Say why a brush cannot paint; paint at the layer's own resolution; Cancel and Apply only when an edit waits, scaled layers' scale (13.11)

src/Document/BlurTool+Session.h

@@ -1,4 +1,4 @@
 // Swift's BlurTool extension: what a Blur stroke paints.
 public:
-    // The active layer, or its mask, softened at document size.
-    std::optional<QImage> blurSample(const CanvasDocument &document, bool mask = false) const;
+    // The stroke's pixels or mask softened, in its own grid.
+    std::optional<BrushStroke::Clone> blurSample(const BrushStroke &stroke) const;

src/Document/BlurTool.cpp

@@ -2,49 +2,39 @@
 #include "Document/PixelAdjust.h"
 #include "IO/ImageExporter.h"
 #include "Logging.h"
-#include "Rendering/LayerRenderer.h"
 #include <cmath>
 
-// Swift's BlurTool extension: the layer, or its mask, softened.
-std::optional<QImage> EditorSession::blurSample(const CanvasDocument &document, bool mask) const
+// Swift's BlurTool extension: the layer's pixels, or mask, softened.
+std::optional<BrushStroke::Clone> EditorSession::blurSample(const BrushStroke &stroke) const
 {
-    const std::optional<ImageLayer> layer = activeLayer();
-    if (!layer)
+    const ImageLayer &layer = stroke.layer;
+    const std::optional<ImportedImage> &asset = stroke.isMask ? (layer.mask ? std::optional(layer.mask->asset) : std::nullopt) : layer.asset;
+    if (!asset)
         return std::nullopt;
-    // The softening follows the brush's size.
-    const double sigma = std::min(30.0, std::max(1.5, m_brushSettings.diameter / 10));
+    // The canvas's softening carried into the layer's pixels.
+    const QTransform &map = stroke.pixelToDocument;
+    const double perPixel = std::max(1e-6, std::sqrt(std::abs(map.m11() * map.m22() - map.m12() * map.m21())));
+    const double sidePixels = std::max(stroke.sourceRect.width(), stroke.sourceRect.height());
+    const double sigma = std::min(std::min(30.0, std::max(1.5, m_brushSettings.diameter / 10)) / perPixel, sidePixels / 2);
+    // Room for the blur to spread past the pixels' edges.
+    const double margin = std::ceil(3 * sigma);
+    const QRectF region = stroke.sourceRect.adjusted(-margin, -margin, margin, margin);
+    // A huge layer's sample is made coarser, within several canvases.
+    const qint64 canvas = m_document ? qint64(m_document->width) * m_document->height : 0;
+    const double budget = double(std::min(DocumentLimits::maxSurfacePixels, std::max<qint64>(16'000'000, 4 * canvas)));
+    const double fit = std::min(1.0, std::sqrt(budget / (region.width() * region.height())));
+    const int width = std::max(1, int(std::ceil(region.width() * fit))), height = std::max(1, int(std::ceil(region.height() * fit)));
+    const QRectF placed(margin * fit, margin * fit, stroke.sourceRect.width() * fit, stroke.sourceRect.height() * fit);
     try {
-        if (mask) {
-            if (!layer->mask)
-                return std::nullopt;
-            QImage context = BrushRaster::context(document.width, document.height, true);
-            // Past its pixels a mask keeps its edge tone.
-            const int tone = int(std::round(LayerMask::background(layer->mask->asset.thumbnail) * 255));
-            context.fill(QColor(tone, tone, tone));
-            QPainter painter(&context);
-            // Coverage only adds white: the mask's area starts black.
-            const LayerTransform placement = layer->maskTransform();
-            painter.save();
-            QTransform box;
-            box.translate(placement.center().x(), placement.center().y());
-            box.rotateRadians(placement.radians());
-            painter.setTransform(box, true);
-            painter.fillRect(QRectF(-placement.size.width() / 2, -placement.size.height() / 2, placement.size.width(), placement.size.height()),
-                             Qt::black);
-            painter.restore();
-            LayerRenderer::drawCoverage(layer->mask->asset.image(), placement, painter);
-            painter.end();
-            return PixelAdjust::gaussianBlur(context, sigma, true);
-        }
-        if (!layer->asset)
-            return std::nullopt;
-        QImage context = BrushRaster::context(document.width, document.height, false);
+        QImage context = BrushRaster::context(width, height, stroke.isMask);
+        // Past its pixels a mask keeps its edge tone.
+        if (stroke.isMask && layer.mask)
+            context.fill(int(std::round(LayerMask::background(layer.mask->asset.thumbnail) * 255)));
         QPainter painter(&context);
         // A painted asset flattens here; the catch covers it too.
-        const LayerTransform transform = displayedTransform(*layer);
-        LayerRenderer::draw(layer->asset->image(), transform, transform.center(), painter, {});
+        BrushRaster::draw(asset->image(), placed, painter);
         painter.end();
-        return PixelAdjust::gaussianBlur(context, sigma, false);
+        return BrushStroke::Clone{PixelAdjust::gaussianBlur(context, sigma * fit, stroke.isMask), region, true};
     } catch (const ExportError &error) {
         qCWarning(lcApp) << "the Blur tool cannot sample the layer:" << error.what();
         return std::nullopt;

src/Document/BrushStroke+Commit.cpp

@@ -58,6 +58,14 @@ LayerTransform BrushStroke::transform(const QRectF &bounds) const
     return result;
 }
 
