1 files changed, 12 insertions, 9 deletions
diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index 824603be98..93b7169237 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -1226,15 +1226,18 @@ void QCocoaWindow::windowDidResignKey()
     if (isForeignWindow())
         return;
 
-    // Key window will be non-nil if another window became key, so do not
-    // set the active window to zero here -- the new key window's
-    // NSWindowDidBecomeKeyNotification hander will change the active window.
-    NSWindow *keyWindow = [NSApp keyWindow];
-    if (!keyWindow || keyWindow == m_view.window) {
-        // No new key window, go ahead and set the active window to zero
-        if (!windowIsPopupType())
-            QWindowSystemInterface::handleWindowActivated<QWindowSystemInterface::SynchronousDelivery>(
-                nullptr, Qt::ActiveWindowFocusReason);
+    // The current key window will be non-nil if another window became key. If that
+    // window is a Qt window, we delay the window activation event until the didBecomeKey
+    // notification is delivered to the active window, to ensure an atomic update.
+    NSWindow *newKeyWindow = [NSApp keyWindow];
+    if (newKeyWindow && newKeyWindow != m_view.window
+        && [newKeyWindow conformsToProtocol:@protocol(QNSWindowProtocol)])
+        return;
+
+    // Lost key window, go ahead and set the active window to zero
+    if (!windowIsPopupType()) {
+        QWindowSystemInterface::handleWindowActivated<QWindowSystemInterface::SynchronousDelivery>(
+            nullptr, Qt::ActiveWindowFocusReason);
     }
 }