window: Add get_client_content_rect

In acbb14f34bc8fee14e77db3c100e5d116d8e3d60, we have dropped the
is_client_decorated except it was still being used by gnome-shell
to adjust the window coordinates in case it is using server side
decoration.

Instead of re-adding the same function, expose a new function that
takes care of getting the whole client area while taking into account
SSD for X11 clients.

Helps https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7984

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4087>

src/core/window.c

@@ -8177,3 +8177,24 @@ meta_window_protocol_to_stage_point (MetaWindow          *window,
                             stage_x, stage_y,
                             rounding_strategy);
 }
+
+/**
+ * meta_window_get_client_content_rect:
+ * @window: A #MetaWindow
+ * @rect: (out): pointer to an allocated #MtkRectangle
+ *
+ * Gets the client rectangle that ATSPI window coordinates
+ * are relative to.
+ */
+void
+meta_window_get_client_content_rect (MetaWindow   *window,
+                                     MtkRectangle *rect)
+{
+  meta_window_get_frame_rect (window, rect);
+
+#ifdef HAVE_X11_CLIENT
+  if (window->client_type == META_WINDOW_CLIENT_TYPE_X11 &&
+      meta_window_x11_is_ssd (window))
+    meta_window_frame_rect_to_client_rect (window, rect, rect);
+#endif
+}

src/meta/window.h

@@ -123,6 +123,10 @@ META_EXPORT
 void meta_window_get_frame_rect (const MetaWindow *window,
                                 MtkRectangle      *rect);
 
+META_EXPORT
+void meta_window_get_client_content_rect (MetaWindow   *window,
+                                          MtkRectangle *rect);
+
 META_EXPORT
 void meta_window_client_rect_to_frame_rect (MetaWindow   *window,
                                             MtkRectangle *client_rect,