base-types: Add zero point and rect

A constant ClutterPoint for (0, 0) and a constant degenerate ClutterRect
can be useful as guards for pointers, freeing the NULL value to mean
"unset".

clutter/clutter-base-types.c

@@ -377,6 +377,26 @@ G_DEFINE_BOXED_TYPE (ClutterMargin, clutter_margin,
  * ClutterPoint
  */
 
+static const ClutterPoint _clutter_point_zero = CLUTTER_POINT_INIT_ZERO;
+
+/**
+ * clutter_point_zero:
+ *
+ * A point centered at (0, 0).
+ *
+ * The returned value can be used as a guard.
+ *
+ * Return value: a point centered in (0, 0); the returned #ClutterPoint
+ *   is owned by Clutter and it should not be modified or freed.
+ *
+ * Since: 1.12
+ */
+const ClutterPoint *
+clutter_point_zero (void)
+{
+  return &_clutter_point_zero;
+}
+
 /**
  * clutter_point_alloc:
  *
@@ -672,6 +692,8 @@ G_DEFINE_BOXED_TYPE_WITH_CODE (ClutterSize, clutter_size,
  * ClutterRect
  */
 
+static const ClutterRect _clutter_rect_zero = CLUTTER_RECT_INIT_ZERO;
+
 static gboolean clutter_rect_progress (const GValue *a,
                                        const GValue *b,
                                        gdouble       progress,
@@ -705,6 +727,26 @@ clutter_rect_normalize_internal (ClutterRect *rect)
     }
 }
 
+/**
+ * clutter_rect_zero:
+ *
+ * A #ClutterRect with #ClutterRect.origin set at (0, 0) and a size
+ * of 0.
+ *
+ * The returned value can be used as a guard.
+ *
+ * Return value: a rectangle with origin in (0, 0) and a size of 0.
+ *   The returned #ClutterRect is owned by Clutter and it should not
+ *   be modified or freed.
+ *
+ * Since: 1.12
+ */
+const ClutterRect *
+clutter_rect_zero (void)
+{
+  return &_clutter_rect_zero;
+}
+
 /**
  * clutter_rect_alloc:
  *

clutter/clutter-types.h

@@ -161,6 +161,8 @@ struct _ClutterPoint
 CLUTTER_AVAILABLE_IN_1_12
 GType clutter_point_get_type (void) G_GNUC_CONST;
 
+CLUTTER_AVAILABLE_IN_1_12
+const ClutterPoint *    clutter_point_zero      (void);
 CLUTTER_AVAILABLE_IN_1_12
 ClutterPoint *          clutter_point_alloc     (void);
 CLUTTER_AVAILABLE_IN_1_12
@@ -294,6 +296,8 @@ struct _ClutterRect
 CLUTTER_AVAILABLE_IN_1_12
 GType clutter_rect_get_type (void) G_GNUC_CONST;
 
+CLUTTER_AVAILABLE_IN_1_12
+const ClutterRect *     clutter_rect_zero               (void);
 CLUTTER_AVAILABLE_IN_1_12
 ClutterRect *           clutter_rect_alloc              (void);
 CLUTTER_AVAILABLE_IN_1_12

clutter/clutter.symbols

@@ -1044,6 +1044,7 @@ clutter_point_equals
 clutter_point_free
 clutter_point_get_type
 clutter_point_init
+clutter_point_zero
 clutter_profile_flags DATA
 clutter_property_transition_get_property_name
 clutter_property_transition_get_type
@@ -1068,6 +1069,7 @@ clutter_rect_intersection
 clutter_rect_normalize
 clutter_rect_offset
 clutter_rect_union
+clutter_rect_zero
 clutter_rectangle_get_border_color
 clutter_rectangle_get_border_width
 clutter_rectangle_get_color

doc/reference/clutter/clutter-sections.txt

@@ -3187,6 +3187,7 @@ ClutterPaintVolume
 <SUBSECTION>
 CLUTTER_POINT_INIT
 CLUTTER_POINT_INIT_ZERO
+clutter_point_zero
 clutter_point_alloc
 clutter_point_init
 clutter_point_copy
@@ -3206,6 +3207,7 @@ clutter_size_equals
 <SUBSECTION>
 CLUTTER_RECT_INIT
 CLUTTER_RECT_INIT_ZERO
+clutter_rect_zero
 clutter_rect_alloc
 clutter_rect_init
 clutter_rect_copy