stage: make it possible to queue a relayout only

This adds a private ->relayout_pending boolean similar in spirit to
redraw_pending. This will allow us to queue a relayout without
implicitly queueing a redraw; instead we can depend on the actions
of a relayout to queue any necessary redraw.

clutter/clutter-main.c

@@ -225,47 +225,6 @@ clutter_get_accessibility_enabled (void)
   return cally_get_cally_initialized ();
 }
 
-
-void
-_clutter_stage_maybe_relayout (ClutterActor *stage)
-{
-  gfloat natural_width, natural_height;
-  ClutterActorBox box = { 0, };
-  CLUTTER_STATIC_TIMER (relayout_timer,
-                        "Mainloop", /* no parent */
-                        "Layouting",
-                        "The time spent reallocating the stage",
-                        0 /* no application private data */);
-
-  /* avoid reentrancy */
-  if (!CLUTTER_ACTOR_IN_RELAYOUT (stage))
-    {
-      CLUTTER_TIMER_START (_clutter_uprof_context, relayout_timer);
-      CLUTTER_NOTE (ACTOR, "Recomputing layout");
-
-      CLUTTER_SET_PRIVATE_FLAGS (stage, CLUTTER_IN_RELAYOUT);
-
-      natural_width = natural_height = 0;
-      clutter_actor_get_preferred_size (stage,
-                                        NULL, NULL,
-                                        &natural_width, &natural_height);
-
-      box.x1 = 0;
-      box.y1 = 0;
-      box.x2 = natural_width;
-      box.y2 = natural_height;
-
-      CLUTTER_NOTE (ACTOR, "Allocating (0, 0 - %d, %d) for the stage",
-                    (int) natural_width,
-                    (int) natural_height);
-
-      clutter_actor_allocate (stage, &box, CLUTTER_ALLOCATION_NONE);
-
-      CLUTTER_UNSET_PRIVATE_FLAGS (stage, CLUTTER_IN_RELAYOUT);
-      CLUTTER_TIMER_STOP (_clutter_uprof_context, relayout_timer);
-    }
-}
-
 void
 _clutter_do_redraw (ClutterStage *stage)
 {
@@ -278,9 +237,6 @@ _clutter_do_redraw (ClutterStage *stage)
   _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));
-
   _clutter_backend_ensure_context (ctx->backend, stage);
 
   /* Setup FPS count - not currently across *all* stages rather than per */

clutter/clutter-stage.c

@@ -120,6 +120,7 @@ struct _ClutterStagePrivate
 
   GArray             *paint_volume_stack;
 
+  guint relayout_pending       : 1;
   guint redraw_pending         : 1;
   guint is_fullscreen          : 1;
   guint is_cursor_visible      : 1;
@@ -673,7 +674,54 @@ _clutter_stage_needs_update (ClutterStage *stage)
 
   priv = stage->priv;
 
-  return priv->redraw_pending;
+  return priv->relayout_pending || priv->redraw_pending;
+}
+
+void
+_clutter_stage_maybe_relayout (ClutterActor *actor)
+{
+  ClutterStage *stage = CLUTTER_STAGE (actor);
+  ClutterStagePrivate *priv = stage->priv;
+  gfloat natural_width, natural_height;
+  ClutterActorBox box = { 0, };
+  CLUTTER_STATIC_TIMER (relayout_timer,
+                        "Mainloop", /* no parent */
+                        "Layouting",
+                        "The time spent reallocating the stage",
+                        0 /* no application private data */);
+
+  if (!priv->relayout_pending)
+    return;
+  priv->relayout_pending = FALSE;
+
+  /* avoid reentrancy */
+  if (!CLUTTER_ACTOR_IN_RELAYOUT (stage))
+    {
+      CLUTTER_TIMER_START (_clutter_uprof_context, relayout_timer);
+      CLUTTER_NOTE (ACTOR, "Recomputing layout");
+
+      CLUTTER_SET_PRIVATE_FLAGS (stage, CLUTTER_IN_RELAYOUT);
+
+      natural_width = natural_height = 0;
+      clutter_actor_get_preferred_size (CLUTTER_ACTOR (stage),
+                                        NULL, NULL,
+                                        &natural_width, &natural_height);
+
+      box.x1 = 0;
+      box.y1 = 0;
+      box.x2 = natural_width;
+      box.y2 = natural_height;
+
+      CLUTTER_NOTE (ACTOR, "Allocating (0, 0 - %d, %d) for the stage",
+                    (int) natural_width,
+                    (int) natural_height);
+
+      clutter_actor_allocate (CLUTTER_ACTOR (stage),
+                              &box, CLUTTER_ALLOCATION_NONE);
+
+      CLUTTER_UNSET_PRIVATE_FLAGS (stage, CLUTTER_IN_RELAYOUT);
+      CLUTTER_TIMER_STOP (_clutter_uprof_context, relayout_timer);
+    }
 }
 
