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Fix drag-handle crash on launch from stale foreign-window events (#490) (#620)

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Add window-identity check to windowDragHandleShouldCaptureHit so stale
leftMouseDown events from other apps (Finder, Dock) during launch don't
trigger the SwiftUI hierarchy walk while initial layout is mutating.
Add NSLock to breadcrumb limiter for thread safety. Update existing
tests to pass eventWindow for window-attached drag handles.
This commit is contained in:
Lawrence Chen 2026-02-27 01:42:17 -08:00 • committed by GitHub
parent c70ac25eef
commit 2202044af4
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GPG key ID: B5690EEEBB952194
2 changed files with 112 additions and 26 deletions
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63
Sources/WindowDragHandleView.swift
View file

@ -11,9 +11,13 @@ private func windowDragHandleEventTypeDescription(_ eventType: NSEvent.EventType
}
private enum WindowDragHandleBreadcrumbLimiter {
private static let lock = NSLock()
private static var lastEmissionByKey: [String: CFAbsoluteTime] = [:]
static func shouldEmit(key: String, minInterval: CFTimeInterval) -> Bool {
lock.lock()
defer { lock.unlock() }
let now = CFAbsoluteTimeGetCurrent()
if let previous = lastEmissionByKey[key], (now - previous) < minInterval {
return false
@ -55,17 +59,27 @@ private func windowDragHandleEmitBreadcrumb(
sentryBreadcrumb(message, category: "titlebar.drag", data: data)
}
private func windowDragHandleShouldDeferHitCapture(for eventType: NSEvent.EventType?) -> Bool {
switch eventType {
case .leftMouseDown?:
private func windowDragHandleShouldResolveActiveHitCapture(
for eventType: NSEvent.EventType?,
eventWindow: NSWindow?,
dragHandleWindow: NSWindow?
) -> Bool {
// We only need active hit resolution for titlebar mouse-down handling.
// During launch, NSApp.currentEvent can transiently point at a stale
// leftMouseDown from outside this window (for example Finder/Dock
// activation). Treat those as passive events so we never walk SwiftUI/
// AppKit hierarchy while initial layout is mutating it.
guard eventType == .leftMouseDown else {
return false
default:
// Only left-mouse-down needs the full view-hierarchy walk.
// All other events (mouseMoved, cursorUpdate, activation, nil, …)
// bail out immediately so we never re-enter SwiftUI views during
// a layout pass — which causes exclusive-access crashes (#490).
}
guard let dragHandleWindow else {
// Test-only views may not be attached to a window.
return true
}
guard let eventWindow else {
return false
}
return eventWindow === dragHandleWindow
}
/// Runs the same action macOS titlebars use for double-click:
@ -210,19 +224,22 @@ func windowDragHandleShouldTreatTopHitAsPassiveHost(_ view: NSView) -> Bool {
func windowDragHandleShouldCaptureHit(
_ point: NSPoint,
in dragHandleView: NSView,
eventType: NSEvent.EventType? = NSApp.currentEvent?.type
eventType: NSEvent.EventType? = NSApp.currentEvent?.type,
eventWindow: NSWindow? = NSApp.currentEvent?.window
) -> Bool {
let dragHandleWindow = dragHandleView.window
// Suppression recovery runs first so stale depth is cleared even for
// passive events — the associated-object reads/writes here are pure ObjC
// runtime calls and cannot trigger Swift exclusive-access violations.
if isWindowDragSuppressed(window: dragHandleView.window) {
if isWindowDragSuppressed(window: dragHandleWindow) {
// Recover from stale suppression if a prior interaction missed cleanup.
// We only keep suppression active while the left mouse button is down.
if (NSEvent.pressedMouseButtons & 0x1) == 0 {
let clearedDepth = clearWindowDragSuppression(window: dragHandleView.window)
let clearedDepth = clearWindowDragSuppression(window: dragHandleWindow)
windowDragHandleEmitBreadcrumb(
"titlebar.dragHandle.suppression.recovered",
window: dragHandleView.window,
window: dragHandleWindow,
eventType: eventType,
point: point,
minInterval: 20,
@ -237,7 +254,7 @@ func windowDragHandleShouldCaptureHit(
#endif
} else {
#if DEBUG
let depth = windowDragSuppressionDepth(window: dragHandleView.window)
let depth = windowDragSuppressionDepth(window: dragHandleWindow)
dlog(
"titlebar.dragHandle.hitTest capture=false reason=suppressed depth=\(depth) point=\(windowDragHandleFormatPoint(point))"
)
@ -248,11 +265,17 @@ func windowDragHandleShouldCaptureHit(
// Bail out before the view-hierarchy walk so we never re-enter SwiftUI
// views during a layout pass — which causes exclusive-access crashes (#490).
if windowDragHandleShouldDeferHitCapture(for: eventType) {
if !windowDragHandleShouldResolveActiveHitCapture(
for: eventType,
eventWindow: eventWindow,
dragHandleWindow: dragHandleWindow
) {
#if DEBUG
let eventTypeDescription = eventType.map { String(describing: $0) } ?? "nil"
let eventWindowNumber = eventWindow?.windowNumber ?? -1
let dragWindowNumber = dragHandleWindow?.windowNumber ?? -1
dlog(
"titlebar.dragHandle.hitTest capture=false reason=passiveEvent eventType=\(eventTypeDescription) point=\(windowDragHandleFormatPoint(point))"
"titlebar.dragHandle.hitTest capture=false reason=passiveEvent eventType=\(eventTypeDescription) eventWindow=\(eventWindowNumber) dragWindow=\(dragWindowNumber) point=\(windowDragHandleFormatPoint(point))"
)
#endif
return false
@ -300,7 +323,7 @@ func windowDragHandleShouldCaptureHit(
#endif
windowDragHandleEmitBreadcrumb(
"titlebar.dragHandle.hitTest.blockedBySiblingHit",
window: dragHandleView.window,
window: dragHandleWindow,
eventType: eventType,
point: point,
minInterval: 8,
@ -335,7 +358,13 @@ struct WindowDragHandleView: NSViewRepresentable {
override var mouseDownCanMoveWindow: Bool { false }
override func hitTest(_ point: NSPoint) -> NSView? {
let shouldCapture = windowDragHandleShouldCaptureHit(point, in: self)
let currentEvent = NSApp.currentEvent
let shouldCapture = windowDragHandleShouldCaptureHit(
point,
in: self,
eventType: currentEvent?.type,
eventWindow: currentEvent?.window
)
#if DEBUG
dlog(
"titlebar.dragHandle.hitTestResult capture=\(shouldCapture) point=\(windowDragHandleFormatPoint(point)) window=\(window != nil)"