[GSdx GUI] Clutter in the renderer dropdown menu

[refraction]

It might be possible to make release builds just have the 2 directx modes, opengl and opengl software (for linux compatibility), null isn't really needed for release either, so there's an option.

[gregory]

I removed null on linux. I think the only goal is for benchmark.
Anyway the API used by the sw renderer is a big subset of the api used in the hw renderer (no associated cost).
To push the final frame you need to setup
1/ vertices
2/ input texture
3/ parameter of the call (uniform)
4/ shader pipeline
5/ output buffer
6 / configure blending etc...

HW renderer does exactly the same. The only difference is the number of vertices and the texture color