Sokol: Distinct SOKOL_API macros for libs

[iboB]

This is a Windows-only feature request, as only Windows compilers have special export/import symbols for DLLs.

On Windows it's not possible to put different sokol libs in different DLLs which reference each other, as all libs use the same SOKOL_API_DECL/IMPL export macros.

My particular use case is putting imgui along with sokol_imgui in a separate dll because not all modules use/need imgui. In that dll I want sokol_imgui functions to be dllexport and other sokol functions to be dllimport.

To keep backwards compatibility this can be used:

// sokol_gfx.h
// assuming SOKOL_GFX_API is the macro for sokol_gfx
#if defined(SOKOL_API_DECL)
    #define SOKOL_GFX_API_DECL SOKOL_API_DECL
#endif

#if !defined(SOKOL_GFX_API_DECL) 
// ... 
// same defines and checks as the the ones which used to be for SOKOL_API_DECL

If the proposal is approved, I can whip up PRs for each library

PS I realize that a workaround by creative including is possible: define-include-undef-define-include, but this won't work with C++20 modules, and also it's pretty unpleasant code to write and maintain...

[floooh]

Yeah, this sounds like a good idea. PRs would be welcome.

Somewhat related, I've been thinking for quite a while that this would also make sense for the SOKOL_IMPL define (for the utility headers I'm already doing this). But I'll take care of this at a later time.

[meshula]

Here is the pattern I use in my projects. Demonstrating using USD, each library has its own set of macros - for example:

https://github.com/PixarAnimationStudios/USD/blob/release/pxr/base/tf/api.h

Which pulls in the base definitions:

https://github.com/PixarAnimationStudios/USD/blob/release/pxr/base/arch/export.h

That last file explains pretty clearly the reasoning behind the structure. I've used many different variations over the years, and this feels like the "boss monster final form" version.

[iboB]

@floooh, great!

Do you prefer separate PRs for each lib or one PR for all libs?

[floooh]

Do you prefer separate PRs for each lib or one PR for all libs?

Just put everything into one PR, that's less noisy :)

[floooh]

PS: I've been thinking a little bit about how to handle SOKOL_IMPL in the future, and I like the idea to allow SOKOL_IMPL as a "catch-all" define if one doesn't need per-library defines, but still allow SOKOL_GFX_IMPL, SOKOL_APP_IMPL etc...

Each header would then simply have a:

#if defined(SOKOL_IMPL)
#define SOKOL_GFX_IMPL
#endif

...to make everything work (and that's why I think we should also keep SOKOL_API_DECL and SOKOL_API_IMPL for the future and not just as a backward compatibility hack).

[iboB]

Definitely, yeah.

I was thinking of adding:

#if defined(SOKOL_API_DECL) && !defined(SOKOL_GFX_API_DECL)
// ...

thus a user can use the catch-all export macros and special-case certain libs if they choose

[iboB]

btw, do you mind a draft PR? The problem with it is that you'll get notifications for my commits before the PR is ready to merge

[floooh]

btw, do you mind a draft PR

No problem, do as you like :)

[iboB]

@floooh not sure if you noticed, but my I think PR - #429 - is ready to merge. Do you think it needs anything more?

[floooh]

Yep, I noticed :) I'll try to take care of it within the next few days. I'm trying some sort of "merge day" approach where I try to focus on pending PRs and nothing else, otherwise it's too distracting.