external: Replace glbinding by glad

[scribam]

Close #489

Warning: the release build of glad doesn't include pre/post callbacks so I didn't replace the before_callback/after_callback functions by a "glad" equivalent. I am not sure if I should use the debug build to have these callbacks, specially if it can affect performance as mentioned in Dav1dde/glad#132. Any advice?

[pent0]

Thanks for taking this work, it's pretty heavy and time-consuming.
I think you need to run clang-format. I notice there are some places where tabs mixed in

[pent0]

Will leave the ideas of debug GLAD to another devs. Maybe discuss here or on Discord

[petmac]

Is this better than SDL_opengl.h? The reason to use glbinding was for profiling and error checking, which I expect glad doesn’t do.

Also, I’m confused why all the GLenums changed to GLints. That didn’t seem right.

[scribam]

@pent0 My bad, I forgot to run clang-format before to push. It should be ok now.

not relevant anymore

[VelocityRa]

The error checks should definitely be kept for Debug mode.
You could make it a compile-time switch to turn them off optionally if they're that slow.

[scribam]

@petmac glTexParameteriv's third argument type is const GLint * params (see https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glTexParameter.xhtml) that's why I changed the type of the swizzle variable here https://github.com/Vita3K/Vita3K/blob/master/src/emulator/renderer/src/texture.cpp#L29 and to all translate_swizzle functions. glbinding casts the GLenum to a GLint which is why it wasn't an issue:

void glTexParameteriv(GLenum target, GLenum pname, const GLenum * params)
{
    glTexParameteriv(target, pname, reinterpret_cast<const GLint *>(params));
}

I can revert the code related to the GLenums to do something like that if you prefer:

const GLint *const swizzle = reinterpret_cast<const GLint *>(translate_swizzle(fmt));