[mutter] clutter/stage: Add signals for different update stages

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

commit 2afe3e922344a77f42afd388ad6c2ac456b314ce
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri May 29 20:25:07 2020 +0200

    clutter/stage: Add signals for different update stages
    
    Right now the stage only had a signal called 'after-paint' which was not
    tied to painting but updating. Change this to offer 4 signals, for the 4
    different stages:
    
     * before-update - emitted in the beginning before the actual stage
       updating
    
     * before-paint - emitted before painting if there will be any stage
       painting
    
     * after-paint - emitted after painting if there was any stage painting
    
     * after-update - emitted as a last step of updating, no matter whether
       there were any painting or not
    
    Currently there were only one listener, that should only really have
    been called if there was any painting, so no changes to listeners are
    needed.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285

 clutter/clutter/clutter-stage-private.h   |  5 ++-
 clutter/clutter/clutter-stage.c           | 69 ++++++++++++++++++++++++++++++-
 clutter/clutter/cogl/clutter-stage-cogl.c | 18 +++++++-
 3 files changed, 88 insertions(+), 4 deletions(-)
---
diff --git a/clutter/clutter/clutter-stage-private.h b/clutter/clutter/clutter-stage-private.h
index 8076c32565..866731100d 100644
--- a/clutter/clutter/clutter-stage-private.h
+++ b/clutter/clutter/clutter-stage-private.h
@@ -40,7 +40,10 @@ void                clutter_stage_paint_view             (ClutterStage
                                                           ClutterStageView      *view,
                                                           const cairo_region_t  *redraw_clip);
 
-void                _clutter_stage_emit_after_paint      (ClutterStage          *stage);
+void                clutter_stage_emit_before_update     (ClutterStage          *stage);
+void                clutter_stage_emit_before_paint      (ClutterStage          *stage);
+void                clutter_stage_emit_after_paint       (ClutterStage          *stage);
+void                clutter_stage_emit_after_update      (ClutterStage          *stage);
 
 CLUTTER_EXPORT
 void                _clutter_stage_set_window            (ClutterStage          *stage,
diff --git a/clutter/clutter/clutter-stage.c b/clutter/clutter/clutter-stage.c
index 7539dae958..1d08cd4fad 100644
--- a/clutter/clutter/clutter-stage.c
+++ b/clutter/clutter/clutter-stage.c
@@ -167,7 +167,10 @@ enum
   ACTIVATE,
   DEACTIVATE,
   DELETE_EVENT,
+  BEFORE_UPDATE,
+  BEFORE_PAINT,
   AFTER_PAINT,
+  AFTER_UPDATE,
   PAINT_VIEW,
   PRESENTED,
 
@@ -890,11 +893,29 @@ clutter_stage_paint_view (ClutterStage         *stage,
 }
 
 void
-_clutter_stage_emit_after_paint (ClutterStage *stage)
+clutter_stage_emit_before_update (ClutterStage *stage)
+{
+  g_signal_emit (stage, stage_signals[BEFORE_UPDATE], 0);
+}
+
+void
+clutter_stage_emit_before_paint (ClutterStage *stage)
+{
+  g_signal_emit (stage, stage_signals[BEFORE_PAINT], 0);
+}
+
+void
+clutter_stage_emit_after_paint (ClutterStage *stage)
 {
   g_signal_emit (stage, stage_signals[AFTER_PAINT], 0);
 }
 
+void
+clutter_stage_emit_after_update (ClutterStage *stage)
+{
+  g_signal_emit (stage, stage_signals[AFTER_UPDATE], 0);
+}
+
 static gboolean
 clutter_stage_get_paint_volume (ClutterActor *self,
                                 ClutterPaintVolume *volume)
@@ -1438,6 +1459,8 @@ _clutter_stage_do_update (ClutterStage *stage)
 
   COGL_TRACE_BEGIN_SCOPED (ClutterStageDoUpdate, "Update");
 
