waylandsink: Ensure correct mapping of area_surface

If the `area_surface` got unmapped when changing to the `READY` or
`NULL` state, we currently don't remap it when playback resumes and
`wp_viewporter` is supported. Without `wp_viewporter` we do remap
it, but rather unintentionally and also when not wanted.

On Weston this has not been a big problem as it so far wrongly maps
subsurfaces of unmapped surfaces anyway - i.e. only the black
background was missing on resume. On other compositors and future
Weston this prevents the `video_surface` to get remapped.

Shuffle things around to ensure `area_surface` is mapped in the
right situations and do some minor cleanup.

See also https://gitlab.freedesktop.org/wayland/weston/-/issues/426

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1483>

subprojects/gst-plugins-bad/ext/wayland/wlwindow.c

@@ -43,6 +43,8 @@ G_DEFINE_TYPE (GstWlWindow, gst_wl_window, G_TYPE_OBJECT);
 
 static void gst_wl_window_finalize (GObject * gobject);
 
+static void gst_wl_window_update_borders (GstWlWindow * window);
+
 static void
 handle_xdg_toplevel_close (void *data, struct xdg_toplevel *xdg_toplevel)
 {
@@ -454,12 +456,19 @@ gst_wl_window_render (GstWlWindow * window, GstWlBuffer * buffer,
     wl_surface_damage_buffer (window->video_surface_wrapper, 0, 0, G_MAXINT32,
         G_MAXINT32);
     wl_surface_commit (window->video_surface_wrapper);
+
+    if (!window->is_area_surface_mapped) {
+      gst_wl_window_update_borders (window);
+      wl_surface_commit (window->area_surface_wrapper);
+      window->is_area_surface_mapped = TRUE;
+    }
   } else {
     /* clear both video and parent surfaces */
     wl_surface_attach (window->video_surface_wrapper, NULL, 0, 0);
     wl_surface_commit (window->video_surface_wrapper);
     wl_surface_attach (window->area_surface_wrapper, NULL, 0, 0);
     wl_surface_commit (window->area_surface_wrapper);
+    window->is_area_surface_mapped = FALSE;
   }
 
   if (G_UNLIKELY (info)) {
@@ -486,12 +495,19 @@ gst_wl_window_update_borders (GstWlWindow * window)
   GstWlBuffer *gwlbuf;
   GstAllocator *alloc;
 
-  if (window->no_border_update)
+  if (window->display->viewporter) {
-    return;
+    wp_viewport_set_destination (window->area_viewport,
+        window->render_rectangle.w, window->render_rectangle.h);
+
+    if (window->is_area_surface_mapped) {
+      /* The area_surface is already visible and only needed to get resized.
+       * We don't need to attach a new buffer and are done here. */
+      return;
+    }
+  }
 
   if (window->display->viewporter) {
     width = height = 1;
-    window->no_border_update = TRUE;
   } else {
     width = window->render_rectangle.w;
     height = window->render_rectangle.h;
@@ -527,6 +543,10 @@ gst_wl_window_set_render_rectangle (GstWlWindow * window, gint x, gint y,
 {
   g_return_if_fail (window != NULL);
 
+  if (window->render_rectangle.x == x && window->render_rectangle.y == y &&
+      window->render_rectangle.w == w && window->render_rectangle.h == h)
+    return;
+
   window->render_rectangle.x = x;
   window->render_rectangle.y = y;
   window->render_rectangle.w = w;
@@ -536,11 +556,8 @@ gst_wl_window_set_render_rectangle (GstWlWindow * window, gint x, gint y,
   if (window->area_subsurface)
     wl_subsurface_set_position (window->area_subsurface, x, y);
 
-  /* change the size of the area */
+  if (window->is_area_surface_mapped)
-  if (window->area_viewport)
+    gst_wl_window_update_borders (window);
-    wp_viewport_set_destination (window->area_viewport, w, h);
-
-  gst_wl_window_update_borders (window);
 
   if (!window->configured)
     return;

subprojects/gst-plugins-bad/ext/wayland/wlwindow.h

@@ -68,10 +68,9 @@ struct _GstWlWindow
   /* the size of the video in the buffers */
   gint video_width, video_height;
 
-  /* this will be set when viewporter is available and black background has
+  /* when this is not set both the area_surface and the video_surface are not
-   * already been set on the area_subsurface */
+   * visible and certain steps should be skipped */
-  gboolean no_border_update;
+  gboolean is_area_surface_mapped;
-
 };
 
 struct _GstWlWindowClass