macOS: Handle NSViewGlobalFrameDidChangeNotification via QCocoaWindow

The notification is only posted for NSViews with attached surfaces,
meaning NSOpenGLContext, so there's no need to guard the subscription
within [QNSView setQCocoaGLContext:].

Change-Id: I8179e58c84925a756315b711d15fa9c356adaecf
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

src/plugins/platforms/cocoa/qcocoawindow.h

@@ -198,6 +198,7 @@ public:
     Q_NOTIFICATION_HANDLER(NSWindowDidMoveNotification) void windowDidMove();
     Q_NOTIFICATION_HANDLER(NSWindowDidResizeNotification) void windowDidResize();
     Q_NOTIFICATION_HANDLER(NSViewFrameDidChangeNotification) void viewDidChangeFrame();
+    Q_NOTIFICATION_HANDLER(NSViewGlobalFrameDidChangeNotification) void viewDidChangeGlobalFrame();
     Q_NOTIFICATION_HANDLER(NSWindowDidEndLiveResizeNotification) void windowDidEndLiveResize();
     Q_NOTIFICATION_HANDLER(NSWindowDidBecomeKeyNotification) void windowDidBecomeKey();
     Q_NOTIFICATION_HANDLER(NSWindowDidResignKeyNotification) void windowDidResignKey();

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -1270,6 +1270,18 @@ void QCocoaWindow::viewDidChangeFrame()
     [qnsview_cast(m_view) updateGeometry];
 }
 
+/*!
+    Callback for NSViewGlobalFrameDidChangeNotification.
+
+    Posted whenever an NSView object that has attached surfaces (that is,
+    NSOpenGLContext objects) moves to a different screen, or other cases
+    where the NSOpenGLContext object needs to be updated.
+*/
+void QCocoaWindow::viewDidChangeGlobalFrame()
+{
+    updateExposedGeometry();
+}
+
 void QCocoaWindow::windowDidEndLiveResize()
 {
     if (m_synchedWindowState == Qt::WindowMaximized && ![m_nsWindow isZoomed]) {

src/plugins/platforms/cocoa/qnsview.h

@@ -74,7 +74,6 @@ Q_FORWARD_DECLARE_OBJC_CLASS(QT_MANGLE_NAMESPACE(QNSViewMouseMoveHelper));
     QStringList *currentCustomDragTypes;
     bool m_sendUpAsRightButton;
     Qt::KeyboardModifiers currentWheelModifiers;
-    bool m_subscribesForGlobalFrameNotifications;
 #ifndef QT_NO_OPENGL
     QCocoaGLContext *m_glContext;
     bool m_shouldSetGLContextinDrawRect;

src/plugins/platforms/cocoa/qnsview.mm

@@ -149,7 +149,6 @@ static bool _q_dontOverrideCtrlLMB = false;
         m_acceptedMouseDowns = Qt::NoButton;
         m_frameStrutButtons = Qt::NoButton;
         m_sendKeyEvent = false;
-        m_subscribesForGlobalFrameNotifications = false;
 #ifndef QT_NO_OPENGL
         m_glContext = 0;
         m_shouldSetGLContextinDrawRect = false;
@@ -181,7 +180,6 @@ static bool _q_dontOverrideCtrlLMB = false;
     CGImageRelease(m_maskImage);
     [m_trackingArea release];
     m_maskImage = 0;
-    m_subscribesForGlobalFrameNotifications = false;
     [m_inputSource release];
     [[NSNotificationCenter defaultCenter] removeObserver:self];
     [m_mouseMoveHelper release];
@@ -235,27 +233,9 @@ static bool _q_dontOverrideCtrlLMB = false;
         //was unable to set view
         m_shouldSetGLContextinDrawRect = true;
     }
-
-    if (!m_subscribesForGlobalFrameNotifications) {
-        // NSOpenGLContext expects us to repaint (or update) the view when
-        // it changes position on screen. Since this happens unnoticed for
-        // the view when the parent view moves, we need to register a special
-        // notification that lets us handle this case:
-        m_subscribesForGlobalFrameNotifications = true;
-        [[NSNotificationCenter defaultCenter] addObserver:self
-            selector:@selector(globalFrameChanged:)
-            name:NSViewGlobalFrameDidChangeNotification
-            object:self];
-    }
 }
 #endif
 
-- (void) globalFrameChanged:(NSNotification*)notification
-{
-    Q_UNUSED(notification);
-    m_platformWindow->updateExposedGeometry();
-}
-
 - (void)viewDidMoveToSuperview
 {
     if (!(m_platformWindow->m_viewIsToBeEmbedded))