Open GL extensions, dglut style

[downs]

AxelS wrote:
> Hello evrybody...
> 
> I want to use all the opengl extensions like Shaders in my D2.0 prog...
> I already got the opengl32.lib and also the headers...
> 
> I tried it wglGetProc (similar name...)! I could compile it but it hangs up 
> runtime and creates errors which dont tell me the actual problem...
> and yes, I'm sure that these functions which I want to get are existing!
> I know the usage of predefined function variables is recommended...
> I tried but failed...
> 
> Thanks in advance!

This is how we do it in dglut:

version(Win32) {
  extern(System) void* wglGetProcAddress(char* procName);
  alias wglGetProcAddress getExtProc;
} else {
  extern(C) void* glXGetProcAddressARB(char* procName);
  alias glXGetProcAddressARB getExtProc;
}

template SysFunc(C) { extern(System) alias ReturnType!(C) 
function(ParameterTypeTuple!(C)) SysFunc; }

struct ExtFunc(C, string name) {
  static {
    SysFunc!(C) load() {
      static if (is(typeof(&getExtProc))) {
        return cast(SysFunc!(C)) getExtProc(toStringz("gl"~name));
      } else static assert(false, "Platform not supported (yet)");
    }
    SysFunc!(C) fn;
    ReturnType!(C) opCall(ParameterTypeTuple!(C) params) {
      if (!fn) fn=cast(typeof(fn)) load();
      if (!fn) throw new Exception("Extension function \""~name~"\" not found 
in lookup table!");
      return fn(params);
    }
  }
}


Then later on, they're used like this:

    alias ExtFunc!(void function(GLenum, GLenum, GLenum, int *), 
"GetFramebufferAttachmentParameterivEXT") getpar;
    foreach (where, obj; attachedObjects) {
      int res, res2;
      getpar(GL_FRAMEBUFFER_EXT, where, 
GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE_EXT, &res);
      getpar(GL_FRAMEBUFFER_EXT, where, 
GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME_EXT, &res2);