The X11 backend uses a shadow buffer to be able to support transformed
outputs. However, this belongs in the renderer, since otherwise this
code would have to be copied into every backend that uses the pixman
renderer and supports transformed outputs.
This renderer could be used when there's no graphic accelerator available,
for example in (future) KMS and fbdev backends.
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Ander Conselvan de Oliveira