Interaction · Pointer: resize, turn, band selection, and gpui's own drag

Resizable sizes a box from its right and bottom edges and a grip at
its corner, within its least and greatest size; the grip is a Tab stop
whose arrows resize a step. Rotatable turns an svg to its angle inside
a ring whose knob a drag moves, Shift snapping to 15 degrees, with the
arrows turning it a notch. SelectionArea selects items with a band
drawn on empty space, a press, Command or Shift to add, and a cursor
the arrows walk with Space to add or drop; Escape clears and
Command-A takes all. The gallery shows gpui's own drag and drop, drag
preview, double press and wheel zoom, with pointers for Sortable,
LongPress and PanZoom; pinch stays blocked, gpui 0.2.2 forwards no
magnify event.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

AGENTS.md

@@ -51,7 +51,8 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - gpui 0.2.2 panics on a deferred draw inside another. Whatever draws over the page goes through `primitives::raise`: at the top it defers; inside something raised it lays out on its own and draws last there, so a list opened in a dialog lies over the dialog. A raise takes its owner's id and draws under it, so its keyed state and focus hold while other raises come and go. `scripts/check.sh` refuses gpui's `deferred` anywhere else.
 - `occlude()` blocks the pointer for everything painted before it, its own ancestors too. Put it on the outermost box that should stop the pointer, as the toast stack does, or the ancestors' hover never fires.
 - A drag that pans, turns or slides goes through gpui's drag, whose moves reach the owner in or out of its box; `on_mouse_move` stops at the box's edge. gpui sends a drag's moves to every listener of its type, so each payload carries its owner's `EntityId` and handlers check it.
-- gpui 0.2.2 paints pictures without a transform, so a picture turns by its pixels: `media::turn` turns decoded frames by quarter turns off the main thread, an asset keyed by the picture and the turn.
+- gpui 0.2.2 paints pictures without a transform, so a picture turns by its pixels: `media::turn` turns decoded frames by quarter turns off the main thread, an asset keyed by the picture and the turn. An svg turns to any angle through its `Transformation`, so a control that turns shows one (`interaction::Rotatable`).
+- A box that keeps a cursor over its items rings the item the cursor is on, not the box, as SelectableList marks its row (`interaction::SelectionArea`).
 - A component that takes a starting value from its owner keeps it in `layout::seeded`: a new value from the owner replaces local drags. A field that reports its words as they change keeps what it sent, so the owner's echo leaves the caret alone (`mail::SignatureEditor`). A cursor inside a seeded view stays while it lies in what is shown, so the owner's echo of a turn leaves it (`calendar::CalendarMonthView`, `YearView`).
 - The capture harness turns on reduced motion, so shots are still: repeating motion rests on one frame, and a shimmer shows no band. gpui's mac window stops its display link while occluded, so a capture advances a moving picture only on the draws the harness forces.
 - Each capture pass starts its page fresh (`Gallery::fresh`): page state lives under the pass, so the dark pass runs its script from the same start as the light one.