picking: Fix tracking of pick buffer validity

We have an optimization to track when there are multiple picks per
frame so we can do a full render of the pick buffer to reduce the
number of pick renders for a static scene.

There was a problem though in that we were tracking this information in
the ClutterMainContext, but conceptually this doesn't really make sense
because the pick buffer is associated with a stage framebuffer and there
can be multiple stages for one context.

This patch moves the state tracking to ClutterStage.

clutter/clutter-actor.c

@@ -1780,7 +1780,7 @@ clutter_actor_real_queue_redraw (ClutterActor *self,
                                  ClutterActor *origin)
 {
   ClutterActor *parent;
-  ClutterMainContext *context;
+  ClutterActor *stage;
 
   CLUTTER_NOTE (PAINT, "Redraw queued on '%s' (from: '%s')",
                 get_actor_debug_name (self),
@@ -1798,16 +1798,11 @@ clutter_actor_real_queue_redraw (ClutterActor *self,
   if (!CLUTTER_ACTOR_IS_VISIBLE (self))
     return;
 
-  /* We have an optimization in _clutter_do_pick to detect when the scene is
-   * static so we can cache a full, un-clipped pick buffer to avoid continuous
-   * pick renders.
-   *
-   * Currently the assumption is that actors queue a redraw when some state
-   * changes that affects painting *or* picking so we can use this point
-   * to invalidate any currently cached pick buffer.
+  /* XXX: when we merge the paint-box branch we should only need to
+   * invalidate the pick buffer in _clutter_stage_queue_actor_redraw
    */
-  context = _clutter_context_get_default ();
-  context->have_complete_pick_buffer = FALSE;
+  stage = _clutter_actor_get_stage_internal (self);
+  _clutter_stage_set_pick_buffer_valid (CLUTTER_STAGE (stage), FALSE);
 
   /* Although we could determine here that a full stage redraw
    * has already been queued and immediately bail out, we actually
@@ -1818,8 +1813,6 @@ clutter_actor_real_queue_redraw (ClutterActor *self,
    */
   if (self->priv->propagated_one_redraw)
     {
-      ClutterActor *stage = _clutter_actor_get_stage_internal (self);
-
       if (stage != NULL &&
           _clutter_stage_has_full_redraw_queued (CLUTTER_STAGE (stage)))
         return;

clutter/clutter-main.c

@@ -274,12 +274,8 @@ _clutter_do_redraw (ClutterStage *stage)
 
   ctx = _clutter_context_get_default ();
 
-  /* We have an optimization to avoid pick renders while scene is static.
-   * This is implied by seeing multiple picks per frame so we have to
-   * reset a pick counter each frame and also invalidate any current pick
-   * buffer. */
-  ctx->picks_per_frame = 0;
-  ctx->have_complete_pick_buffer = FALSE;
+  _clutter_stage_set_pick_buffer_valid (stage, FALSE);
+  _clutter_stage_reset_picks_per_frame_counter (stage);
 
   /* Before we can paint, we have to be sure we have the latest layout */
   _clutter_stage_maybe_relayout (CLUTTER_ACTOR (stage));
@@ -601,7 +597,7 @@ _clutter_do_pick (ClutterStage   *stage,
   /* It's possible that we currently have a static scene and have renderered a
    * full, unclipped pick buffer. If so we can simply continue to read from
    * this cached buffer until the scene next changes. */
-  if (context->have_complete_pick_buffer)
+  if (_clutter_stage_get_pick_buffer_valid (stage))
     {
       CLUTTER_TIMER_START (_clutter_uprof_context, pick_read);
       cogl_read_pixels (x, y, 1, 1,
@@ -628,7 +624,7 @@ _clutter_do_pick (ClutterStage   *stage,
       goto result;
     }
 
-  context->picks_per_frame++;
+  _clutter_stage_increment_picks_per_frame_counter (stage);
 
   _clutter_backend_ensure_context (context->backend, stage);
 
@@ -638,7 +634,7 @@ _clutter_do_pick (ClutterStage   *stage,
   /* If we are seeing multiple picks per frame that means the scene is static
    * so we promote to doing a non-scissored pick render so that all subsequent
    * picks for the same static scene won't require additional renders */
-  if (context->picks_per_frame < 2)
+  if (_clutter_stage_get_picks_per_frame_counter (stage) < 2)
     {
       if (G_LIKELY (!(clutter_pick_debug_flags &
                       CLUTTER_DEBUG_DUMP_PICK_BUFFERS)))
@@ -680,7 +676,7 @@ _clutter_do_pick (ClutterStage   *stage,
         cogl_clip_pop ();
     }
   else
-    context->have_complete_pick_buffer = TRUE;
+    _clutter_stage_set_pick_buffer_valid (stage, TRUE);
 