+// Offset into grid pixels, turned and scaled as the layer.
+QRectF BrushStroke::gridRect(const QRectF &rect, QSizeF offset) const
+{
+    const QTransform toGrid = pixelToDocument.inverted();
+    const QPointF shift = toGrid.map(QPointF(offset.width(), offset.height())) - toGrid.map(QPointF(0, 0));
+    return rect.translated(-shift);
+}
+
 // Swift's heal: the painted spot rebuilt from nearby texture.
 void BrushStroke::heal()
 {

src/Document/BrushStroke+Stroke.cpp

@@ -273,11 +273,12 @@ QImage BrushStroke::clonePixels(const Tile &tile) const
     if (!clone)
         return QImage();
     const int width = int(tile.rect.width()), height = int(tile.rect.height());
-    // Tile pixels to clone pixels: grid, document, then offset.
-    const QTransform toClone = QTransform::fromTranslate(tile.rect.left(), tile.rect.top()) * pixelToDocument
-        * QTransform::fromTranslate(clone->offset.width(), clone->offset.height());
     // Colour even for gray clones: edges carry their coverage.
     const QImage &image = clone->image;
+    // Tile pixels to clone pixels: grid, maybe document, then placed.
+    const QRectF &placed = clone->placed;
+    const QTransform toClone = QTransform::fromTranslate(tile.rect.left(), tile.rect.top()) * (clone->inGrid ? QTransform() : pixelToDocument)
+        * QTransform::fromTranslate(-placed.left(), -placed.top()) * QTransform::fromScale(image.width() / placed.width(), image.height() / placed.height());
     if (toClone.type() > QTransform::TxTranslate) {
         // Swift's medium quality: bilinear under a scale or turn.
         QImage sample = BrushRaster::context(width, height, false);

src/Document/BrushStroke.h

@@ -107,10 +107,11 @@ public:
     qint64 pixelLimit = DocumentLimits::documentPixelBudget();
     // Limits every edit to the document selection; nil when none.
     std::optional<SelectionClip> selectionClip;
-    // Clone Stamp: a document-sized image, and each point's offset.
+    // Painted through the tip, placed: document or `inGrid` pixels.
     struct Clone {
         QImage image;
-        QSizeF offset;
+        QRectF placed;
+        bool inGrid;
     };
     std::optional<Clone> clone;
     // Blur: the clone is the layer softened, in place.
@@ -144,6 +145,8 @@ public:
     QRectF committedBounds() const;
     LayerTransform committedTransform() const;
     LayerTransform transform(const QRectF &bounds) const;
+    // `rect` shifted to copy from `offset` document pixels away.
+    QRectF gridRect(const QRectF &rect, QSizeF offset) const;
     // Spot Healing's end: the painted spot rebuilt from around it.
     void heal();
     PaintSnapshot paintSnapshot() const;

src/Document/CloneStamp+Session.h

@@ -6,5 +6,5 @@ public:
     std::optional<QSizeF> cloneStrokeOffset(QPointF point) const;
     // The source for a brush at `point`: the canvas's crosshair.
     std::optional<QPointF> cloneSamplePoint(QPointF point) const;
-    // What a stroke copies from, document-sized, taken as it starts.
-    std::optional<QImage> cloneSample(const CanvasDocument &document) const;
+    // What `stroke` copies, `offset` away: its pixels or the canvas.
+    std::optional<BrushStroke::Clone> cloneSample(const CanvasDocument &document, const BrushStroke &stroke, QSizeF offset) const;

src/Document/CloneStamp.cpp

@@ -1,7 +1,6 @@
 #include "Document/EditorSession.h"
 #include "IO/ImageExporter.h"
 #include "Logging.h"
-#include "Rendering/LayerRenderer.h"
 #include <cmath>
 
 // Swift's CloneStamp extension: the source, its offset, the sample.
@@ -40,20 +39,20 @@ std::optional<QPointF> EditorSession::cloneSamplePoint(QPointF point) const
     return point + QPointF(m_cloneOffset->width(), m_cloneOffset->height());
 }
 
