workspace: Only consider windows that should be showing as focusable

When selecting the default focus window, is_focusable() was not
considering the new conditions for whether a window should be shown or
hidden that were added to meta_window_should_be_showing() in 39942974.
As a result the default focus window could end up a window already
hidden or hidden once meta_window_flush_calc_showing() is called by
meta_window_focus() when focusing the default window. This would cause
meta_window_focus() to fail, which is an issue if it prevents us from
unfocusing a window when it is getting unmanaged.

Fixes: 399429742 ("x11: Integrate frames client into Mutter")
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2644
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2962>

src/core/window-private.h

@@ -669,6 +669,9 @@ void        meta_window_resize_frame_with_gravity (MetaWindow  *window,
                                                    int          h,
                                                    MetaGravity  gravity);
 
+gboolean    meta_window_should_be_showing_on_workspace (MetaWindow    *window,
+                                                        MetaWorkspace *workspace);
+
 /* Return whether the window should be currently mapped */
 gboolean    meta_window_should_be_showing   (MetaWindow  *window);
 

src/core/window.c

@@ -1691,10 +1691,9 @@ meta_window_showing_on_its_workspace (MetaWindow *window)
 }
 
 gboolean
-meta_window_should_be_showing (MetaWindow  *window)
+meta_window_should_be_showing_on_workspace (MetaWindow    *window,
+                                            MetaWorkspace *workspace)
 {
-  MetaWorkspaceManager *workspace_manager = window->display->workspace_manager;
-
 #ifdef HAVE_WAYLAND
   if (window->client_type == META_WINDOW_CLIENT_TYPE_WAYLAND)
     {
@@ -1709,11 +1708,20 @@ meta_window_should_be_showing (MetaWindow  *window)
     return FALSE;
 
   /* Windows should be showing if they're located on the
-   * active workspace and they're showing on their own workspace. */
-  return (meta_window_located_on_workspace (window, workspace_manager->active_workspace) &&
+   * workspace and they're showing on their own workspace. */
+  return (meta_window_located_on_workspace (window, workspace) &&
           meta_window_showing_on_its_workspace (window));
 }
 
+gboolean
+meta_window_should_be_showing (MetaWindow *window)
+{
+  MetaWorkspaceManager *workspace_manager = window->display->workspace_manager;
+  MetaWorkspace *active_workspace = workspace_manager->active_workspace;
+
+  return meta_window_should_be_showing_on_workspace (window, active_workspace);
+}
+
 static void
 implement_showing (MetaWindow *window,
                    gboolean    showing)

src/core/workspace.c

@@ -1436,8 +1436,7 @@ is_focusable (MetaWindow    *window,
          window->unmaps_pending == 0 &&
          window->type != META_WINDOW_DOCK &&
          meta_window_is_focusable (window) &&
-         meta_window_located_on_workspace (window, workspace) &&
-         meta_window_showing_on_its_workspace (window);
+         meta_window_should_be_showing_on_workspace (window, workspace);
 }
 
 static gboolean