clutter/actor: Add get_transformed_extents

The clutter_actor_get_transformed_position returns the position of the
top left point of the actor, with the actor transformations. That means
that if the actor is rotated 180º it'll return the "screen" position top
right.

Using this to calculate if the actor is in the screen is causing
problems when it's transformted.

This patch adds a new function clutter_actor_get_transformed_extents,
that will return the transformed actor bounding rect.

This new function is used on the update_stage_views so the actor will
get updated. this way rotated actors will be updated if they are on the
screen.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1386

clutter/clutter/clutter-actor.c

@@ -10295,6 +10295,38 @@ clutter_actor_get_fixed_position (ClutterActor *self,
   return FALSE;
 }
 
+/**
+ * clutter_actor_get_transformed_extents:
+ * @self: A #ClutterActor
+ * @rect: (out): return location for the transformed bounding rect
+ *
+ * Gets the transformed bounding rect of an actor, in pixels relative to the stage.
+ */
+void
+clutter_actor_get_transformed_extents (ClutterActor    *self,
+                                       graphene_rect_t *rect)
+{
+  graphene_quad_t quad;
+  graphene_point3d_t v[4];
+  ClutterActorBox box;
+
+  box.x1 = 0;
+  box.y1 = 0;
+  box.x2 = clutter_actor_box_get_width (&self->priv->allocation);
+  box.y2 = clutter_actor_box_get_height (&self->priv->allocation);
+  if (_clutter_actor_transform_and_project_box (self, &box, v))
+    {
+      graphene_quad_init (&quad,
+                          (graphene_point_t *) &v[0],
+                          (graphene_point_t *) &v[1],
+                          (graphene_point_t *) &v[2],
+                          (graphene_point_t *) &v[3]);
+
+      if (rect)
+        graphene_quad_bounds (&quad, rect);
+    }
+}
+
 /**
  * clutter_actor_get_transformed_position:
  * @self: A #ClutterActor
@@ -16183,12 +16215,7 @@ update_stage_views (ClutterActor *self)
   stage = CLUTTER_STAGE (_clutter_actor_get_stage_internal (self));
   g_return_if_fail (stage);
 
-  clutter_actor_get_transformed_position (self,
+  clutter_actor_get_transformed_extents (self, &bounding_rect);
-                                          &bounding_rect.origin.x,
-                                          &bounding_rect.origin.y);
-  clutter_actor_get_transformed_size (self,
-                                      &bounding_rect.size.width,
-                                      &bounding_rect.size.height);
 
   if (bounding_rect.size.width == 0.0 ||
       bounding_rect.size.height == 0.0)

clutter/clutter/clutter-actor.h

@@ -813,6 +813,11 @@ void                            clutter_actor_set_child_transform
 CLUTTER_EXPORT
 void                            clutter_actor_get_child_transform               (ClutterActor               *self,
                                                                                  ClutterMatrix              *transform);
+
+CLUTTER_EXPORT
+void                            clutter_actor_get_transformed_extents          (ClutterActor               *self,
+                                                                                graphene_rect_t            *rect);
+
 CLUTTER_EXPORT
 void                            clutter_actor_get_transformed_position          (ClutterActor               *self,
                                                                                  gfloat                     *x,