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dummyaudio: single-threaded Emscripten support. 

On Emscripten without pthreads, this would fail because SDL can't spin the
audio device thread, and the dummy backend didn't manage a thread itself.

With this patch, we use setInterval to fire the usual audio thread iterators
between iterations of the Emscripten mainloop on the main thread.

Fixes #10573.
This commit is contained in:
Ryan C. Gordon 2024-08-25 15:01:33 -04:00
parent 845212388e
commit d118af53a1
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GPG Key ID: FA148B892AB48044
1 changed files with 36 additions and 0 deletions
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36
src/audio/dummy/SDL_dummyaudio.c
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@ -25,6 +25,10 @@
#include "../SDL_sysaudio.h"
#include "SDL_dummyaudio.h"
#if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
#include <emscripten/emscripten.h>
#endif
static int DUMMYAUDIO_WaitDevice(SDL_AudioDevice *device)
{
SDL_Delay(device->hidden->io_delay);
@ -54,12 +58,30 @@ static int DUMMYAUDIO_OpenDevice(SDL_AudioDevice *device)
device->hidden->io_delay = (Uint32)SDL_round(device->hidden->io_delay * scale);
}
}
// on Emscripten without threads, we just fire a repeating timer to consume audio.
#if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
MAIN_THREAD_EM_ASM({
var a = Module['SDL3'].dummy_audio;
if (a.timers[$0] !== undefined) { clearInterval(a.timers[$0]); }
a.timers[$0] = setInterval(function() { dynCall('vi', $3, [$4]); }, ($1 / $2) * 1000);
}, device->recording ? 1 : 0, device->sample_frames, device->spec.freq, device->recording ? SDL_RecordingAudioThreadIterate : SDL_PlaybackAudioThreadIterate, device);
#endif
return 0; // we're good; don't change reported device format.
}
static void DUMMYAUDIO_CloseDevice(SDL_AudioDevice *device)
{
if (device->hidden) {
// on Emscripten without threads, we just fire a repeating timer to consume audio.
#if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
MAIN_THREAD_EM_ASM({
var a = Module['SDL3'].dummy_audio;
if (a.timers[$0] !== undefined) { clearInterval(a.timers[$0]); }
a.timers[$0] = undefined;
}, device->recording ? 1 : 0);
#endif
SDL_free(device->hidden->mixbuf);
SDL_free(device->hidden);
device->hidden = NULL;
@ -91,6 +113,20 @@ static bool DUMMYAUDIO_Init(SDL_AudioDriverImpl *impl)
impl->OnlyHasDefaultRecordingDevice = true;
impl->HasRecordingSupport = true;
// on Emscripten without threads, we just fire a repeating timer to consume audio.
#if defined(SDL_PLATFORM_EMSCRIPTEN) && !defined(__EMSCRIPTEN_PTHREADS__)
MAIN_THREAD_EM_ASM({
if (typeof(Module['SDL3']) === 'undefined') {
Module['SDL3'] = {};
}
Module['SDL3'].dummy_audio = {};
Module['SDL3'].dummy_audio.timers = [];
Module['SDL3'].dummy_audio.timers[0] = undefined;
Module['SDL3'].dummy_audio.timers[1] = undefined;
});
impl->ProvidesOwnCallbackThread = true;
#endif
return true;
}