-std::optional<QImage> EditorSession::cloneSample(const CanvasDocument &document) const
+std::optional<BrushStroke::Clone> EditorSession::cloneSample(const CanvasDocument &document, const BrushStroke &stroke, QSizeF offset) const
 {
     try {
+        // A painted asset flattens here; the catch covers it too.
+        if (!m_cloneSettings.sampleAllLayers) {
+            if (!stroke.layer.asset)
+                return std::nullopt;
+            return BrushStroke::Clone{stroke.layer.asset->image(), stroke.gridRect(stroke.sourceRect, offset), true};
+        }
         QImage context = BrushRaster::context(document.width, document.height, false);
         QPainter painter(&context);
-        // A painted asset flattens here; the catch covers it too.
-        if (m_cloneSettings.sampleAllLayers) {
-            drawLiveComposite(document, painter);
-        } else if (const std::optional<ImageLayer> layer = activeLayer(); layer && layer->asset) {
-            const LayerTransform transform = displayedTransform(*layer);
-            LayerRenderer::draw(layer->asset->image(), transform, transform.center(), painter, {});
-        }
+        drawLiveComposite(document, painter);
         painter.end();
-        return context;
+        return BrushStroke::Clone{context, QRectF(-offset.width(), -offset.height(), context.width(), context.height()), false};
     } catch (const ExportError &error) {
         qCWarning(lcApp) << "Clone Stamp cannot sample the canvas:" << error.what();
         return std::nullopt;

src/Document/EditorSession+Brush.cpp

@@ -37,6 +37,27 @@ bool EditorSession::canPaint() const
         && (m_isMaskSelected || !layer->adjustment);
 }
 
+std::optional<QString> EditorSession::paintRefusal() const
+{
+    const std::optional<ImageLayer> layer = activeLayer();
+    if (!canEditLayers() || !layer || canPaint())
+        return std::nullopt;
+    if (m_selectedLayerIDs.size() > 1)
+        return QStringLiteral("Several layers are selected. Select just one to paint on it.");
+    if (layer->isGroup && !m_isMaskSelected)
+        return QStringLiteral("“%1” is a folder, which has no pixels of its own. Paint on a layer inside it, or on the folder’s mask.").arg(layer->name);
+    if (!m_document->effectiveVisibleIDs().contains(layer->id))
+        return QStringLiteral("“%1” is hidden, or inside a hidden folder. Show it to paint on it.").arg(layer->name);
+    if (m_isMaskSelected && !(layer->mask && layer->mask->isEnabled))
+        return QStringLiteral("The layer mask is turned off. Shift-click its thumbnail to turn it on, then paint.");
+    if (!m_isMaskSelected && layer->adjustment)
+        return QStringLiteral("“%1” is an adjustment layer, with no pixels to paint. Paint on its mask instead.").arg(layer->name);
+    const std::optional<DocumentSelection> current = selection();
+    if (current && current->isEmpty())
+        return QStringLiteral("Nothing is selected, so there’s nowhere to paint. Choose Select › Deselect (Ctrl+D) to paint anywhere.");
+    return std::nullopt;
+}
+
 // A tiled raster edit of pixels or mask, within budget.
 std::unique_ptr<BrushStroke> EditorSession::makeRasterEdit(const ImageLayer &layer, const BrushSettings &settings, bool growsMask) const
 {
@@ -74,28 +95,20 @@ void EditorSession::beginBrush(QPointF point)
     }
     // Spot Healing and Clone Stamp rework pixels, never a mask.
     const bool paintsMasks = m_tool == NavigationTool::brush || m_tool == NavigationTool::blur;
-    if ((!paintsMasks && (!isBrushTool(m_tool) || m_isMaskSelected)) || !canPaint())
+    if (!paintsMasks && (!isBrushTool(m_tool) || m_isMaskSelected))
         return;
+    if (!canPaint()) {
+        setBrushError(paintRefusal());
+        return;
+    }
     const ImageLayer layer = activeLayer().value();
-    std::optional<BrushStroke::Clone> clone;
+    std::optional<QSizeF> sourceOffset;
     if (m_tool == NavigationTool::cloneStamp) {
-        const std::optional<QSizeF> offset = cloneStrokeOffset(point);
-        if (!offset) {
+        sourceOffset = cloneStrokeOffset(point);
+        if (!sourceOffset) {
             setBrushError(QStringLiteral("Alt-click where Clone Stamp should copy from first."));
             return;
         }
-        const std::optional<QImage> image = cloneSample(m_document.value());
-        if (!image)
-            return;
-        m_cloneOffset = offset;
-        clone = BrushStroke::Clone{*image, *offset};
-    }
-    // Blur paints a softened copy of the layer, in place.
-    if (m_tool == NavigationTool::blur) {
-        const std::optional<QImage> image = blurSample(m_document.value(), m_isMaskSelected);
-        if (!image)
-            return;
-        clone = BrushStroke::Clone{*image, QSizeF(0, 0)};
     }
     finishOpacityEdit();
     try {
@@ -108,9 +121,21 @@ void EditorSession::beginBrush(QPointF point)
             settings.green = settings.red;
             settings.blue = settings.red;
         }
-        m_brushStroke = makeRasterEdit(layer, settings, m_tool == NavigationTool::brush);
-        m_brushStroke->clone = clone;
-        m_brushStroke->isBlur = m_tool == NavigationTool::blur;
+        std::unique_ptr<BrushStroke> stroke = makeRasterEdit(layer, settings, m_tool == NavigationTool::brush);
+        if (sourceOffset) {
+            stroke->clone = cloneSample(m_document.value(), *stroke, *sourceOffset);
+            if (!stroke->clone)
+                return;
+            m_cloneOffset = sourceOffset;
+        }
+        // Blur paints a softened copy of the layer, in place.
+        if (m_tool == NavigationTool::blur) {
+            stroke->clone = blurSample(*stroke);
+            if (!stroke->clone)
+                return;
+        }
+        stroke->isBlur = m_tool == NavigationTool::blur;
+        m_brushStroke = std::move(stroke);
         m_brushStroke->append(point);
         m_brushAnchor = point;
         m_brushPointer = point;

