QNSView: Harden logic around platform window access

Some users have reported crashes in -[QNSView mouseEnteredImpl:]
which we believe are due to null m_platformWindow. The stack
traces are like the one below or similar:

    0 libqcocoa_dylib   QNSView                 mouseEnteredImpl_ 0x1F
    1 appkit            NSTrackingArea          _dispatchMouseEntered_ 0xA2
    2 appkit            NSApplication           sendEvent_ 0xF4D
    3 libqcocoa_dylib   QNSApplication          sendEvent_ 0x4E
    4 libqcocoa_dylib   QCocoaEventDispatcher   processEvents 0x184
    5 qtcore            QEventLoop              exec 0x19C
    6 qtwidgets         QDialog                 exec 0x20B

Moreover, since 2f505b79a4, that
member is a QPointer, so we should do more systematic checks.

Change-Id: Iced447515a4ae07a62734e587f5b08d46d313071
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/plugins/platforms/cocoa/qnsview.mm

@@ -238,6 +238,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 
 - (void)viewDidMoveToSuperview
 {
+    if (m_platformWindow.isNull())
+        return;
+
     if (!(m_platformWindow->m_viewIsToBeEmbedded))
         return;
 
@@ -258,6 +261,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 
 - (QWindow *)topLevelWindow
 {
+    if (m_platformWindow.isNull())
+        return nullptr;
+
     QWindow *focusWindow = m_platformWindow->window();
 
     // For widgets we need to do a bit of trickery as the window
@@ -273,6 +279,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 
 - (void)updateGeometry
 {
+    if (m_platformWindow.isNull())
+        return;
+
     QRect geometry;
 
     if (self.window.parentWindow) {
@@ -619,6 +628,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 
 - (void)handleMouseEvent:(NSEvent *)theEvent
 {
+    if (m_platformWindow.isNull())
+        return;
+
     // Tablet events may come in via the mouse event handlers,
     // check if this is a valid tablet event first.
     if ([self handleTabletEvent: theEvent])
@@ -633,6 +645,8 @@ static bool _q_dontOverrideCtrlLMB = false;
         else
             m_platformWindow->m_forwardWindow.clear();
     }
+    if (targetView->m_platformWindow.isNull())
+        return;
 
     // Popups implicitly grap mouse events; forward to the active popup if there is one
     if (QCocoaWindow *popup = QCocoaIntegration::instance()->activePopupWindow()) {
@@ -657,6 +671,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 
 - (void)handleFrameStrutMouseEvent:(NSEvent *)theEvent
 {
+    if (m_platformWindow.isNull())
+        return;
+
     // get m_buttons in sync
     // Don't send frme strut events if we are in the middle of a mouse drag.
     if (m_buttons != Qt::NoButton)
@@ -936,6 +953,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 
 - (void)mouseMovedImpl:(NSEvent *)theEvent
 {
+    if (m_platformWindow.isNull())
+        return;
+
     if ([self isTransparentForUserInput])
         return;
 
@@ -967,6 +987,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 - (void)mouseEnteredImpl:(NSEvent *)theEvent
 {
     Q_UNUSED(theEvent)
+    if (m_platformWindow.isNull())
+        return;
+
     m_platformWindow->m_windowUnderMouse = true;
 
     if ([self isTransparentForUserInput])
@@ -986,6 +1009,9 @@ static bool _q_dontOverrideCtrlLMB = false;
 - (void)mouseExitedImpl:(NSEvent *)theEvent
 {
     Q_UNUSED(theEvent);
+    if (m_platformWindow.isNull())
+        return;
+
     m_platformWindow->m_windowUnderMouse = false;
 
     if ([self isTransparentForUserInput])
@@ -1012,6 +1038,9 @@ Q_GLOBAL_STATIC(QCocoaTabletDeviceDataHash, tabletDeviceDataHash)
 
