Fix audio leaking in builtin SDL_mixer

Author: caiiiycuk

src/library_sdl.js

@@ -2817,6 +2817,7 @@ var LibrarySDL = {
   Mix_ReserveChannels: (num) => {
     SDL.channelMinimumNumber = num;
   },
+  Mix_PlayChannelTimed__deps: ['Mix_HaltChannel'],
   Mix_PlayChannelTimed__proxy: 'sync',
   Mix_PlayChannelTimed: (channel, id, loops, ticks) => {
     // TODO: handle fixed amount of N loops. Currently loops either 0 or infinite times.
@@ -2863,6 +2864,9 @@ var LibrarySDL = {
       if (channelInfo.audio == this) { channelInfo.audio.paused = true; channelInfo.audio = null; }
       if (SDL.channelFinished)  {{{ makeDynCall('vi', 'SDL.channelFinished') }}}(channel);
     }
+    if (channelInfo.audio) {
+      _Mix_HaltChannel(channel);
+    }
     channelInfo.audio = audio;
     // TODO: handle N loops. Behavior matches Mix_PlayMusic
     audio.loop = loops != 0;

test/browser/test_sdl_audio_mix_channels_halt.cpp

@@ -0,0 +1,44 @@
+#include <SDL/SDL_mixer.h>
+#include <chrono>
+#include <emscripten.h>
+
+using namespace std::chrono;
+
+Mix_Chunk* chunk = nullptr;
+uint64_t started = duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();
+uint64_t lastRun = 0;
+
+void loop() {
+    uint64_t now = duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();
+    if (now - lastRun > 300) {
+        Mix_PlayChannel(0, chunk, -1);
+        lastRun = now;
+    }
+    if (now - started > 3000) {
+        emscripten_force_exit(0);
+    }
+}
+
+int main(int argc, char** argv) {
+    if ((Mix_Init(MIX_INIT_OGG) & MIX_INIT_OGG) != MIX_INIT_OGG) {
+      printf("ERR! Mix_Init: Failed to init with required flags support!\n");
+      printf("ERR! Mix_Init: %s\n", Mix_GetError());
+      return -1;
+    }
+
+    if (Mix_OpenAudio(MIX_DEFAULT_FREQUENCY, MIX_DEFAULT_FORMAT, 1, 1024) == -1) {
+      printf("ERR! Mix_OpenAudio: %s\n", Mix_GetError());
+      return -1;
+    }
+
+    Mix_AllocateChannels(1);
+    chunk = Mix_LoadWAV("/the_entertainer.ogg");
+    if (!chunk) {
+      printf("ERR! Mix_LoadWAV: %s\n", Mix_GetError());
+      return -1;
+    }
+
+    printf("The sound should reset to start every 300ms, if you hear overapplied music then the test has failed.\n");
+    emscripten_set_main_loop(loop, 0, 0);
+    return 0;
+}

test/test_interactive.py

@@ -82,6 +82,15 @@ def test_sdl_audio_mix_channels(self, args):
 
     self.btest_exit('test_sdl_audio_mix_channels.c', args=['-O2', '--minify=0', '--preload-file', 'sound.ogg'] + args)
 
+  @parameterized({
+    '': ([],),
+    'wasmfs': (['-sWASMFS'],),
+  })
+  def test_sdl_audio_mix_channels_halt(self, args):
+    shutil.copyfile(test_file('sounds/the_entertainer.ogg'), self.in_dir('the_entertainer.ogg'))
+
+    self.btest_exit('test_sdl_audio_mix_channels_halt.cpp', args=['-O2', '--minify=0', '--preload-file', 'the_entertainer.ogg'] + args)
+
   @parameterized({
     '': ([],),
     'wasmfs': (['-sWASMFS'],),