Functions to support using cairo

Cairo is a graphics library that supports vector graphics and image compositing that can be used with GTK.

GDK does not wrap the Cairo API; instead it allows to create Cairo drawing contexts which can be used to draw on GdkSurfaces.

Additional functions allow use GdkRectangles with Cairo and to use GdkRGBA, GdkPixbuf, and GdkSurface instances as sources for drawing operations.

For more information on Cairo, please see the Cairo API reference.