https://bugs.freedesktop.org/show_bug.cgi?id=57875
--- Comment #29 from Stefan Dösinger stefandoesinger@gmx.at --- Hmm, this seems like an idea worth thinking about. The D3D behavior the proposed extension addresses is part of the D3DDECLUSAGE_POSITIONT / D3DFVF_XYZRHW vertex input semantics.
For now I'm opposed to making this a vertex shader control though. The point of POSITIONT / XYZRHW is to skip vertex processing altogether, so handling POSITIONT semantics in a shader seems a bit off. Furthermore, the clipping behavior of POSITIONT depends on the depth test, so this needs a separate control anyway (or replicating the depth test interaction, which seems somewhat ugly to me because its done by a different stage in the rendering pipeline).