macOS: Determine opaqueness and backgroundColor of NSWindow declaratively

Instead of imperatively trying to keep the logic consistent in many
different call sites.

Task-number: QTBUG-61909
Change-Id: I8d647690c47656f34673555a8a8aa3ec6ffc73d1
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/plugins/platforms/cocoa/qnswindow.mm b/src/plugins/platforms/cocoa/qnswindow.mm
index e5ddd3ca0f..513c7f22b5 100644
--- a/src/plugins/platforms/cocoa/qnswindow.mm
+++ b/src/plugins/platforms/cocoa/qnswindow.mm
@@ -153,6 +153,28 @@ static bool isMouseEvent(NSEvent *ev)
     return canBecomeMain;
 }
 
+- (BOOL)isOpaque
+{
+    return self.platformWindow ?
+        self.platformWindow->isOpaque() : qt_objcDynamicSuper();
+}
+
+/*!
+    Borderless windows need a transparent background
+
+    Technically windows with NSTexturedBackgroundWindowMask (such
+    as windows with unified toolbars) need to draw the textured
+    background of the NSWindow, and can't have a transparent
+    background, but as NSBorderlessWindowMask is 0, you can't
+    have a window with NSTexturedBackgroundWindowMask that is
+    also borderless.
+*/
+- (NSColor *)backgroundColor
+{
+    return self.styleMask == NSBorderlessWindowMask
+        ? [NSColor clearColor] : qt_objcDynamicSuper();
+}
+
 - (void)sendEvent:(NSEvent*)theEvent
 {
     // We might get events for a NSWindow after the corresponding platform