nCine/Graphics/RHI/LegacyGL/LegacyGlApi.h file

The OpenGL 1.x entry points the fixed-function GL backend draws with.

Separate from nCine/CommonHeaders.h, which sets up the shader GL backend: this one wants the legacy headers and nothing else. Three hosts matter today - MorphOS, where OpenGL is TinyGL and the entry points are the SDK's inline macros; AmigaOS 4, where it is MiniGL on top of Warp3D; and a desktop GL, which is where both of those are developed and looked at.

They do not agree on how much of OpenGL exists, so what is optional is stated here rather than assumed: RHI_LEGACYGL_HAS_FBO says whether the framebuffer-object entry points can even be CALLED (MiniGL exports none, so a call would not link), and where they can, the backend still probes at run time whether they work.