+  clutter_stage_emit_before_update (stage);
+
   /* NB: We need to ensure we have an up to date layout *before* we
    * check or clear the pending redraws flag since a relayout may
    * queue a redraw.
@@ -1445,7 +1468,10 @@ _clutter_stage_do_update (ClutterStage *stage)
   clutter_stage_maybe_relayout (CLUTTER_ACTOR (stage));
 
   if (!priv->redraw_pending)
-    return FALSE;
+    {
+      clutter_stage_emit_after_update (stage);
+      return FALSE;
+    }
 
   clutter_stage_update_actor_stage_views (stage);
   clutter_stage_maybe_finish_queue_redraws (stage);
@@ -1469,6 +1495,8 @@ _clutter_stage_do_update (ClutterStage *stage)
 
   clutter_stage_update_devices (stage, devices);
 
+  clutter_stage_emit_after_update (stage);
+
   return TRUE;
 }
 
@@ -1997,6 +2025,31 @@ clutter_stage_class_init (ClutterStageClass *klass)
                   G_TYPE_BOOLEAN, 1,
                   CLUTTER_TYPE_EVENT | G_SIGNAL_TYPE_STATIC_SCOPE);
 
+  /**
+   * ClutterStage::before-update:
+   * @stage: the #ClutterStage
+   */
+  stage_signals[BEFORE_UPDATE] =
+    g_signal_new (I_("before-update"),
+                  G_TYPE_FROM_CLASS (gobject_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+
+  /**
+   * ClutterStage::before-paint:
+   * @stage: the stage that received the event
+   *
+   * The ::before-paint signal is emitted before the stage is painted.
+   */
+  stage_signals[BEFORE_PAINT] =
+    g_signal_new (I_("before-paint"),
+                  G_TYPE_FROM_CLASS (gobject_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
   /**
    * ClutterStage::after-paint:
    * @stage: the stage that received the event
@@ -2015,6 +2068,18 @@ clutter_stage_class_init (ClutterStageClass *klass)
                   NULL, NULL, NULL,
                   G_TYPE_NONE, 0);
 
+  /**
+   * ClutterStage::after-update:
+   * @stage: the #ClutterStage
+   */
+  stage_signals[AFTER_UPDATE] =
+    g_signal_new (I_("after-update"),
+                  G_TYPE_FROM_CLASS (gobject_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+
   /**
    * ClutterStage::paint-view:
    * @stage: the stage that received the event
diff --git a/clutter/clutter/cogl/clutter-stage-cogl.c b/clutter/clutter/cogl/clutter-stage-cogl.c
index 565f2f9fbb..af3a6da744 100644
--- a/clutter/clutter/cogl/clutter-stage-cogl.c
+++ b/clutter/clutter/cogl/clutter-stage-cogl.c
@@ -790,11 +790,26 @@ static void
 clutter_stage_cogl_redraw (ClutterStageWindow *stage_window)
 {
   ClutterStageCogl *stage_cogl = CLUTTER_STAGE_COGL (stage_window);
+  gboolean has_redraw_clip = FALSE;
   gboolean swap_event = FALSE;
   GList *l;
 
   COGL_TRACE_BEGIN (ClutterStageCoglRedraw, "Paint (Cogl Redraw)");
 
+  for (l = _clutter_stage_window_get_views (stage_window); l; l = l->next)
+    {
+      ClutterStageView *view = l->data;
+
+      if (!clutter_stage_view_has_redraw_clip (view))
+        continue;
+
+      has_redraw_clip = TRUE;
+      break;
+    }
+
+  if (has_redraw_clip)
+    clutter_stage_emit_before_paint (stage_cogl->wrapper);
+
   for (l = _clutter_stage_window_get_views (stage_window); l; l = l->next)
     {
       ClutterStageView *view = l->data;
@@ -817,7 +832,8 @@ clutter_stage_cogl_redraw (ClutterStageWindow *stage_window)
         }
     }
 
-  _clutter_stage_emit_after_paint (stage_cogl->wrapper);
+  if (has_redraw_clip)
+    clutter_stage_emit_after_paint (stage_cogl->wrapper);
 
   _clutter_stage_window_finish_frame (stage_window);