core: Fix BG music not stopping in Samorost (close #963)

[vadosnaprimer]

MovieClip avm1_unload() was already stopping the current stream at https://github.com/ruffle-rs/ruffle/blob/5bebebddbe3c39362ba520cb0c9c28b3cb7f72a3/core/src/display_object/movie_clip.rs#L2924C18-L2924C18 but in Samorost, the BG music that keeps playing after switching SWFs in ruffle is not a stream but a sound.

I don't know how to make it stop only the sound that's currently playing, so here's a "fix" that just stops them all. Technically closes #963 but there may be a neater way.

[Lord-McSweeney]

Thank you for the contribution! Unfortunately this fix is (probably) not the right way to do it. Can you elaborate on what a "sound" is when you stated that the BG music "is not a stream but a sound"? I don't see any StartSound tags or Sound AS code in the SWF.

EDIT: Whoops, nevermind, there's a StartSound that I missed. I think in that case the right way to do it would be to add a list of handles of currently-playing sounds to MovieClipData, add handles to that list whenever the StartSound tag starts a sound (see MovieClip::start_sound_1), then iterate over all of those handles and call context.stop_sounds_with_handle(...) on them when the movie is unloaded.

[vadosnaprimer]

Are there examples of this in the code that I could use? I wouldn't be able to add it from scratch, only by copying an existing approach.

[vadosnaprimer]

@Lord-McSweeney AudioManager::stop_all_sounds() does basically what you describe.

MovieClip::start_sound_1() calls AudioManager::start_sound() which adds to this list:

ruffle/core/src/backend/audio.rs

Lines 346 to 347 in fca17a0

	/// The list of actively playing sounds.
	sounds: Vec<SoundInstance<'gc>>,

AudioManager::stop_all_sounds() clears that list, and then AudioMixer::stop_all_sounds() iterates through AudioMixer::sound_instances and removes each of them from the arena, also clearing it after that.

ruffle/core/src/backend/audio/mixer.rs

Lines 636 to 649 in fca17a0

	pub fn stop_all_sounds(&mut self) {
	let mut sound_instances = self
	.sound_instances
	.lock()
	.expect("Cannot be called reentrant");
	// This is a workaround for a bug in generational-arena:
	// Arena::clear does not properly bump the generational index, allowing for stale references
	// to continue to work (this caused #1315). Arena::remove will force a generation bump.
	// See https://github.com/fitzgen/generational-arena/issues/30
	if let Some((i, _)) = sound_instances.iter().next() {
	sound_instances.remove(i);
	}
	sound_instances.clear();
	}

[Lord-McSweeney]

Yes, except this implementation should only stop sounds that were played in a specific MovieClip, not every sound.

[vadosnaprimer]

I think in that case the right way to do it would be to add a list of handles of currently-playing sounds to MovieClipData, add handles to that list whenever the StartSound tag starts a sound (see MovieClip::start_sound_1), then iterate over all of those handles and call context.stop_sounds_with_handle(...) on them when the movie is unloaded.

If a sound has ended by itself or by the game before unloading the movie, would I also need to remove it from the list of per-clip handles? I was unable to find a place when sounds get removed when they simply end, so I don't know how I'd duplicate the removal regarding my duplicate list.