During app launch, mouseMoved events can trigger hitTest on the drag
handle while SwiftUI is still modifying view state in a layout pass.
The previous blacklist approach (only deferring mouseMoved, cursorUpdate,
nil) let unexpected event types slip through — e.g. activation events
where NSApp.currentEvent is not the mouseMoved being routed — causing
contentView.hitTest() to re-enter SwiftUI views and trigger an exclusive
access violation.
Switch to a whitelist: only leftMouseDown (the sole event the drag
handle actually handles) proceeds with the full view-hierarchy walk.
All other event types bail out immediately. The deferred-event check
runs after suppression recovery (which uses only ObjC associated-object
calls, safe from Swift exclusivity) so stale suppression is still
cleared on passive events, but before the view-hierarchy walk that
triggered the crash.
Fixes#490
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
1217ba3295