src/Document/EditorSession+Brush.h

@@ -1,6 +1,8 @@
 // Swift's EditorSession+Brush extension: a stroke from press to commit.
 public:
     bool canPaint() const;
+    // Why the target refuses a stroke; none while busy.
+    std::optional<QString> paintRefusal() const;
     std::unique_ptr<BrushStroke> makeRasterEdit(const ImageLayer &layer, const BrushSettings &settings = BrushSettings(), bool growsMask = false) const;
     void beginBrush(QPointF point);
     void continueBrush(QPointF point);

src/Document/Gradient.cpp

@@ -35,8 +35,13 @@ void EditorSession::setGradientSettings(const GradientSettings &settings)
 void EditorSession::beginGradient(QPointF point)
 {
     const std::optional<ImageLayer> layer = activeLayer();
-    if (m_tool != NavigationTool::gradient || !(canPaint() || m_gradientEdit) || !layer)
+    if (m_tool != NavigationTool::gradient || !layer)
         return;
+    // Swift explains only past this guard, where nothing refuses.
+    if (!canPaint() && !m_gradientEdit) {
+        setBrushError(paintRefusal());
+        return;
+    }
     // A new line on this target replaces the pending one.
     if (m_gradientEdit && m_gradientEdit->raster->layer.id == layer->id && m_gradientEdit->raster->isMask == m_isMaskSelected) {
         m_gradientEdit->start = point;

src/Document/Selection.cpp

@@ -420,5 +420,7 @@ void EditorSession::invertSelection()
     const std::optional<DocumentSelection> current = selection();
     if (!m_document || !current)
         return;
-    setSelection(DocumentSelection{canvasPath(*m_document).subtracted(current->path), current->antialiased, current->feather}, QStringLiteral("Inverse"));
+    const DocumentSelection inverse{canvasPath(*m_document).subtracted(current->path), current->antialiased, current->feather};
+    // The inverse of everything is no selection, as Photoshop's.
+    setSelection(inverse.isEmpty() ? std::nullopt : std::optional(inverse), QStringLiteral("Inverse"));
 }

src/Document/SmudgeLiquify.cpp

@@ -196,8 +196,7 @@ void EditorSession::beginWarp(QPointF point)
 {
     const std::optional<ImageLayer> layer = activeLayer();
     if (!canPaint() || m_isMaskSelected || !layer || !layer->asset || !m_document) {
-        if (m_isMaskSelected)
-            setBrushError(QStringLiteral("Smudge and Liquify work on a layer's pixels, not its mask."));
+        setBrushError(m_isMaskSelected ? std::optional(QStringLiteral("Smudge and Liquify work on a layer's pixels, not its mask.")) : paintRefusal());
         return;
     }
     finishOpacityEdit();
@@ -235,7 +234,7 @@ void EditorSession::finishWarp()
                 settings.hardness = 1;
                 settings.opacity = 1;
                 const std::unique_ptr<BrushStroke> stroke = makeRasterEdit(current, settings);
-                stroke->clone = BrushStroke::Clone{warp->image(), QSizeF(0, 0)};
+                stroke->clone = BrushStroke::Clone{warp->image(), QRectF(QPointF(0, 0), warp->image().size()), false};
                 stroke->replacesWithClone = true;
                 stroke->editName = rawValue(warp->mode);
                 for (const QPointF step : warp->points())