clutter: Also log overlap regions in ClutterPickContext/Stack

These may be used for optimizations once we find the pick actor,
so picking can be avoided in areas we know didn't cross into
other actors. Nothing makes use of it yet though, just log these
so far.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1915>

clutter/clutter/clutter-actor.c

@@ -3960,7 +3960,10 @@ clutter_actor_pick (ClutterActor       *actor,
 
       clutter_paint_volume_to_box (&priv->last_paint_volume, &box);
       if (!clutter_pick_context_intersects_box (pick_context, &box))
-        goto out;
+        {
+          clutter_pick_context_log_overlap (pick_context, actor);
+          goto out;
+        }
     }
 
   if (priv->enable_model_view_transform)

clutter/clutter/clutter-pick-context.c

@@ -118,6 +118,20 @@ clutter_pick_context_log_pick (ClutterPickContext    *pick_context,
   clutter_pick_stack_log_pick (pick_context->pick_stack, box, actor);
 }
 
+/**
+ * clutter_pick_context_log_overlap:
+ * @pick_context: a #ClutterPickContext
+ * @actor: a #ClutterActor
+ *
+ * Logs an overlapping actor into the pick stack.
+ */
+void
+clutter_pick_context_log_overlap (ClutterPickContext *pick_context,
+                                  ClutterActor       *actor)
+{
+  clutter_pick_stack_log_overlap (pick_context->pick_stack, actor);
+}
+
 /**
  * clutter_pick_context_push_clip:
  * @pick_context: a #ClutterPickContext

clutter/clutter/clutter-pick-context.h

@@ -50,6 +50,9 @@ CLUTTER_EXPORT
 void clutter_pick_context_log_pick (ClutterPickContext    *pick_context,
                                     const ClutterActorBox *box,
                                     ClutterActor          *actor);
+CLUTTER_EXPORT
+void clutter_pick_context_log_overlap (ClutterPickContext *pick_context,
+                                       ClutterActor       *actor);
 
 CLUTTER_EXPORT
 void clutter_pick_context_push_clip (ClutterPickContext    *pick_context,

clutter/clutter/clutter-pick-stack-private.h

@@ -42,6 +42,8 @@ void clutter_pick_stack_seal (ClutterPickStack *pick_stack);
 void clutter_pick_stack_log_pick (ClutterPickStack      *pick_stack,
                                   const ClutterActorBox *box,
                                   ClutterActor          *actor);
+void clutter_pick_stack_log_overlap (ClutterPickStack *pick_stack,
+                                     ClutterActor     *actor);
 
 void clutter_pick_stack_push_clip (ClutterPickStack      *pick_stack,
                                    const ClutterActorBox *box);

clutter/clutter/clutter-pick-stack.c

@@ -32,6 +32,7 @@ typedef struct
   Record base;
   ClutterActor *actor;
   int clip_index;
+  gboolean is_overlap;
 } PickRecord;
 
 typedef struct
@@ -342,6 +343,7 @@ clutter_pick_stack_log_pick (ClutterPickStack       *pick_stack,
 
   g_assert (!pick_stack->sealed);
 
+  rec.is_overlap = FALSE;
   rec.actor = actor;
   rec.clip_index = pick_stack->current_clip_stack_top;
   rec.base.rect = *box;
@@ -352,6 +354,21 @@ clutter_pick_stack_log_pick (ClutterPickStack       *pick_stack,
   g_array_append_val (pick_stack->vertices_stack, rec);
 }
 
+void
+clutter_pick_stack_log_overlap (ClutterPickStack *pick_stack,
+                                ClutterActor     *actor)
+{
+  PickRecord rec = { 0 };
+
+  g_assert (!pick_stack->sealed);
+
+  rec.is_overlap = TRUE;
+  rec.actor = actor;
+  rec.clip_index = pick_stack->current_clip_stack_top;
+
+  g_array_append_val (pick_stack->vertices_stack, rec);
+}
+
 void
 clutter_pick_stack_push_clip (ClutterPickStack      *pick_stack,
                               const ClutterActorBox *box)
@@ -428,7 +445,8 @@ clutter_pick_stack_search_actor (ClutterPickStack         *pick_stack,
       PickRecord *rec =
         &g_array_index (pick_stack->vertices_stack, PickRecord, i);
 
-      if (rec->actor && ray_intersects_record (pick_stack, rec, point, ray))
+      if (!rec->is_overlap && rec->actor &&
+          ray_intersects_record (pick_stack, rec, point, ray))
         return rec->actor;
     }