From 5b54c352edbc597ec5283bc9cfdd77906350161f Mon Sep 17 00:00:00 2001
From: Timur Pocheptsov <timur.pocheptsov@theqtcompany.com>
Date: Thu, 21 Apr 2016 10:02:17 +0200
Subject: [PATCH] Cocoa integration - add a protection against dangling
 pointers
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Backport watcher-sentinel trick (QPointer->QObject) from dev.

Task-number: QTBUG-42059
Change-Id: I9b2c7cde635c2ed9a3f667f216da62870d0b5ccb
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
---
 src/plugins/platforms/cocoa/qcocoawindow.h  | 6 ++++++
 src/plugins/platforms/cocoa/qcocoawindow.mm | 6 ++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/plugins/platforms/cocoa/qcocoawindow.h b/src/plugins/platforms/cocoa/qcocoawindow.h
index 05e6cf3c9e..e60ca196ac 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.h
+++ b/src/plugins/platforms/cocoa/qcocoawindow.h
@@ -66,6 +66,7 @@ typedef NSWindow<QNSWindowProtocol> QCocoaNSWindow;
     QCocoaWindow *_platformWindow;
     BOOL _grabbingMouse;
     BOOL _releaseOnMouseUp;
+    QPointer<QObject> _watcher;
 }
 
 @property (nonatomic, readonly) QCocoaNSWindow *window;
@@ -315,6 +316,11 @@ public: // for QNSView
     };
     QHash<quintptr, BorderRange> m_contentBorderAreas; // identifer -> uppper/lower
     QHash<quintptr, bool> m_enabledContentBorderAreas; // identifer -> enabled state (true/false)
+
+    // This object is tracked by a 'watcher'
+    // object in a window helper, preventing use of dangling
+    // pointers.
+    QObject sentinel;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index e4cd57a115..12e85c5205 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -94,6 +94,7 @@ static bool isMouseEvent(NSEvent *ev)
         // make sure that m_nsWindow stays valid until the
         // QCocoaWindow is deleted by Qt.
         [_window setReleasedWhenClosed:NO];
+        _watcher = &_platformWindow->sentinel;
     }
 
     return self;
@@ -102,7 +103,7 @@ static bool isMouseEvent(NSEvent *ev)
 - (void)handleWindowEvent:(NSEvent *)theEvent
 {
     QCocoaWindow *pw = self.platformWindow;
-    if (pw && pw->m_forwardWindow) {
+    if (_watcher && pw && pw->m_forwardWindow) {
         if (theEvent.type == NSLeftMouseUp || theEvent.type == NSLeftMouseDragged) {
             QNSView *forwardView = pw->m_qtView;
             if (theEvent.type == NSLeftMouseUp) {
@@ -141,7 +142,7 @@ static bool isMouseEvent(NSEvent *ev)
     if (!self.window.delegate)
         return; // Already detached, pending NSAppKitDefined event
 
-    if (pw && pw->frameStrutEventsEnabled() && isMouseEvent(theEvent)) {
+    if (_watcher && pw && pw->frameStrutEventsEnabled() && isMouseEvent(theEvent)) {
         NSPoint loc = [theEvent locationInWindow];
         NSRect windowFrame = [self.window convertRectFromScreen:[self.window frame]];
         NSRect contentFrame = [[self.window contentView] frame];
@@ -157,6 +158,7 @@ static bool isMouseEvent(NSEvent *ev)
 - (void)detachFromPlatformWindow
 {
     _platformWindow = 0;
+    _watcher.clear();
     [self.window.delegate release];
     self.window.delegate = nil;
 }