SDL2 OpenGL3 example not working on OSX 10.11.2 / Geforce 9400M

[spate]

The SDL + OpenGL 3 example app isn't working on OSX 10.11.2 on my Geforce 9400M. The SDL + OpenGL (compatibility) example app is working fine. (Using top of tree.)

[Erkaman]

Same thing happens for me on OS X 10.10.3. sdl_opengl_example works fine, but in sdl_opengl3_example no windows are drawn:

[ocornut]

Issue was reported recently in #463 but not solved. I haven't personally tried this code on a Mac.

Could you try: a/ the suggestions in that other thread? b/ disabling scissoring in the render function and see if it makes a difference?

Otherwise have a look at whatever error reporting SDL2 offers, it may give a clue. The core profile version looks definitively wrong to me but the poster of the other thread said it didn't fix the issue.

[Erkaman]

I have been able to solve the problem: Go to sdl_opengl3_example/main.cpp and replace this code:

    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

With this:

    SDL_GL_SetAttribute (SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG);
    SDL_GL_SetAttribute (SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

The problem with the original code was that an OpenGL context of version 2.2(a compability profile) was created. However, the shaders in imgui_impl_sdl_gl3.cpp were using shader version 330, and this version can only be used in a core profile. Thus they would not compile.

So a core profile had to be created instead. However, you must be very careful when creating a core profile on mac. You have to set SDL_GL_CONTEXT_FLAGS to SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG and set SDL_GL_CONTEXT_PROFILE_MASK to SDL_GL_CONTEXT_PROFILE_CORE. Otherwise, it will fail.

[ocornut]

Thanks for looking into it
It looks like SDL_GL_SetAttribute (SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE); was missing from my proposed fix in #463
I will merge the fix in master shortly!

[ocornut]

Closing, thanks!