window-actor: Remove the bounding region

With the shape region always set, it turns out the bounding region
is only used in one place, that's easily replaced with a variable
we already have available to us.

https://bugzilla.gnome.org/show_bug.cgi?id=679901

src/compositor/meta-window-actor.c

@@ -70,8 +70,6 @@ struct _MetaWindowActorPrivate
 
   /* A region that matches the shape of the window, including frame bounds */
   cairo_region_t   *shape_region;
-  /* A rectangular region with the visible extents of the window */
-  cairo_region_t   *bounding_region;
   /* The region we should clip to when painting the shadow */
   cairo_region_t   *shadow_clip;
 
@@ -80,7 +78,6 @@ struct _MetaWindowActorPrivate
 
   gint              last_width;
   gint              last_height;
-  MetaFrameBorders  last_borders;
 
   gint              freeze_count;
 
@@ -390,7 +387,6 @@ meta_window_actor_dispose (GObject *object)
   meta_window_actor_detach (self);
 
   g_clear_pointer (&priv->shape_region, cairo_region_destroy);
-  g_clear_pointer (&priv->bounding_region, cairo_region_destroy);
   g_clear_pointer (&priv->shadow_clip, cairo_region_destroy);
 
   g_clear_pointer (&priv->shadow_class, g_free);
@@ -1303,6 +1299,7 @@ meta_window_actor_sync_actor_position (MetaWindowActor *self)
     {
       priv->size_changed = TRUE;
       meta_window_actor_queue_create_pixmap (self);
+      meta_window_actor_update_shape (self);
 
       priv->last_width = window_rect.width;
       priv->last_height = window_rect.height;
@@ -1539,55 +1536,6 @@ meta_window_actor_unmapped (MetaWindowActor *self)
   priv->needs_pixmap = FALSE;
 }
 
-static void
-meta_window_actor_update_bounding_region_and_borders (MetaWindowActor *self,
-                                                      int              width,
-                                                      int              height)
-{
-  MetaWindowActorPrivate *priv = self->priv;
-  MetaFrameBorders borders;
-  cairo_rectangle_int_t bounding_rectangle;
-
-  meta_frame_calc_borders (priv->window->frame, &borders);
-
-  bounding_rectangle.x = borders.invisible.left;
-  bounding_rectangle.y = borders.invisible.top;
-
-  width -= borders.invisible.left + borders.invisible.right;
-  height -= borders.invisible.top + borders.invisible.bottom;
-
-  bounding_rectangle.width = width;
-  bounding_rectangle.height = height;
-
-  if (priv->bounding_region != NULL)
-    {
-      cairo_rectangle_int_t old_bounding_rectangle;
-      cairo_region_get_extents (priv->bounding_region, &old_bounding_rectangle);
-
-      /* Because the bounding region doesn't include the invisible borders,
-       * we need to make sure that the border sizes haven't changed before
-       * short-circuiting early.
-       */
-      if (bounding_rectangle.width == old_bounding_rectangle.width &&
-          bounding_rectangle.height == old_bounding_rectangle.height &&
-          priv->last_borders.invisible.left == borders.invisible.left &&
-          priv->last_borders.invisible.right == borders.invisible.right &&
-          priv->last_borders.invisible.top == borders.invisible.top &&
-          priv->last_borders.invisible.bottom == borders.invisible.bottom)
-        return;
-    }
-
-  priv->last_borders = borders;
-
-  g_clear_pointer (&priv->bounding_region, cairo_region_destroy);
-
-  priv->bounding_region = cairo_region_create_rectangle (&bounding_rectangle);
-
-  meta_window_actor_update_shape (self);
-
-  g_signal_emit (self, signals[SIZE_CHANGED], 0);
-}
-
 /**
  * meta_window_actor_get_obscured_region:
  * @self: a #MetaWindowActor
@@ -1773,7 +1721,6 @@ check_needs_pixmap (MetaWindowActor *self)
       if (priv->back_pixmap == None)
         {
           meta_verbose ("Unable to get named pixmap for %p\n", self);
-          meta_window_actor_update_bounding_region_and_borders (self, 0, 0);
           goto out;
         }
 
@@ -1794,9 +1741,16 @@ check_needs_pixmap (MetaWindowActor *self)
       if (G_UNLIKELY (!cogl_texture_pixmap_x11_is_using_tfp_extension (texture)))
         g_warning ("NOTE: Not using GLX TFP!\n");
 
-      meta_window_actor_update_bounding_region_and_borders (self,
+      /* ::size-changed is supposed to refer to meta_window_get_outer_rect().
-                                                            cogl_texture_get_width (texture),
+       * Emitting it here works pretty much OK because a new value of the
-                                                            cogl_texture_get_height (texture));
+       * *input* rect (which is the outer rect with the addition of invisible
+       * borders) forces a new pixmap and we get here. In the rare case where
+       * a change to the window size was exactly balanced by a change to the
+       * invisible borders, we would miss emitting the signal. We would also
+       * emit spurious signals when we get a new pixmap without a new size,
+       * but that should be mostly harmless.
+       */
+      g_signal_emit (self, signals[SIZE_CHANGED], 0);
     }
 
   priv->needs_pixmap = FALSE;
@@ -2206,7 +2160,18 @@ check_needs_reshape (MetaWindowActor *self)
 
   needs_mask = (region != NULL) || (priv->window->frame != NULL);
 
-  if (region == NULL)
+  if (region != NULL)
+    {
+      /* The shape we get back from the client may have coordinates
+       * outside of the frame. The X SHAPE Extension requires that
+       * the overall shape the client provides never exceeds the
+       * "bounding rectangle" of the window -- the shape that the
+       * window would have gotten if it was unshaped. In our case,
+       * this is simply the client area.
+       */
+      cairo_region_intersect_rectangle (region, &client_area);
+    }
+  else
     {
       /* If we don't have a shape on the server, that means that
        * we have an implicit shape of one rectangle covering the
@@ -2214,6 +2179,9 @@ check_needs_reshape (MetaWindowActor *self)
       region = cairo_region_create_rectangle (&client_area);
     }
 
+  /* The region at this point should be constrained to the
+   * bounds of the client rectangle. */
+
   if (needs_mask)
     {
       /* This takes the region, generates a mask using GTK+
@@ -2225,20 +2193,6 @@ check_needs_reshape (MetaWindowActor *self)
 
   priv->shape_region = region;
 
-  /* Our "shape_region" is called the "bounding region" in the X Shape
-   * Extension Documentation.
-   *
-   * Our "bounding_region" is called the "bounding rectangle", which defines
-   * the shape of the window as if it the window was unshaped.
-   *
-   * The X Shape extension requires that the "bounding region" can never
-   * extend outside the "bounding rectangle", and says it must be implicitly
-   * clipped before rendering. The region we get back hasn't been clipped.
-   * We explicitly clip the region here.
-   */
-  if (priv->bounding_region != NULL)
-    cairo_region_intersect (priv->shape_region, priv->bounding_region);
-
   priv->needs_reshape = FALSE;
   meta_window_actor_invalidate_shadow (self);
 }