[cairo] [PATCH 1/2] gl: Add a first bit of general documentation on cairo-gl usage.

[Benjamin Otte]

On Wed, 2011-02-02 at 17:13 -0800, Bill Spitzak wrote:
> 3. If no cairo_t is using a surface as a destination, it can then have 
> *any* number of cairo_t's using it as a source.
> 
The proposed patch breaks this.