Kill OpenGL 1.x support?

[kintel]

OpenCSG has a bunch of code for supporting OpenGL 1.x (e.g. texture rectangle and non-power-of-two textures).
Is this still needed by anyone, or could we rip out the 1.x support and require OpenGL 2.x+ ?

FYI: OpenSCAD recently deprecated OpenGL 1.x support (openscad/openscad#4550)

[floriankirsch]

Removing PBuffers just seems right. It is very unlikely that some useful hardware would still provide PBuffers, but not frame buffer objects.

At the same time the (anyway unused) code that uses the WGL buffer region extension to save and restore the stencil buffer should be also removed. This should remove all code in OpenCSG that somehow depends directly on GLX or WGL. Note that In the present patch, that buffer region code currently does not compile - and also not the example application.

With the remaining extensions, I am not so convinced. Is there really a benefit? Probably for the texture rectangle path, which is not so well encapsulated in the code. Or - generally, if one could get rid of all extension checks (i.e., remove the dependency on GLEW if possible).

I think I will split your patch into different parts, devoted each to a particular extension, and reconsider.

[kintel]

Let me know if I can assist in splitting up my PR. It is, admittedly a pretty crude PR, mostly since I wanted some feedback before putting more effort into it.