[cairo] Large number of glReadPixel method calls

[Carl Worth]

On Thu, 29 Jul 2004 17:41:26 +0200, David Reveman wrote:
> I'm guessing that the matrox XiG driver doesn't support this extension, which
> means that cairo will fall-back to software rendering of every glyph (reading
> the complete destination surface with glReadPixels into a local image buffer,
> render the glyph to this image buffer and then transfer the result back
> to the destination surface).

For when software fallback really is necessary, we should fix this so
that it reads back only a rectangle the size of the intersection of the
target surface bounds and the bounds of the current drawing operation.

-Carl