 /**
@@ -693,17 +741,15 @@ _clutter_stage_do_update (ClutterStage *stage)
 
   priv = stage->priv;
 
-  if (!priv->redraw_pending)
+  /* NB: We need to ensure we have an up to date layout *before* we
-    return FALSE;
+   * check or clear the pending redraws flag since a relayout may
-
+   * queue a redraw.
-  /* clutter_do_redraw() will also call maybe_relayout(), but since a relayout
-   * can queue a redraw, we want to do the relayout before we clear the
-   * update_idle to avoid painting the stage twice. Calling maybe_relayout()
-   * twice in a row is cheap because of caching of requested and allocated
-   * size.
    */
   _clutter_stage_maybe_relayout (CLUTTER_ACTOR (stage));
 
+  if (!priv->redraw_pending)
+    return FALSE;
+
   CLUTTER_NOTE (PAINT, "redrawing via idle for stage[%p]", stage);
   _clutter_do_redraw (stage);
 
@@ -721,6 +767,20 @@ _clutter_stage_do_update (ClutterStage *stage)
   return TRUE;
 }
 
+static void
+clutter_stage_real_queue_relayout (ClutterActor *self)
+{
+  ClutterStage *stage = CLUTTER_STAGE (self);
+  ClutterStagePrivate *priv = stage->priv;
+  ClutterActorClass *parent_class;
+
+  priv->relayout_pending = TRUE;
+
+  /* chain up */
+  parent_class = CLUTTER_ACTOR_CLASS (clutter_stage_parent_class);
+  parent_class->queue_relayout (self);
+}
+
 static void
 clutter_stage_real_queue_redraw (ClutterActor *actor,
                                  ClutterActor *leaf)
@@ -1112,6 +1172,7 @@ clutter_stage_class_init (ClutterStageClass *klass)
   actor_class->unrealize = clutter_stage_unrealize;
   actor_class->show = clutter_stage_show;
   actor_class->hide = clutter_stage_hide;
+  actor_class->queue_relayout = clutter_stage_real_queue_relayout;
   actor_class->queue_redraw = clutter_stage_real_queue_redraw;
   actor_class->apply_transform = clutter_stage_real_apply_transform;
 
@@ -1471,6 +1532,8 @@ clutter_stage_init (ClutterStage *self)
   priv->fog.z_near = 1.0;
   priv->fog.z_far  = 2.0;
 
+  priv->relayout_pending = TRUE;
+
   clutter_actor_set_reactive (CLUTTER_ACTOR (self), TRUE);
   clutter_stage_set_title (self, g_get_prgname ());
   clutter_stage_set_key_focus (self, NULL);
@@ -2617,6 +2680,7 @@ clutter_stage_ensure_redraw (ClutterStage *stage)
   g_return_if_fail (CLUTTER_IS_STAGE (stage));
 
   priv = stage->priv;
+  priv->relayout_pending = TRUE;
   priv->redraw_pending = TRUE;
 
   master_clock = _clutter_master_clock_get_default ();