compositor: Add an API to query if the stage is focused

gnome-shell needs to know whether the stage window is focused so
it can synchronize between stage window focus and Clutter key actor
focus. Track all X windows, even those without MetaWindows, when
tracking the focus window, and add a compositor-level API to determine
when the stage is focused.

src/compositor/compositor.c

@@ -391,6 +391,24 @@ meta_focus_stage_window (MetaScreen *screen,
                                         timestamp);
 }
 
+gboolean
+meta_stage_is_focused (MetaScreen *screen)
+{
+  ClutterStage *stage;
+  Window window;
+
+  stage = CLUTTER_STAGE (meta_get_stage_for_screen (screen));
+  if (!stage)
+    return FALSE;
+
+  window = clutter_x11_get_stage_window (stage);
+
+  if (window == None)
+    return FALSE;
+
+  return (screen->display->focus_xwindow == window);
+}
+
 gboolean
 meta_begin_modal_for_plugin (MetaScreen       *screen,
                              MetaPlugin       *plugin,

src/core/display-private.h

@@ -113,6 +113,9 @@ struct _MetaDisplay
    * or event that caused this.
    */
   MetaWindow *focus_window;
+  /* For windows we've focused that don't necessarily have an X window,
+   * like the no_focus_window or the stage X window. */
+  Window focus_xwindow;
   gulong focus_serial;
 
   /* last timestamp passed to XSetInputFocus */

src/core/display.c

@@ -1876,11 +1876,12 @@ get_input_event (MetaDisplay *display,
 static void
 update_focus_window (MetaDisplay *display,
                      MetaWindow  *window,
+                     Window       xwindow,
                      gulong       serial)
 {
   display->focus_serial = serial;
 
-  if (window == display->focus_window)
+  if (display->focus_xwindow == xwindow)
     return;
 
   if (display->focus_window)
@@ -1897,11 +1898,13 @@ update_focus_window (MetaDisplay *display,
        */
       previous = display->focus_window;
       display->focus_window = NULL;
+      display->focus_xwindow = None;
 
       meta_window_set_focused_internal (previous, FALSE);
     }
 
   display->focus_window = window;
+  display->focus_xwindow = xwindow;
 
   if (display->focus_window)
     {
@@ -1952,6 +1955,7 @@ request_xserver_input_focus_change (MetaDisplay *display,
                                     guint32      timestamp)
 {
   MetaWindow *meta_window;
+  gulong serial;
 
   if (timestamp_too_old (display, &timestamp))
     return;
@@ -1959,14 +1963,40 @@ request_xserver_input_focus_change (MetaDisplay *display,
   meta_window = meta_display_lookup_x_window (display, xwindow);
 
   meta_error_trap_push (display);
-  update_focus_window (display,
-                       meta_window,
-                       XNextRequest (display->xdisplay));
+
+  /* In order for mutter to know that the focus request succeeded, we track
+   * the serial of the "focus request" we made, but if we take the serial
+   * of the XSetInputFocus request, then there's no way to determine the
+   * difference between focus events as a result of the SetInputFocus and
+   * focus events that other clients send around the same time. Ensure that
+   * we know which is which by making two requests that the server will
+   * process at the same time.
+   */
+  meta_display_grab (display);
 
   XSetInputFocus (display->xdisplay,
                   xwindow,
                   RevertToPointerRoot,
                   timestamp);
+
+  serial = XNextRequest (display->xdisplay);
+
+  {
+    unsigned long data[1] = { 0 };
+
+    XChangeProperty (display->xdisplay, display->timestamp_pinging_window,
+                     display->atom__MUTTER_FOCUS_SET,
+                     XA_CARDINAL,
+                     32, PropModeReplace, (guchar*) data, 1);
+  }
+
+  meta_display_ungrab (display);
+
+  update_focus_window (display,
+                       meta_window,
+                       xwindow,
+                       serial);
+
   meta_error_trap_pop (display);
 
   display->last_focus_time = timestamp;
@@ -2081,7 +2111,9 @@ handle_window_focus_event (MetaDisplay  *display,
 
   if (display->server_focus_serial >= display->focus_serial)
     {
-      update_focus_window (display, focus_window,
+      update_focus_window (display,
+                           focus_window,
+                           focus_window ? focus_window->xwindow : None,
                            display->server_focus_serial);
     }
 }
@@ -2137,6 +2169,7 @@ event_callback (XEvent   *event,
                   display->focus_window->desc);
       update_focus_window (display,
                            meta_display_lookup_x_window (display, display->server_focus_window),
+                           display->server_focus_window,
                            display->server_focus_serial);
     }
 

src/meta/atomnames.h

@@ -70,6 +70,7 @@ item(_GNOME_WM_KEYBINDINGS)
 item(_GNOME_PANEL_ACTION)
 item(_GNOME_PANEL_ACTION_MAIN_MENU)
 item(_GNOME_PANEL_ACTION_RUN_DIALOG)
+item(_MUTTER_FOCUS_SET)
 item(_MUTTER_SENTINEL)
 item(_MUTTER_VERSION)
 item(WM_CLIENT_MACHINE)

src/meta/compositor-mutter.h

@@ -48,5 +48,6 @@ void meta_set_stage_input_region     (MetaScreen    *screen,
 void meta_empty_stage_input_region   (MetaScreen    *screen);
 void meta_focus_stage_window         (MetaScreen    *screen,
                                       guint32        timestamp);
+gboolean meta_stage_is_focused       (MetaScreen    *screen);
 
 #endif