[x11] Implement _GTK_SHOW_WINDOW_MENU.

BUG: 454756

src/netinfo.cpp

@@ -100,7 +100,8 @@ RootInfo *RootInfo::create()
         | NET::WM2FullscreenMonitors
         | NET::WM2KDEShadow
         | NET::WM2OpaqueRegion
-        | NET::WM2GTKFrameExtents;
+        | NET::WM2GTKFrameExtents
+        | NET::WM2GTKShowWindowMenu;
 #if KWIN_BUILD_ACTIVITIES
     properties2 |= NET::WM2Activities;
 #endif
@@ -216,6 +217,14 @@ void RootInfo::moveResizeWindow(xcb_window_t w, int flags, int x, int y, int wid
     }
 }
 
+void RootInfo::showWindowMenu(xcb_window_t w, int device_id, int x_root, int y_root)
+{
+    Q_UNUSED(device_id);
+    if (X11Window *c = Workspace::self()->findClient(Predicate::WindowMatch, w)) {
+        c->GTKShowWindowMenu(x_root, y_root);
+    }
+}
+
 void RootInfo::gotPing(xcb_window_t w, xcb_timestamp_t timestamp)
 {
     if (X11Window *c = Workspace::self()->findClient(Predicate::WindowMatch, w)) {

src/netinfo.h

@@ -42,6 +42,7 @@ protected:
     void closeWindow(xcb_window_t w) override;
     void moveResize(xcb_window_t w, int x_root, int y_root, unsigned long direction) override;
     void moveResizeWindow(xcb_window_t w, int flags, int x, int y, int width, int height) override;
+    void showWindowMenu(xcb_window_t w, int device_id, int x_root, int y_root) override;
     void gotPing(xcb_window_t w, xcb_timestamp_t timestamp) override;
     void restackWindow(xcb_window_t w, RequestSource source, xcb_window_t above, int detail, xcb_timestamp_t timestamp) override;
     void changeShowingDesktop(bool showing) override;

src/x11window.cpp

@@ -4077,6 +4077,13 @@ void X11Window::NETMoveResizeWindow(int flags, int x, int y, int width, int heig
     configureRequest(value_mask, x, y, width, height, gravity, true);
 }
 
+// _GTK_SHOW_WINDOW_MENU
+void X11Window::GTKShowWindowMenu(int x_root, int y_root)
+{
+    QPoint globalPos(x_root, y_root);
+    workspace()->showWindowMenu(QRect(globalPos, globalPos), this);
+}
+
 bool X11Window::isMovable() const
 {
     if (!hasNETSupport() && !m_motif.move()) {

src/x11window.h

@@ -236,6 +236,7 @@ public:
 
     void NETMoveResize(int x_root, int y_root, NET::Direction direction);
     void NETMoveResizeWindow(int flags, int x, int y, int width, int height);
+    void GTKShowWindowMenu(int x_root, int y_root);
     void restackWindow(xcb_window_t above, int detail, NET::RequestSource source, xcb_timestamp_t timestamp,
                        bool send_event = false);