macOS: Send expose event at drawRect and trigger updates via setNeedsDisplay

This changes the drawing model on macOS from the following:

 1. Sending synchronous expose events directly from callbacks such as
    windowDidOrderOnScreen and windowDidChangeOcclusionState
 2. Waiting for a resulting flush of the backing store, and issuing
    setNeedsDisplay as a response
 3. Waiting for the asynchronous drawRect call in response to
    setNeedsDisplay, where the backing store is finally drawn
    to the window

To the following:

 1. Issue setNeedsDisplay as a response to callbacks such as
    windowDidOrderOnScreen and windowDidChangeOcclusionState,
    when needed (in many cases this is automatic by AppKit)
 2. Send synchronous expose events from the resulting drawRect
    callback
 3. Draw the backing store to the window when flushed

The new model matches how normal Cocoa application draw in response to
drawRect, and makes the backing store flush synchronous instead of having
to trigger a async setNeedsDisplay. This gives AppKit more information
about how much time we're spending in drawRect, as the actual drawing
and flushing all happens within the synchronous expose event.

Qt applications that draw outside of drawRect, e.g. in response to timers,
are still supported by manually locking focus of the view and flushing the
window at the end of the backingstore flush.

Task-number: QTBUG-50414
Change-Id: I2efb9ff8df51ab6e840ad20c497b71f53e21e1c2
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 1 insertions, 7 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoawindow.h b/src/plugins/platforms/cocoa/qcocoawindow.h
index e2fb372dae..e20f033a43 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.h
+++ b/src/plugins/platforms/cocoa/qcocoawindow.h
@@ -188,10 +188,6 @@ public:
     void updateNSToolbar();
 
     qreal devicePixelRatio() const Q_DECL_OVERRIDE;
-    bool isWindowExposable();
-    void exposeWindow();
-    void obscureWindow();
-    void updateExposedGeometry();
     QWindow *childWindowAt(QPoint windowPoint);
     bool shouldRefuseKeyWindowAndFirstResponder();
 
@@ -238,6 +234,7 @@ public: // for QNSView
 
     void handleGeometryChange();
     void handleWindowStateChanged(HandleFlags flags = NoHandleFlags);
+    void handleExposeEvent(const QRegion &region);
 
     NSView *m_view;
     QCocoaNSWindow *m_nsWindow;
@@ -264,10 +261,7 @@ public: // for QNSView
 
     bool m_hasModalSession;
     bool m_frameStrutEventsEnabled;
-    bool m_geometryUpdateExposeAllowed;
     bool m_isExposed;
-    QRect m_exposedGeometry;
-    qreal m_exposedDevicePixelRatio;
     int m_registerTouchCount;
     bool m_resizableTransientParent;