[mutter] clutter/actor-box: Allow marking boxes as uninitialized

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

commit 0bfb995bffeb846cb574d1f6762b1440fad7272d
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Sat Jun 6 12:55:07 2020 +0200

    clutter/actor-box: Allow marking boxes as uninitialized
    
    Add support for an artificial UNINITIALIZED marking for ClutterActorBox,
    done by setting the boxes origin to Infinity and its size to -Infinity.
    That is a value that's considered an invalid allocation by Clutter and
    which can never be set by sane code.
    
    This will allow setting the allocation of ClutterActors to an
    UNINITIALIZED box when creating actors or when removing them from the
    scenegraph and makes it possible to explicitely detect uninitialized
    allocations, which is useful in a few cases.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1290

 clutter/clutter/clutter-actor-box.c | 26 ++++++++++++++++++++++++++
 clutter/clutter/clutter-types.h     | 17 +++++++++++++++++
 2 files changed, 43 insertions(+)
---
diff --git a/clutter/clutter/clutter-actor-box.c b/clutter/clutter/clutter-actor-box.c
index a2308ac314..9e30c62bd7 100644
--- a/clutter/clutter/clutter-actor-box.c
+++ b/clutter/clutter/clutter-actor-box.c
@@ -615,6 +615,32 @@ clutter_actor_box_scale (ClutterActorBox *box,
   box->y2 *= scale;
 }
 
+/**
+ * clutter_actor_box_is_initialized:
+ * @box: a #ClutterActorBox
+ *
+ * Checks if @box has been initialized, a #ClutterActorBox is uninitialized
+ * if it has a size of -1 at an origin of 0, 0.
+ *
+ * Returns: %TRUE if the box is uninitialized, %FALSE if it isn't
+ */
+gboolean
+clutter_actor_box_is_initialized (ClutterActorBox *box)
+{
+  gboolean x1_uninitialized, x2_uninitialized;
+  gboolean y1_uninitialized, y2_uninitialized;
+
+  g_return_val_if_fail (box != NULL, TRUE);
+
+  x1_uninitialized = isinf (box->x1);
+  x2_uninitialized = isinf (box->x2) && signbit (box->x2);
+  y1_uninitialized = isinf (box->y1);
+  y2_uninitialized = isinf (box->y2) && signbit (box->y2);
+
+  return !x1_uninitialized || !x2_uninitialized ||
+         !y1_uninitialized || !y2_uninitialized;
+}
+
 G_DEFINE_BOXED_TYPE_WITH_CODE (ClutterActorBox, clutter_actor_box,
                                clutter_actor_box_copy,
                                clutter_actor_box_free,
diff --git a/clutter/clutter/clutter-types.h b/clutter/clutter/clutter-types.h
index 1b65573a3c..0c6400d93e 100644
--- a/clutter/clutter/clutter-types.h
+++ b/clutter/clutter/clutter-types.h
@@ -174,6 +174,20 @@ struct _ClutterActorBox
  */
 #define CLUTTER_ACTOR_BOX_INIT_ZERO                     CLUTTER_ACTOR_BOX_INIT (0.f, 0.f, 0.f, 0.f)
 
+/**
+ * CLUTTER_ACTOR_BOX_UNINITIALIZED:
+ *
+ * A simple macro for creating a #ClutterActorBox with a size of -1 when
+ * declaring it, e.g.:
+ *
+ * |[
+ *   ClutterActorBox box = CLUTTER_ACTOR_BOX_UNINITIALIZED;
+ * ]|
+ */
+
+
+#define CLUTTER_ACTOR_BOX_UNINITIALIZED { .x1 = INFINITY, .y1 = INFINITY, .x2 = -INFINITY, .y2 = -INFINITY }
+
 CLUTTER_EXPORT
 GType            clutter_actor_box_get_type      (void) G_GNUC_CONST;
 CLUTTER_EXPORT
@@ -252,6 +266,9 @@ CLUTTER_EXPORT
 void             clutter_actor_box_scale          (ClutterActorBox       *box,
                                                    gfloat                 scale);
 
+CLUTTER_EXPORT
+gboolean         clutter_actor_box_is_initialized (ClutterActorBox       *box);
+
 /**
  * ClutterKnot:
  * @x: X coordinate of the knot