[iamnbutler]

Adds modifier keys and multi-point paths to desktop_drag, from the "Not supported" bullet in docs/tools.md.

peekaboo-drag-path.patch goes last in the stack, after peekaboo-sck-quarantine.patch.

Tool

• modifiers (command, control, option, shift, each at most once) are held for the whole drag: Option-drag to copy or Command-drag to move in Finder, or Shift to constrain.
  • Held keys are system-wide, and Finder's drag session reads the real keyboard state, so a drag with modifiers always takes the foreground route, even within one window. It moves the real pointer, holds the real keys from before the press until after the release, and returns unknown.
  • The modifiers use Peekaboo's existing global drag, which already posts HID modifier key down and up events around the drag.
• path: 1–16 normalized points in the same screenshot, visited in order in straight segments.
  • It works in the background route and, with modifiers, in the foreground route within one window. It's refused with to_snapshot.
  • With a path, to may equal from (a closed loop).
  • Every path point must be uncovered for foreground drags.
• Docs: the desktop_drag row, the pointer paragraph and the "Not supported" bullet are updated.

Patch (peekaboo-drag-path.patch)

• DragPolyline.samples gives each segment at least one sample, shares the rest by segment length, and lands exactly on each waypoint. A straight drag samples the same points as before.
• ExactWindowDragRequest gets waypoints; a missing key decodes as empty. Validation refuses more than 16 waypoints, points outside the window, or fewer samples than segments. Its sample count and dispatched unit count are unchanged.
• DragOperationRequest and PeekabooBridgeDragRequest get waypoints. GestureService.drag follows the samples instead of its movement profile when waypoints are given.
• Sample counts: the client uses max(20, segments × 4), capped at 96, for the background route, and adds segments × 4 as a floor for the foreground one.

Tests

• ExactWindowHeldPointerLifecycleTests: 33 pass, 5 of them new (waypoint samples and unit count, refusals, closed loop, decoding without waypoints, polyline sampling). Run in the foreground with a temporary coordination root.
• npm run check and the native build pass.

Live check: pending (screen locked). Two things need a live check:

• Finder Option-drag copy and Command-drag move.
• Shift-constrain in a drawing app.