help wanted adding pthread support to sdl2_mixer

[db-tech]

Hi,

I wanted to add pthread support to the sdl2_mixer port just like sdl2_ttf and sdl2_image have it.
I am relatively new to python and emscripten so I got a question.

how is this variants being used, is there some documentation somewhere ?
in sdl2_mixer for example are two variants:

variants = {
  'sdl2_mixer_mp3': {'SDL2_MIXER_FORMATS': ["mp3"]},
  'sdl2_mixer_none': {'SDL2_MIXER_FORMATS': []},
}

where is the decision being made that sdl2_mixer_mp3 is being used ?

in the __init__.py I can see that there is the port_variants variable where the variants gets collected into.
And in the embuilder.py, the function get_port_variant is using it.

But I still don't understand it fully... what is calling "get_port_variant" ? would a name like "sdl2_image-png-mt" or equivalent then sdl2_mixer_mp3-mt then being build somewhere ?

[db-tech]

So, I just went ahead and created a PR (#23094).
Although the questions are still open, the changes work for me, so It might not be totally wrong :-)

[sbc100]

What is the motivation here? Does SDL2_mixer actually use threads?

[db-tech]

To be honest, I don't know. I can not really see much thread related stuff in the SDL2_mixer repo.
Without the changes I get a log of errors like:

AssertionError: attempt to lock the cache while a parent process is holding the lock (sysroot/lib/wasm32-emscripten/libSDL2.a)

So It might be a dependency problem ? Maybe because mixer depends on another SDL2 version then the others now ? Not sure

[sbc100]

Ah yes, if it solves the dependency issue then this looks like the only/right fix

[sbc100]

Please mentions the issue it fixed in the PR description.

[lsl330]

Please mentions the issue it fixed in the PR description.

will sdl2_mixer format variants support "opus"?i think the opus format is friendly for web.i have build the sdl_mixer support opus for other platform,but when i build with -s SDL2_MIXER_FORMATS='["mp3","ogg","opus"]'
i found it's not useful。
when i search the documents，
Formats to support in SDL2_mixer. Valid values: ogg, mp3, mod, mid

so will sdl2_mixer format variants support "opus"?
thanks!

[sbc100]

If you would like to support opus that would mean adding an opus port and then adding opus to the list of available formats in ports/sdl2_mixer.py. If you are doing to be using opus support maybe you could send a PR to add that?