Add X11 composite window property in Application

This allows checking if the given override redirect is the composite
overlay window without resorting to platform specific implementation of
Compositor.

src/compositor_x11.cpp

@@ -149,6 +149,7 @@ void X11Compositor::start()
         // Internal setup failed, abort.
         return;
     }
+    kwinApp()->setX11CompositeWindow(backend()->overlayWindow()->window());
     startupWithWorkspace();
     m_syncManager.reset(X11SyncManager::create());
 }
@@ -157,6 +158,7 @@ void X11Compositor::stop()
 {
     m_syncManager.reset();
     Compositor::stop();
+    kwinApp()->setX11CompositeWindow(XCB_WINDOW_NONE);
 }
 
 void X11Compositor::composite(RenderLoop *renderLoop)
@@ -215,20 +217,6 @@ void X11Compositor::composite(RenderLoop *renderLoop)
     }
 }
 
-bool X11Compositor::checkForOverlayWindow(WId w) const
-{
-    if (!backend()) {
-        // No backend, so it cannot be the overlay window.
-        return false;
-    }
-    if (!backend()->overlayWindow()) {
-        // No overlay window, it cannot be the overlay.
-        return false;
-    }
-    // Compare the window ID's.
-    return w == backend()->overlayWindow()->window();
-}
-
 bool X11Compositor::isOverlayWindowVisible() const
 {
     if (!backend()) {

src/compositor_x11.h

@@ -80,11 +80,6 @@ public:
     bool openGLCompositingIsBroken() const override;
     void createOpenGLSafePoint(OpenGLSafePoint safePoint) override;
 
-    /**
-     * Checks whether @p w is the Scene's overlay window.
-     */
-    bool checkForOverlayWindow(WId w) const;
-
     /**
      * @returns Whether the Scene's Overlay X Window is visible.
      */

src/main.h

@@ -181,6 +181,14 @@ public:
         return m_rootWindow;
     }
 
+    /**
+     * @returns the X11 composite overlay window handle.
+     */
+    xcb_window_t x11CompositeWindow() const
+    {
+        return m_compositeWindow;
+    }
+
     /**
      * @returns the X11 xcb connection
      */
@@ -205,6 +213,10 @@ public:
     {
         m_connection = c;
     }
+    void setX11CompositeWindow(xcb_window_t window)
+    {
+        m_compositeWindow = window;
+    }
 
     qreal xwaylandScale() const
     {
@@ -368,6 +380,7 @@ private:
     OperationMode m_operationMode;
     xcb_timestamp_t m_x11Time = XCB_TIME_CURRENT_TIME;
     xcb_window_t m_rootWindow = XCB_WINDOW_NONE;
+    xcb_window_t m_compositeWindow = XCB_WINDOW_NONE;
     xcb_connection_t *m_connection = nullptr;
 #if KWIN_BUILD_ACTIVITIES
     bool m_useKActivities = true;

src/workspace.cpp

@@ -661,10 +661,8 @@ X11Window *Workspace::createX11Window(xcb_window_t windowId, bool is_mapped)
 
 X11Window *Workspace::createUnmanaged(xcb_window_t windowId)
 {
-    if (X11Compositor *compositor = X11Compositor::self()) {
-        if (compositor->checkForOverlayWindow(windowId)) {
-            return nullptr;
-        }
+    if (kwinApp()->x11CompositeWindow() == windowId) {
+        return nullptr;
     }
     X11Window *window = new X11Window();
     if (!window->track(windowId)) {