ZDoom

Reporting because right now I cannot address this myself:

A user shader using 'texture2D' to look up a texture fails to compile with Vulkan. Manually changing 'texture2D' to 'texture' makes it work.
Discovered with Freaky Panties.

The problem exists with Apple’s OpenGL too. But with Vulkan it affects all platforms.
I would solve this by adding texture?D functions to our shader header. This solution was already used for noise functions.

I don't think that's a good idea - on Windows 'texrture2D' is still a valid builtin function. So this has to be done platform specific or the text has to be replaced in-place before compilation.

Our shader header is different for OpenGL and Vulkan.
I mentioned Apple’s OpenGL just for the sake of completeness. I have no plans to fix it.
With Vulkan renderer texture2D needs to be handled regardless of platform.

It also needs to get fixed on OpenGL, because if Apple fails here, there's no guarantee that other implementors also remove deprecated functionality.

I tried to fix it as a function override, but that doesn't work. It seems 'texture2d' is a token, not an identifier, so the only way to change it is to patch the shader source.