUseHistory`) and its `selectLayer`, `selectTool`, `undo` and `restore` read only the state that exists so far. `TASKS.md` lists, under "Session hooks owed", the term each later item adds. `reorderLayers` takes a `std::set<int>` for `IndexSet` and reproduces SwiftUI's `move(fromOffsets:toOffset:)`.
- `LayerMask::clipImage` returns nil when the placed grid cannot be rendered, as Swift's `try?` does, and logs a warning on `omaphoto.rendering` so the loss is visible.
- `Rendering/SeparableBlend` twins Swift's file for the modes QPainter lacks since 1.2.2: `needsSurface` names Linear Burn, Linear Dodge (Add), Vivid Light, Linear Light, Pin Light, Hard Mix, Subtract and Divide, and `channel` is Photoshop's formula for each on one channel (in Vivid Light a zero divisor is infinity, clamped to the end; Divide by black is white, zero over zero included, a choice of the twin's, since neither Photoshop nor Core Image publishes it). Swift reaches Core Image's filters, in sRGB as Color Burn and Dodge have been since 1.2.0 (`121a15f`); Color Burn and Dodge themselves stay QPainter's, which follow the PDF formulas, as do its Hard Light and Exclusion (`BlendModeTests::everyBlendModeMatchesThePdfFormulas` holds all twenty-four modes within 2/255 against formulas written apart). Known difference: Core Image's code is not published, so its edges (Hard Mix exactly at one, a divisor of zero) follow Photoshop's definitions, not measured Core Image. Hard Mix is Photoshop's at full fill, white where backdrop and source reach one together.
- `Rendering/HslBlend` is Linux-only: the modes QPainter lacks (Hue, Saturation, Color and Luminosity, and since 1.2.2 `SeparableBlend`'s eight), blended by hand over a copy of the backdrop with the PDF's compositing, so every path that hands a mode to `HslBlend::handles` (the export, the canvas's surface, live masks, effects) takes the new ones.
- Known difference: CoreGraphics enlarges "High quality" layers with a sharper kernel; QPainter offers bilinear only, so `InterpolationQuality::high` and `low` draw alike when enlarging. Reductions are sharp on both (halvings).
- Where an Apple framework threads internally (vImage, Core Image, Metal), the twin threads with QtConcurrent.
- A Swift error enum becomes an exception class with a `Kind` enum; `what()` carries the Swift `errorDescription`.
- `@Observable` classes stay plain C++ where only `EditorSession` mutates them; the session notifies the UI.

Deliberate name breaks: `MetalBrushCoverage` → `BrushCoverage`, `MetalLayerEffects` → `LayerEffectsKernel`.

## Linux-only behaviour

- Tool icons: SF Symbols have no Linux twin, and icon themes differ by distro, so `src/UI/ToolIcons` draws each tool's icon as paths in an 18-point square, in one colour that the caller takes from the palette (the Omarchy theme retints them for free). Swift's two hand-drawn icons keep their geometry there (`GradientToolIcon`'s Floyd–Steinberg fade, `CloneStampToolIcon`'s four parts); their Swift homes (`GradientControls`, `BrushControls`) arrive later. The eyedropper's glyph lives in `Rendering/EyedropperIcon`, since the canvas's cursor draws it too. Icons that follow tool state (ellipse marquee, polygonal lasso, eraser) arrive with that state. `tests/fixtures/ToolIcons.png` is the reference sheet: `ToolIconTests` redraws it, allows a font a few pixels and a stroke none, and writes the fresh sheet beside the test binary; after a wanted change, look at it and commit it.
- Omarchy theme: `src/UI/OmarchyTheme` reads `~/.local/state/omarchy/current/theme/colors.toml` (Omarchy 4.x: flat `key = "value"` lines, `mode` dark or light, the twenty-two stock themes' keys required, `orange` optional and `yellow` its stand-in) into `OmarchyColors`, applies them as the application palette (Window and Text from `background` and `foreground`, Base from `darker_background`, Button from `lighter_background`, Highlight and Link from `accent` with the background as highlighted text, PlaceholderText from `dark_foreground`, BrightText from `orange` or `yellow`, Mid from `muted`, the disabled roles from `muted`) and sets the Fusion style, which follows a palette on every desktop where a platform style does not; no stylesheet is needed. Keys and values read in double or single quotes. A missing key, or a recognised key whose value is bare or half-quoted or no `#rrggbb`, refuses the file with the key's name; a file that exists but cannot be opened, or sits behind a folder that cannot be searched (`stat` fails other than `ENOENT`), is refused too; either way the app keeps the palette it has and logs a warning, where an absent file means the built-in dark, Swift's grays, installed before the first load. `omarchy-theme-set` removes `current/theme`, moves `next-theme` in and writes `theme.name`, so the watcher holds `current/`, `current/theme` and the file, adds them back after each load (a removed path leaves a `QFileSystemWatcher`) and renews the file's watch every load (it follows the inode, which an atomic replacement swaps), watches the nearest ancestor the watcher accepts while `current/` is missing or barred, letting it go once the directory is watched, and loads once 100 ms after the last event. A read that stops short (an error, or fewer bytes than the file holds) is refused like a malformed file. Each load logs the theme's name and mode on `omaphoto.app`. `main` makes the theme before the window. Widgets take colours from the palette, never from literals; the canvas keeps Swift's document grays. The UI font stays Qt's default: `omarchy font current` is not followed.
- No updater. Distro packages own updates.
- Distribution (11.4b): releases live on GitHub under fixed asset names (`omaphoto-noble_amd64.deb`, `omaphoto-resolute_amd64.deb`, `omaphoto.x86_64.rpm`, `omaphoto-x86_64.pkg.tar.zst`; 1.0.0 had one DEB, `omaphoto_amd64.deb`) with `SHA256SUMS`, so `releases/latest/download/<name>` always reaches the newest. `scripts/install/fedora.sh` and `arch.sh` read `/etc/os-release` (`ID` or `ID_LIKE`; Omarchy says `ID_LIKE=arch`) and `ubuntu.sh` its `UBUNTU_CODENAME`, which Ubuntu's derivatives set to their base: each DEB names its release's Qt libraries (24.04's carry a `t64` suffix that 26.04's drop, and Debian 13 has neither), so the release carries one DEB per LTS, built on it (`Dockerfile.dev` takes the base as `BASE`), and the script takes the one whose codename matches, `noble` or `resolute`, refusing any other. Each refuses another system or another machine than x86_64, verify the package against the sums and install it with apt, dnf or pacman under sudo, so the package manager resolves dependencies; apt reads the file as its own user, so the download folder is opened to it. Fedora's script names RPM Fusion's `libheif-freeworld` when it is missing, since Fedora's libheif decodes no HEVC, and adds no repository itself. `nixos.sh` installs the flake at the newest release's tag, which GitHub's `releases/latest` redirect names, into the user's profile (`nix profile install`, the name every Nix still takes), so no user builds unreleased work from `main`. The README runs each script after downloading it, so the package manager's questions read the terminal and fish runs it too. `release.yml` builds each package with the command the distro checks use, the DEBs on the dev image over each base, the RPM on Fedora 43, the oldest Fedora still supported, whose Qt symbols a later Fedora keeps, the Arch package through `makepkg` as a user; the version is CMake's `project` version, the PKGBUILD's and the flake's, kept equal by hand, and the workflow's first job refuses a tag that names another.
- Remove Background runs an open-licensed model on ONNX Runtime.
- A `.comp` project is a directory on Linux; its layout matches the macOS package.
- Shortcuts map ⌘ to Ctrl and ⌥ to Alt.