 - (bool)handleTabletEvent: (NSEvent *)theEvent
 {
+    if (m_platformWindow.isNull())
+        return false;
+
     NSEventType eventType = [theEvent type];
     if (eventType != NSTabletPoint && [theEvent subtype] != NSTabletPointEventSubtype)
         return false; // Not a tablet event.
@@ -1170,6 +1199,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (bool)shouldSendSingleTouch
 {
+    if (m_platformWindow.isNull())
+        return true;
+
     // QtWidgets expects single-point touch events, QtDeclarative does not.
     // Until there is an API we solve this by looking at the window class type.
     return m_platformWindow->window()->inherits("QWidgetWindow");
@@ -1177,6 +1209,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)touchesBeganWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     const NSTimeInterval timestamp = [event timestamp];
     const QList<QWindowSystemInterface::TouchPoint> points = QCocoaTouch::getCurrentTouchPointList(event, [self shouldSendSingleTouch]);
     qCDebug(lcQpaTouch) << "touchesBeganWithEvent" << points;
@@ -1185,6 +1220,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)touchesMovedWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     const NSTimeInterval timestamp = [event timestamp];
     const QList<QWindowSystemInterface::TouchPoint> points = QCocoaTouch::getCurrentTouchPointList(event, [self shouldSendSingleTouch]);
     qCDebug(lcQpaTouch) << "touchesMovedWithEvent" << points;
@@ -1193,6 +1231,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)touchesEndedWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     const NSTimeInterval timestamp = [event timestamp];
     const QList<QWindowSystemInterface::TouchPoint> points = QCocoaTouch::getCurrentTouchPointList(event, [self shouldSendSingleTouch]);
     qCDebug(lcQpaTouch) << "touchesEndedWithEvent" << points;
@@ -1201,6 +1242,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)touchesCancelledWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     const NSTimeInterval timestamp = [event timestamp];
     const QList<QWindowSystemInterface::TouchPoint> points = QCocoaTouch::getCurrentTouchPointList(event, [self shouldSendSingleTouch]);
     qCDebug(lcQpaTouch) << "touchesCancelledWithEvent" << points;
@@ -1228,6 +1272,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 }
 - (void)magnifyWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     if ([self handleGestureAsBeginEnd:event])
         return;
 
@@ -1242,6 +1289,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)smartMagnifyWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     static bool zoomIn = true;
     qCDebug(lcQpaGestures) << "smartMagnifyWithEvent" << zoomIn;
     const NSTimeInterval timestamp = [event timestamp];
@@ -1255,6 +1305,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)rotateWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     if ([self handleGestureAsBeginEnd:event])
         return;
 
@@ -1268,6 +1321,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)swipeWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     qCDebug(lcQpaGestures) << "swipeWithEvent" << [event deltaX] << [event deltaY];
     const NSTimeInterval timestamp = [event timestamp];
     QPointF windowPoint;
@@ -1290,6 +1346,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)beginGestureWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     const NSTimeInterval timestamp = [event timestamp];
     QPointF windowPoint;
     QPointF screenPoint;
@@ -1301,6 +1360,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 
 - (void)endGestureWithEvent:(NSEvent *)event
 {
+    if (m_platformWindow.isNull())
+        return;
+
     qCDebug(lcQpaGestures) << "endGestureWithEvent";
     const NSTimeInterval timestamp = [event timestamp];
     QPointF windowPoint;
@@ -1314,6 +1376,9 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
 #ifndef QT_NO_WHEELEVENT
 - (void)scrollWheel:(NSEvent *)theEvent
 {
+    if (m_platformWindow.isNull())
+        return;
+
     if ([self isTransparentForUserInput])
         return [super scrollWheel:theEvent];
 
@@ -1984,6 +2049,9 @@ static QPoint mapWindowCoordinates(QWindow *source, QWindow *target, QPoint poin
 // Sends drag update to Qt, return the action
 - (NSDragOperation)handleDrag:(id <NSDraggingInfo>)sender
 {
+    if (m_platformWindow.isNull())
+        return NSDragOperationNone;
+
     NSPoint windowPoint = [self convertPoint: [sender draggingLocation] fromView: nil];
     QPoint qt_windowPoint(windowPoint.x, windowPoint.y);
     Qt::DropActions qtAllowed = qt_mac_mapNSDragOperations([sender draggingSourceOperationMask]);
@@ -2011,6 +2079,9 @@ static QPoint mapWindowCoordinates(QWindow *source, QWindow *target, QPoint poin
 
 - (void)draggingExited:(id <NSDraggingInfo>)sender
 {
+    if (m_platformWindow.isNull())
+        return;
+
     QWindow *target = findEventTargetWindow(m_platformWindow->window());
     if (!target)
         return;
@@ -2025,6 +2096,9 @@ static QPoint mapWindowCoordinates(QWindow *source, QWindow *target, QPoint poin
 // called on drop, send the drop to Qt and return if it was accepted.
 - (BOOL)performDragOperation:(id <NSDraggingInfo>)sender
 {
+    if (m_platformWindow.isNull())
+        return false;
+
     QWindow *target = findEventTargetWindow(m_platformWindow->window());
     if (!target)
         return false;
@@ -2055,6 +2129,10 @@ static QPoint mapWindowCoordinates(QWindow *source, QWindow *target, QPoint poin
 {
     Q_UNUSED(session);
     Q_UNUSED(operation);
+
+    if (m_platformWindow.isNull())
+        return;
+
     QWindow *target = findEventTargetWindow(m_platformWindow->window());
     if (!target)
         return;

src/plugins/platforms/cocoa/qnsviewaccessibility.mm

@@ -53,6 +53,9 @@
 @implementation QNSView (QNSViewAccessibility)
 
 - (id)childAccessibleElement {
+    if (m_platformWindow.isNull())
+        return nil;
+
     if (!m_platformWindow->window()->accessibleRoot())
         return nil;