Bug 678607 - Work around Apple bug to avoid crashing with two-finger swipe on OS X Lion. r=bgirard

widget/src/cocoa/nsChildView.mm

@@ -306,6 +306,15 @@ nsresult nsChildView::Create(nsIWidget *aParent,
   if (!gChildViewMethodsSwizzled) {
     nsToolkit::SwizzleMethods([NSView class], @selector(mouseDownCanMoveWindow),
                               @selector(nsChildView_NSView_mouseDownCanMoveWindow));
+#ifdef __LP64__
+    if (nsToolkit::OnLionOrLater()) {
+      nsToolkit::SwizzleMethods([NSEvent class], @selector(addLocalMonitorForEventsMatchingMask:handler:),
+                                @selector(nsChildView_NSEvent_addLocalMonitorForEventsMatchingMask:handler:),
+                                PR_TRUE);
+      nsToolkit::SwizzleMethods([NSEvent class], @selector(removeMonitor:),
+                                @selector(nsChildView_NSEvent_removeMonitor:), PR_TRUE);
+    }
+#endif
 #ifndef NP_NO_CARBON
     TextInputHandler::SwizzleMethods();
 #endif
@@ -5092,3 +5101,48 @@ ChildViewMouseTracker::WindowAcceptsEvent(NSWindow* aWindow, NSEvent* aEvent,
 }
 
 @end
+
+#ifdef __LP64__
+// When using blocks, at least on OS X 10.7, the OS sometimes calls
+// +[NSEvent removeMonitor:] more than once on a single event monitor, which
+// causes crashes.  See bug 678607.  We hook these methods to work around
+// the problem.
+@interface NSEvent (MethodSwizzling)
++ (id)nsChildView_NSEvent_addLocalMonitorForEventsMatchingMask:(unsigned long long)mask handler:(id)block;
++ (void)nsChildView_NSEvent_removeMonitor:(id)eventMonitor;
+@end
+
+// This is a local copy of the AppKit frameworks sEventObservers hashtable.
+// It only stores "local monitors".  We use it to ensure that +[NSEvent
+// removeMonitor:] is never called more than once on the same local monitor.
+static NSHashTable *sLocalEventObservers = nil;
+
+@implementation NSEvent (MethodSwizzling)
+
++ (id)nsChildView_NSEvent_addLocalMonitorForEventsMatchingMask:(unsigned long long)mask handler:(id)block
+{
+  if (!sLocalEventObservers) {
+    sLocalEventObservers = [[NSHashTable hashTableWithOptions:
+      NSHashTableStrongMemory | NSHashTableObjectPointerPersonality] retain];
+  }
+  id retval =
+    [self nsChildView_NSEvent_addLocalMonitorForEventsMatchingMask:mask handler:block];
+  if (sLocalEventObservers && retval && ![sLocalEventObservers containsObject:retval]) {
+    [sLocalEventObservers addObject:retval];
+  }
+  return retval;
+}
+
++ (void)nsChildView_NSEvent_removeMonitor:(id)eventMonitor
+{
+  if (sLocalEventObservers && [eventMonitor isKindOfClass: ::NSClassFromString(@"_NSLocalEventObserver")]) {
+    if (![sLocalEventObservers containsObject:eventMonitor]) {
+      return;
+    }
+    [sLocalEventObservers removeObject:eventMonitor];
+  }
+  [self nsChildView_NSEvent_removeMonitor:eventMonitor];
+}
+
+@end
+#endif // #ifdef __LP64__