Setting the OpenGL version to 2.0 appears to do nothing, as 3.3+ features still work

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Someone was asking me for a test with OpenGL 2.x since they have hardware that supports only up to OpenGL 2.1.

I figured I'd try it out by setting the window hints in GLFW to use the major/minor version of 2 and 0.

Problem is I'm still using #version 330 in my shaders, and it works. However, it would not let me use the hints of GL version 2 when I was leaving on a Core profile (by accident). This seems to indicate that my version choice is doing something, but not what I expect.

I want to restrict myself to 2.1 to see if my application would run, and if it doesn't, then see what I can change to make it work. Problem is I don't have any 2.1 hardware since my computers are all 2015 or later.

Is there a way I can emulate 2.1 (on Windows) somehow and have it crash/die if I try using features it doesn't support? Apparently the hints I'm using are not helping.

opengl
1 Answers

As far as I know the major/minor version flags don't set the version of your OpenGL context but the required feature set. So if you set the flags to 3.3 for example you will usually get a 4.5 or 4.6 context as those version are typically the latest OpenGL versions your GPU supports that is compatible with OpenGL 3.3. Getting a OpenGL 2.1 Core context should be impossible as the defining feature of the core context is that it doesn't support some OpenGL 1.0-2.1 functionality. So this isn't really surprising.

I think your best option here is to use headers that only contain OpenGL 2.1 functions. GLAD for examples allows you to specify which version you want to generate headers for.

user_43593610
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