[gegl] Added gegl_rectangle_is_empty function

[Martin Nordholts <martinn src gnome org>]

commit 2e789d36584daa09bf5f3968f1adb93a922a7a93
Author: Danny Robson <danny blubinc net>
Date:   Sat Jun 5 18:09:19 2010 +1000

    Added gegl_rectangle_is_empty function

 gegl/gegl-utils.c |   13 +++++++++++++
 gegl/gegl-utils.h |   10 ++++++++++
 2 files changed, 23 insertions(+), 0 deletions(-)
---
diff --git a/gegl/gegl-utils.c b/gegl/gegl-utils.c
index e80c955..8df8914 100644
--- a/gegl/gegl-utils.c
+++ b/gegl/gegl-utils.c
@@ -127,6 +127,8 @@
   gegl_rectangle_contains (const GeglRectangle *r,
                            const GeglRectangle *s)
   {
+    g_return_val_if_fail (r && s, FALSE);
+
     if (s->x >= r->x &&
         s->y >= r->y &&
         (s->x + s->width) <= (r->x + r->width) &&
@@ -140,6 +142,8 @@
   gegl_rectangle_equal (const GeglRectangle *r,
                         const GeglRectangle *s)
   {
+    g_return_val_if_fail (r && s, FALSE);
+
     if (r->x == s->x &&
         r->y == s->y &&
         r->width == s->width &&
@@ -156,6 +160,8 @@
                                gint                 w,
                                gint                 h)
   {
+    g_return_val_if_fail (r, FALSE);
+
     if (r->x == x &&
         r->y == y &&
         r->width == w &&
@@ -165,6 +171,13 @@
       return FALSE;
   }
 
+  gboolean
+  gegl_rectangle_is_empty (const GeglRectangle *r)
+  {
+    g_return_val_if_fail (r != NULL, FALSE);
+    return r->width == 0 && r->height == 0;
+  }
+
   static GeglRectangle *
   gegl_rectangle_dup (const GeglRectangle *rectangle)
   {
diff --git a/gegl/gegl-utils.h b/gegl/gegl-utils.h
index 10c038c..3a56b99 100644
--- a/gegl/gegl-utils.h
+++ b/gegl/gegl-utils.h
@@ -88,6 +88,16 @@ gboolean    gegl_rectangle_equal_coords  (const GeglRectangle *rectangle,
                                           gint                 height);
 
 /**
+ * gegl_rectangle_is_empty:
+ * @rectangle: a #GeglRectangle
+ *
+ * Check if a rectangle has zero area.
+ *
+ * Returns TRUE if @rectangle height and width are both zero.
+ */
+gboolean    gegl_rectangle_is_empty     (const GeglRectangle *rectangle);
+
+/**
  * gegl_rectangle_copy:
  * @destination: a #GeglRectangle
  * @source: a #GeglRectangle