This problem baffles me. I am testing some Haskell bindings to OpenGL, I create a vertex shader, a fragment shader, compile the program, and draw a textured rectangle to the screen after transforming the vertices… except the screen is blank.
When I render the rectangle flat white instead of using a sampler in the fragment shader, it works fine. When I go into gdebugger and use the option to replace all textures with a stub texture, it also works fine.
When I look at the allocated textures in gdebugger, there are no texture objects, only the default 2d texture. When I set a breakpoint on glTexImage2d, I see that it is being called, but no texture object appears in memory when I peek at it with gdebugger.
What’s going on? Am I forgetting to set some environment variables? I’m quite frustrated. The kicker is that I had this problem before, and I managed to fix it then, but I forgot what the problem was. I hate myself >_>
I ported a tutorial on OpenGL to Haskell some time ago. It includes a link to a very tiny library that, among other things, helps with loading textures.
Perhaps you could compare that code with what you have to spot the differences.