macOS: Use QPointer to track QNSView -> QCocoaWindow

Change-Id: I4de581dda03d25e781112eff34de28dfd1797a7f
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -433,13 +433,6 @@ QCocoaWindow::~QCocoaWindow()
     if (window()->type() != Qt::ForeignWindow)
         [[NSNotificationCenter defaultCenter] removeObserver:m_view];
 
-    // The QNSView object may outlive the corresponding QCocoaWindow object,
-    // for example during app shutdown when the QNSView is embedded in a
-    // foregin NSView hiearchy. Clear the pointers to the QWindow/QCocoaWindow
-    // here to make sure QNSView does not dereference stale pointers.
-    if (window()->type() != Qt::ForeignWindow)
-        [qnsview_cast(m_view) clearQWindowPointers];
-
     // While it is unlikely that this window will be in the popup stack
     // during deletetion we clear any pointers here to make sure.
     if (QCocoaIntegration::instance()) {

src/plugins/platforms/cocoa/qnsview.h

@@ -65,7 +65,7 @@ Q_FORWARD_DECLARE_OBJC_CLASS(QT_MANGLE_NAMESPACE(QNSViewMouseMoveHelper));
     uchar *m_maskData;
     bool m_shouldInvalidateWindowShadow;
     QPointer<QWindow> m_window;
-    QCocoaWindow *m_platformWindow;
+    QPointer<QCocoaWindow> m_platformWindow;
     NSTrackingArea *m_trackingArea;
     Qt::MouseButtons m_buttons;
     Qt::MouseButtons m_acceptedMouseDowns;
@@ -92,7 +92,6 @@ Q_FORWARD_DECLARE_OBJC_CLASS(QT_MANGLE_NAMESPACE(QNSViewMouseMoveHelper));
 
 - (id)init;
 - (id)initWithQWindow:(QWindow *)window platformWindow:(QCocoaWindow *) platformWindow;
-- (void) clearQWindowPointers;
 #ifndef QT_NO_OPENGL
 - (void)setQCocoaGLContext:(QCocoaGLContext *)context;
 #endif

src/plugins/platforms/cocoa/qnsview.mm

@@ -229,12 +229,6 @@ static bool _q_dontOverrideCtrlLMB = false;
     return self;
 }
 
-- (void) clearQWindowPointers
-{
-    m_window = 0;
-    m_platformWindow = 0;
-}
-
 #ifndef QT_NO_OPENGL
 - (void) setQCocoaGLContext:(QCocoaGLContext *)context
 {