Merge remote-tracking branch 'origin/5.11' into dev

 Conflicts:
	src/plugins/platforms/cocoa/qcocoabackingstore.mm
	src/plugins/platforms/cocoa/qcocoascreen.mm

Change-Id: Iac965aea4867059dbf7bc401b71e8e8b5b259afb

1 files changed, 5 insertions, 5 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.mm b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
index 332683f63e..13b4e2ecd1 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.mm
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
@@ -159,13 +159,13 @@ void QCocoaBackingStore::flush(QWindow *window, const QRegion &region, const QPo
 
         const qreal devicePixelRatio = m_image.devicePixelRatio();
 
-        // If the flushed window is a content view, and not in unified toolbar mode,
-        // and is fully opaque, we can get away with copying the backingstore instead
-        // of blending.
+        // If the flushed window is a content view, and we're filling the drawn area
+        // completely, or it doesn't have a window background we need to preserve,
+        // we can get away with copying instead of blending the backing store.
         QCocoaWindow *cocoaWindow = static_cast<QCocoaWindow *>(window->handle());
         const NSCompositingOperation compositingOperation = cocoaWindow->isContentView()
-                && cocoaWindow->isOpaque() && !windowHasUnifiedToolbar() ?
-                NSCompositingOperationCopy : NSCompositingOperationSourceOver;
+            && (cocoaWindow->isOpaque() || view.window.backgroundColor == NSColor.clearColor)
+                ? NSCompositingOperationCopy : NSCompositingOperationSourceOver;
 
 #ifdef QT_DEBUG
         static bool debugBackingStoreFlush = [[NSUserDefaults standardUserDefaults]