Currently, the glslang check is run every time ninja is invoked,
even with an up-to-date build directory when GLSL shaders haven't
been modified. This is due to glslang not creating any output
file: the _check file never exists so ninja keeps trying to
generate it by running the command.
Unfortunately Meson doesn't support running commands with no
outputs [1]. Create an empty output file to fix this by setting
`capture: true`.
This doesn't work out-of-the-box, because glslang prints messages
to stdout, and provides no way to change this [2]. As a result,
shader errors are not surfaced back to the user - they end up in
the _check file. Workaround this with a thin wrapper which
redirects stdout to stderr when invoking glslang.
[1]: https://github.com/mesonbuild/meson/issues/11506
[2]: https://github.com/KhronosGroup/glslang/pull/4138
Instead of having a C file with strings for each shader, move each
shader into its own file. Use a small POSIX shell script to convert
the files into C strings (can't wait for C23 #embed...).
The benefits from this are:
- Improved readability and syntax highlighting.
- Line numbers in shader compiler errors are easier to make sense of.
- Consistency with the Vulkan renderer.
- Shaders will become more complicated as we add color management
features.
