kgl-opengl on macOS creates 2.1 context instead of 4.1 context by default

[nlbuescher]

kgl-opengl currently can only create an OpenGL context up version 2.1, because Apple. Platform lib only supports up to 3.2+ (no 4), but there's nothing to be done about that. Calling gl functions from 4+ throws NullPointerException because the function loader can't find them.

[Dominaezzz]

kgl-opengl can load functions from 3.2. I've tested this on at least three macs. Are you experiencing any specific issues with function loading?

[nlbuescher]

It can load the functions, but the context version returned from glGetString(GL_VERSION) is 2.1 when using GLFW (ie initializing context without specifying version). This may affect shader compilation, although I'm not sure about that. Would need to test.

Relevant stack overflow link: https://stackoverflow.com/a/26982694

[nlbuescher]

Update after a bit more research:

1. The latest version on OpenGL supported by Apple seems to be 4.1 (link), which is better than I thought.
2. Despite that, if the context is initialized as 2.1, my #version 330 shader does not compile because version 330 is not supported.

Calling glutInitDisplayMode(GLUT_3_2_CORE_PROFILE) from the OpenGL3 platform lib get a glGetString(GL_VERSION) result of 4.1, otherwise the context version is similarly defaulted to 2.1. Not sure what the implications of that are.

[Dominaezzz]

I'll try and also look into this but without a Mac it'll take me a while. It should just mean updating the Loader class for the macosMain sourceSet.

[nlbuescher]

This is actually documented behavior of GLFW on macOS (link)

Might be helpful to link to the GLFW FAQ in the README so issue reports like this don't happen again 😅

EDIT: Forgot to mention that I tested the instructions in the FAQ and they successfully create a 4.1 context (although my textures don't seem to load, but that's a different thing entirely because of the API differences)