## Commands

No sudo is needed. Docker does the work.

- `scripts/dev.sh build` — configure and build in the Ubuntu 24.04 container, warnings as errors. With no `CMAKE_BUILD_TYPE` the build is `RelWithDebInfo`: pixel code must stay optimized. Every target is compiled with `_GLIBCXX_ASSERTIONS`: an empty `std::optional` or a bad index aborts, in the tests and in the app, where it would otherwise pass by luck.
- `scripts/dev.sh test` — build, then run every test headless (`QT_QPA_PLATFORM=offscreen`). `HOME` and `/tmp` sit on a tmpfs, as in the distro checks: the store's syncs on the container's disk wait on a busy host.
- `scripts/dev.sh run` — build, then run the app on the host Wayland display (issues #1 and #2, 11.4e): the home folder is mounted at its own path with `HOME` pointing there, so files, settings and the Omarchy theme resolve as in a native run, and each `/dev/dri/renderD*` passes with its group, since Mesa's EGL fails without one (Zink's Vulkan and the dri2 screen). On NVIDIA's own driver the container's Mesa cannot drive the node and EGL still warns; the app paints on the CPU either way. The reporter's black and stale areas cleared with the node; this host never showed them.
- `scripts/mutate.py FILE [--targets T1,T2]` — mutation runner, run from the repository root. Reads `old ==> new` blocks separated by `@@` lines on stdin, or with `--delete [--from N --to M]` removes each statement line in turn. A mutant counts as caught only when it builds and a test fails. Run it on every item before review.
- `scripts/heic-fixtures.sh` — rewrites the HEIC test fixtures in a throwaway container that has `heif-enc` and x265. Its parts are real files under `scripts/heic-fixtures/` (`Dockerfile`, `sources.cpp`, `generate.sh`), so lint reads each in its own language.
- `scripts/lint.py` — the house rules, from the repository root: every file under 500 lines, every comment one line and at most ten words. Each file is read by a scanner for its own language: C++ (`//` and `/* */` outside literals), Python (its own tokenizer), CMake (`#` outside quotes, escapes and bracket arguments, which open only where an argument begins, tracked as state through escapes; bracket comments too), Docker (any line that begins with `#`) and shell. The shell scanner reads the subset the scripts keep to (quotes, escapes, `$( )` and `${ }` to any depth, here-strings, `#` where a word begins) and refuses the rest by name and line, so nothing passes unread: `<<` (a heredoc or a shift), backticks, `$'…'`, arithmetic, `((`, `case` inside `$( )`, and a continued line anywhere but between words (it could split `$(`, `<<` or a keyword). Write scripts inside that subset. A file of any other kind under `scripts` fails lint. It reads `src`, `tests`, everything under `scripts`, `CMakeLists.txt` and `Dockerfile.dev`. `--self-test` checks the checker. Run both before every review.

## Code rules

Fail fast. No silent fallbacks. Fix causes. Log key paths through `QLoggingCategory` (`src/Logging.h`). No dead code. Files stay under 500 lines. Comments: one line, ten words at most, only when needed. No abstraction layers, no reserved extension points. Tests assert concrete values and fail when the code breaks. Tests read a returned `std::optional` through `.value()`, never `*` or `->`: an empty one must fail the test, not read stale memory. Code reads a found element through a checked form, a layer by `indexOf` and `[]`, a map by `at`: when its guard is lost the read aborts or throws, where an iterator at `end()` reads wild memory and the tests pass by luck (`_GLIBCXX_ASSERTIONS` checks `[]`, not iterators).