Move traffic lights logic into one place.

native/Avalonia.Native/src/OSX/AvnWindow.mm

@@ -274,10 +274,6 @@
 -(void) setEnabled:(bool)enable
 {
     _isEnabled = enable;
-    
-    [[self standardWindowButton:NSWindowCloseButton] setEnabled:enable];
-    [[self standardWindowButton:NSWindowMiniaturizeButton] setEnabled:enable];
-    [[self standardWindowButton:NSWindowZoomButton] setEnabled:enable];
 }
 
 -(void)becomeKeyWindow

native/Avalonia.Native/src/OSX/WindowImpl.mm

@@ -599,9 +599,14 @@ void WindowImpl::UpdateStyle() {
     bool wantsChrome = (_extendClientHints & AvnSystemChrome) || (_extendClientHints & AvnPreferSystemChrome);
     bool hasTrafficLights = _isClientAreaExtended ? wantsChrome : _decorations == SystemDecorationsFull;
     
-    [[Window standardWindowButton:NSWindowCloseButton] setHidden:!hasTrafficLights];
+    NSButton* closeButton = [Window standardWindowButton:NSWindowCloseButton];
-    [[Window standardWindowButton:NSWindowMiniaturizeButton] setHidden:!hasTrafficLights];
+    NSButton* miniaturizeButton = [Window standardWindowButton:NSWindowMiniaturizeButton];
-    [[Window standardWindowButton:NSWindowZoomButton] setHidden:!hasTrafficLights];
+    NSButton* zoomButton = [Window standardWindowButton:NSWindowZoomButton];
-    [[Window standardWindowButton:NSWindowZoomButton] setEnabled:_canResize];
-}
 
+    [closeButton setHidden:!hasTrafficLights];
+    [closeButton setEnabled:_isEnabled];
+    [miniaturizeButton setHidden:!hasTrafficLights];
+    [miniaturizeButton setEnabled:_isEnabled];
+    [zoomButton setHidden:!hasTrafficLights];
+    [zoomButton setEnabled:_isEnabled && _canResize];
+}