WineD3D: WineD3D: Use the shader backend to enable / disable atifs and nvts

[Ivan Gyurdiev]

Stefan Dösinger wrote:
> Alexandre didn't commit the patch, I think we should come to an agreement on 
> this issue, otherwise it is going to come up again and again.
>   
The fundamental issue is pretty straightforward - not sure why it's so 
difficult to come to an agreement.

    - You want to mix and match vertex and fragment GL backends
    - The only maintainable way to do that is to define an interface 
between vertex and fragment objects

    - You're concerned about the interface constraining the ability of 
fragment to talk to vertex
    - Write a smarter interface, I also suggested an object to manage it 
(linker).

You can't have it both ways - ability to mix and match backends, and 
unconstrained interface. The interface doesn't have to be "the lowest 
common denominator" - it could be the highest common denominator if 
properly written. As Henri pointed out the fact that both GL and the 
hardware are vertex/fragment aligned naturally suggests we should break 
up things the same way. Even the D3D programmable pipeline is broken up 
this way (there are Pixel and Vertex shader objects) - and the fixed 
pipeline is going away, so if anything we should move away from its 
interface.

    - You want to replace the fixed pipeline using GL shaders.
    - Then replace the fixed pipeline - this has nothing to do with the 
programmable pipeline, therefore should not affect any programmable 
pipeline interfaces.

You've pointed out that shader_backend_t is more aligned to a GL 
extension than it is to a D3D shader. If that's the case I see little 
value to having that interface - it will just cause confusion as 
unrelated functionalities are packed into it. The disparity between GL 
extensions will get greater as we try to add new features using a 
particular extension, and we'll see a lot of functions that are just 
empty forwards to other "shader backends", since they don't support 
something themselves.

Ivan