Limitations of viewporter

The viewporter only allows integral destination size (which matches the integral positions of subsurfaces).

I was trying to effectively render a dmabuf at fractional position/size by rounding up the fractional destination size, and then calculating a source rectangle that extends by a little bit outside the buffer dimensions.

Sadly, the viewporter protocol does not allow my to specify such a source rectangle, but it would be very useful for this case.

If you allow it, maybe you need edge modes like GL textures to define the content of the 'outside pixels'. But transparent black would work just fine for my case.