macOS: Don't call [NSOpenGLContext update] for every frame

Calling update has a cost, and should only be done when the drawable
object changes size or location. Instead of calling update each time
makeCurrent is called, we listen for the appropriate notifications,
limiting the number of update calls significantly.

We still call update on the thread owning the QOpenGLContext, which
is not ideal, as [NSOpenGLContext update] should only be called on
the main thread, but in practice this works. Getting out of this
situation is tricky, and setView has in theory the same problems.
Until those problems have been solved we keep the behavior as is.

Task-number: QTBUG-63572
Change-Id: Ibac9f8be7843f2aa006af6f7ee670bf027122440
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaglcontext.h b/src/plugins/platforms/cocoa/qcocoaglcontext.h
index cef5892989..eefb1cd0fb 100644
--- a/src/plugins/platforms/cocoa/qcocoaglcontext.h
+++ b/src/plugins/platforms/cocoa/qcocoaglcontext.h
@@ -41,6 +41,7 @@
 #define QCOCOAGLCONTEXT_H
 
 #include <QtCore/QPointer>
+#include <QtCore/private/qcore_mac_p.h>
 #include <qpa/qplatformopenglcontext.h>
 #include <QtGui/QOpenGLContext>
 #include <QtGui/QWindow>
@@ -79,6 +80,8 @@ private:
     NSOpenGLContext *m_shareContext = nil;
     QSurfaceFormat m_format;
     bool m_didCheckForSoftwareContext = false;
+    QVarLengthArray<QMacScopedObserver, 3> m_updateObservers;
+    QAtomicInt m_needsUpdate = false;
 };
 
 QT_END_NAMESPACE