C++20 Modules Support

[tsarn]

Hi! Thanks for the project :) I've made a PR adding support for C++20 modules. In this implementation, module's source is #ifdefed inside the webgpu.hpp file. The webgpu.cppm module file simply defines WEBGPU_CPP_MODULE and includes webgpu.hpp.

This is how the header looks normally:

#include <webgpu.h>
// other includes

namespace wgpu {
// interface
#ifdef WEBGPU_CPP_IMPLEMENTATION
// implementation
#endif
}

And this is how the header looks when the WEBGPU_CPP_MODULE is defined. This is intended to be compiled as a standalone module unit:

module;

#include <webgpu.h>
// other includes

export module webgpu;

export namespace wgpu {
// interface
// implementation
}

[eliemichel]

This looks nice! Is there a way to avoid the presence of a .cppm file? Is this a standard extension (not very used to modules yet)? And could you provide a minimal usage example (e.g., just creating a wgpu instance)?

[eliemichel]

I finally found the time to test this, and run into issues on MSVC:

error C7579: the module declaration following a global module fragment cannot be produced by macro expansion or header inclusion

I think we'll need to reorganize this a little bit, but the overall idea is good!

Maybe a solution would be to have the webgpu.cppm file look like this:

module;

#define WEBGPU_CPP_MODULE

#define WEBGPU_CPP_GLOBAL_MODULE_FRAGMENT_ONLY
#include "webgpu.hpp"
#undef WEBGPU_CPP_GLOBAL_MODULE_FRAGMENT_ONLY

export module webgpu;

#define WEBGPU_CPP_NO_GLOBAL_MODULE_FRAGMENT
#include "webgpu.hpp"
#undef WEBGPU_CPP_NO_GLOBAL_MODULE_FRAGMENT

edit: Also we should make sure to enclose the #include <webgpu/webgup.h in a export { } block to re-export the raw C API.

[tsarn]

Ah, I didn't know this doesn't work like this on MSVC. I unfortunately don't have time at the moment to look at how to fix that :/