especially SDL_VIDEODRIVER is commonly used to use the native Wayland
backend, so I think it's a good idea to keep supporting the old name
instead of forcing users to find out that they now have to add an
underscore..
Not sure how popular SDL_AUDIODRIVER is, but with all the audio backends
that exist on Linux alone I'm sure some people use it to work around
sound issues.
Note: Doing this in the SDL_hints implementation instead of the
call-sites of SDL_GetHint(SDL_HINT_VIDEO_DRIVER) etc ensures that
1. Hint priorities work (env var overriding hint set by application with normal
priority, but not when application used SDL_HINT_OVERRIDE)
2. SDL_ResetHint() (called by user code) respects the fallback
environment variable
My simplification of the conditions for including SDL_main_impl.h
had one problem: I forgot that SDL_main_impl.h must be included
even on Android when SDL_MAIN_USE_CALLBACKS is used, because then a
SDL_main() function that makes sure the callbacks get called is needed,
and that function is implemented in SDL_main_impl.h
But OTOH, even when SDL_MAIN_USE_CALLBACKS is used, SDL_main_impl.h
should not implement a standard `int main(...)` function on Android
(because there the SDL-using native code is compiled as a library and
the entry point is in SDLActivity.java, which calls SDL_main()
in said library).
So the check for platforms that don't have *any* native main function
but just SDL_main() called from the outside should be handled in
SDL_main_impl.h, so both the normal and the callback case can avoid
generating a standard main() in the same way.
To do this, SDL_MAIN_EXPORTED is defined for platforms like Android,
where the real entry point (main() function) is outside of the code
that uses SDL, so
- SDL_main() must be visibly exported with SDL_DECLSPEC, so the outside
code can call it
- SDL_main_impl.h must not implement a "real" main() function
Another small change based on this is defining SDLMAIN_DECLSPEC
at a more general place.
If another platform like Android (where the entry point is somewhere
else entirely, possibly implemented in a different programming language)
turns up, defining SDL_MAIN_NEEDED (so the users main() is renamed
to SDL_main()) and SDL_MAIN_EXPORTED should be all that's needed on the
SDL_main.h side - and if not then at least the implementation is
cleaner and clearer now, IMHO.
fixes#11162
This replaces the internal mutex with a semaphore, so we're only using a
single synchronization primitive to implement this, and cleans up some logic
around wait timeouts.
This now matches the logic of the originally cited work, from BeOS.
Fixes#3639.
(I think.)
