* gdk_rectangle_union:
* @src1: a #GdkRectangle
* @src2: a #GdkRectangle
- * @dest: return location for the union of @src1 and @src2
+ * @dest: (out): return location for the union of @src1 and @src2
*
* Calculates the union of two rectangles.
* The union of rectangles @src1 and @src2 is the smallest rectangle which