[HOpenGL] GLSL interface

[Daniel Bergey]

Thank you.  The example you gave was very helpful in understanding the
use of StateVars.

On 2013-02-20 at 12:49, Claude Heiland-Allen <claude at mathr.co.uk> wrote:
> On 20/02/13 17:26, Daniel Bergey wrote:
>> What is the recommended way to create and use a Shader object?
>
> Personally I tend to use OpenGLRaw package or OpenGLRaw21 package, as
> OpenGL package diverges from all the useful non-Haskell tutorials and
> documentation by a wide margin, and OpenGL package doesn't yet support
> such useful things as geometry shaders.  Anyway, usage is mostly via the
> ObjectName/StateVar interface:
>
>> Graphics.Rendering.OpenGL.GL.Shaders.Shaders has a function createShader
>> which looks good, but is not exported.  Similar not-exported functions
>> seem to exist for the Program type.
>
> -- untested code
> do
>   [vert] <- genObjectNames 1
>   [frag] <- genObjectNames 1
>   [prog] <- genObjectNames 1
>   shaderSource vert $= ["void main() { gl_Position = ftransform(); }"]
>   shaderSource frag $= ["void main() { gl_FragColor = vec4(1.0); }"]
>   compileShader vert
>   compileShader frag
>   attachedShaders prog $= ([vert], [frag])
>   linkProgram prog
>   debugPrint =<< get (programInfoLog prog)
>   currentProgram $= Just prog
>   -- draw using shader here
>   currentProgram $= Nothing