   /* Make sure Cogl flushes any batched geometry to the GPU driver */
   cogl_flush ();

clutter/clutter-private.h

@@ -183,9 +183,6 @@ struct _ClutterMainContext
   GList *repaint_funcs;
 
   ClutterSettings *settings;
-
-  gint picks_per_frame;
-  gboolean have_complete_pick_buffer;
 };
 
 #define CLUTTER_CONTEXT()	(_clutter_context_get_default ())
@@ -279,6 +276,12 @@ int      _clutter_stage_get_pending_swaps      (ClutterStage *stage);
 
 gboolean _clutter_stage_has_full_redraw_queued (ClutterStage *stage);
 
+void     _clutter_stage_set_pick_buffer_valid  (ClutterStage *stage, gboolean valid);
+gboolean _clutter_stage_get_pick_buffer_valid  (ClutterStage *stage);
+void     _clutter_stage_increment_picks_per_frame_counter (ClutterStage *stage);
+void     _clutter_stage_reset_picks_per_frame_counter     (ClutterStage *stage);
+guint    _clutter_stage_get_picks_per_frame_counter       (ClutterStage *stage);
+
 /* vfuncs implemented by backend */
 GType         _clutter_backend_impl_get_type  (void);
 

clutter/clutter-stage.c

@@ -116,6 +116,8 @@ struct _ClutterStagePrivate
 
   ClutterStageHint    stage_hints;
 
+  gint                picks_per_frame;
+
   guint redraw_pending         : 1;
   guint is_fullscreen          : 1;
   guint is_cursor_visible      : 1;
@@ -126,6 +128,7 @@ struct _ClutterStagePrivate
   guint min_size_changed       : 1;
   guint dirty_viewport         : 1;
   guint dirty_projection       : 1;
+  guint have_valid_pick_buffer : 1;
 };
 
 enum
@@ -734,6 +737,16 @@ clutter_stage_real_queue_redraw (ClutterActor *actor,
   else
     CLUTTER_CONTEXT ()->redraw_count += 1;
 
+  /* We have an optimization in _clutter_do_pick to detect when the
+   * scene is static so we can cache a full, un-clipped pick buffer to
+   * avoid continuous pick renders.
+   *
+   * Currently the assumption is that actors queue a redraw when some
+   * state changes that affects painting *or* picking so we can use
+   * this point to invalidate any currently cached pick buffer.
+   */
+  _clutter_stage_set_pick_buffer_valid (stage, FALSE);
+
   /* If the backend can't do anything with redraw clips (e.g. it already knows
    * it needs to redraw everything anyway) then don't spend time transforming
    * any clip regions into stage coordinates... */
@@ -1452,6 +1465,9 @@ clutter_stage_init (ClutterStage *self)
 
   _clutter_stage_window_get_geometry (priv->impl, &geom);
   _clutter_stage_set_viewport (self, 0, 0, geom.width, geom.height);
+
+  _clutter_stage_set_pick_buffer_valid (self, FALSE);
+  _clutter_stage_reset_picks_per_frame_counter (self);
 }
 
 /**
@@ -2929,3 +2945,33 @@ clutter_stage_get_no_clear_hint (ClutterStage *stage)
 
   return (stage->priv->stage_hints & CLUTTER_STAGE_NO_CLEAR_ON_PAINT) != 0;
 }
+
+gboolean
+_clutter_stage_get_pick_buffer_valid (ClutterStage *stage)
+{
+  return stage->priv->have_valid_pick_buffer;
+}
+
+void
+_clutter_stage_set_pick_buffer_valid (ClutterStage *stage, gboolean valid)
+{
+  stage->priv->have_valid_pick_buffer = valid;
+}
+
+void
+_clutter_stage_increment_picks_per_frame_counter (ClutterStage *stage)
+{
+  stage->priv->picks_per_frame++;
+}
+
+void
+_clutter_stage_reset_picks_per_frame_counter (ClutterStage *stage)
+{
+  stage->priv->picks_per_frame = 0;
+}
+
+guint
+_clutter_stage_get_picks_per_frame_counter (ClutterStage *stage)
+{
+  return stage->priv->picks_per_frame;
+}