[mutter/gbsneto/graphene-matrix] clutter/actor: Cache inverse transform

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit ff98fa99d1ec1672ee33e67bc765e8e8e3f07bdb
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Fri Sep 11 10:30:43 2020 -0300

    clutter/actor: Cache inverse transform
    
    It turns it to be quite easy to inverse the transform, and doing that
    on ClutterActor level means we can actually think about removing
    CoglMatrix entirely and using graphene_matrix_t everywhere.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1439

 clutter/clutter/clutter-actor.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/clutter/clutter/clutter-actor.c b/clutter/clutter/clutter-actor.c
index 68d32da6ca..52bf865a66 100644
--- a/clutter/clutter/clutter-actor.c
+++ b/clutter/clutter/clutter-actor.c
@@ -704,6 +704,7 @@ struct _ClutterActorPrivate
 
   /* the cached transformation matrix; see apply_transform() */
   CoglMatrix transform;
+  CoglMatrix inverse_transform;
 
   float resource_scale;
 
@@ -857,6 +858,7 @@ struct _ClutterActorPrivate
   guint had_effects_on_last_paint_volume_update : 1;
   guint absolute_origin_changed     : 1;
   guint needs_update_stage_views    : 1;
+  guint has_inverse_transform       : 1;
 };
 
 enum
@@ -1080,6 +1082,7 @@ static void clutter_actor_push_in_cloned_branch (ClutterActor *self,
                                                  gulong        count);
 static void clutter_actor_pop_in_cloned_branch (ClutterActor *self,
                                                 gulong        count);
+static void ensure_valid_actor_transform (ClutterActor *actor);
 
 static GQuark quark_actor_layout_info = 0;
 static GQuark quark_actor_transform_info = 0;
@@ -1253,17 +1256,21 @@ _clutter_actor_transform_local_box_to_stage (ClutterActor          *self,
                                              const ClutterActorBox *box,
                                              graphene_point_t       vertices[4])
 {
+  ClutterActor *stage_actor = CLUTTER_ACTOR (stage);
+  ClutterActorPrivate *stage_priv = stage_actor->priv;
   CoglFramebuffer *fb =
    clutter_pick_context_get_framebuffer (pick_context);
-  CoglMatrix stage_transform, inv_stage_transform;
   CoglMatrix modelview, transform_to_stage;
   int v;
 
-  clutter_actor_get_transform (CLUTTER_ACTOR (stage), &stage_transform);
-  if (!cogl_matrix_get_inverse (&stage_transform, &inv_stage_transform))
+   ensure_valid_actor_transform (stage_actor);
+
+  if (!stage_priv->has_inverse_transform)
     return FALSE;
   cogl_framebuffer_get_modelview_matrix (fb, &modelview);
-  cogl_matrix_multiply (&transform_to_stage, &inv_stage_transform, &modelview);
+  cogl_matrix_multiply (&transform_to_stage,
+                        &stage_priv->inverse_transform,
+                        &modelview);
 
   vertices[0].x = box->x1;
   vertices[0].y = box->y1;