Support formats option in sdl2 mixer (#24158)

This PR adds `handle_options` function in the SDL2_mixer port so one can
build SDL2_mixer with specific formats with embuilder, such as

```
embuilder build sdl2_mixer:formats:mid,ogg,mp3
```

I found this syntax was added in
#21345, but it was
only applied to SDL2_image.

Author: ryanking13

test/test_other.py

@@ -2469,6 +2469,7 @@ def test_sdl_get_key_name(self):
   def test_sdl2_mixer_wav(self):
     self.emcc(test_file('browser/test_sdl2_mixer_wav.c'), ['-sUSE_SDL_MIXER=2'], output_filename='a.out.js')
     self.emcc(test_file('browser/test_sdl2_mixer_wav.c'), ['--use-port=sdl2_mixer'], output_filename='a.out.js')
+    self.emcc(test_file('browser/test_sdl2_mixer_wav.c'), ['--use-port=sdl2_mixer:formats=ogg'], output_filename='a.out.js')
 
   def test_sdl2_linkable(self):
     # Ensure that SDL2 can be built with LINKABLE.  This implies there are no undefined

tools/ports/sdl2_image.py

@@ -34,7 +34,7 @@ def needed(settings):
 
 
 def get_formats(settings):
-  return set(settings.SDL2_IMAGE_FORMATS).union(opts['formats'])
+  return opts['formats'].union(settings.SDL2_IMAGE_FORMATS)
 
 
 def get_lib_name(settings):

tools/ports/sdl2_mixer.py

@@ -4,6 +4,7 @@
 # found in the LICENSE file.
 
 import os
+from typing import Dict, Set
 
 TAG = 'release-2.8.0'
 HASH = '494ccd74540f74e717f7e4f1dc7f96398c0f4b1883ab00c4a76b0c7239bd2c185cb4358a35ef47819c49e7c14dac7c37b98a29c7b5237478121571f5e7ac4dfc'
@@ -16,14 +17,28 @@
   'sdl2_mixer-none-mt': {'SDL2_MIXER_FORMATS': [], 'PTHREADS': 1},
 }
 
+OPTIONS = {
+  'formats': 'A comma separated list of formats (ex: --use-port=sdl2_mixer:formats=ogg,mp3)'
+}
+
+SUPPORTED_FORMATS = {'ogg', 'mp3', 'mod', 'mid'}
+
+# user options (from --use-port)
+opts: Dict[str, Set] = {
+  'formats': set()
+}
+
 
 def needed(settings):
   return settings.USE_SDL_MIXER == 2
 
 
+def get_formats(settings):
+  return opts['formats'].union(settings.SDL2_MIXER_FORMATS)
+
+
 def get_lib_name(settings):
-  settings.SDL2_MIXER_FORMATS.sort()
-  formats = '-'.join(settings.SDL2_MIXER_FORMATS)
+  formats = '-'.join(sorted(get_formats(settings)))
 
   libname = 'libSDL2_mixer'
   if formats != '':
@@ -41,30 +56,33 @@ def get(ports, settings, shared):
 
   def create(final):
     source_path = ports.get_dir('sdl2_mixer', 'SDL_mixer-' + TAG)
+
+    formats = get_formats(settings)
+
     flags = [
       '-sUSE_SDL=2',
       '-DMUSIC_WAV',
     ]
 
-    if "ogg" in settings.SDL2_MIXER_FORMATS:
+    if "ogg" in formats:
       flags += [
         '-sUSE_VORBIS',
         '-DMUSIC_OGG',
       ]
 
-    if "mp3" in settings.SDL2_MIXER_FORMATS:
+    if "mp3" in formats:
       flags += [
         '-sUSE_MPG123',
         '-DMUSIC_MP3_MPG123',
       ]
 
-    if "mod" in settings.SDL2_MIXER_FORMATS:
+    if "mod" in formats:
       flags += [
         '-sUSE_MODPLUG',
         '-DMUSIC_MOD_MODPLUG',
       ]
 
-    if "mid" in settings.SDL2_MIXER_FORMATS:
+    if "mid" in formats:
       flags += [
         '-DMUSIC_MID_TIMIDITY',
       ]
@@ -107,16 +125,27 @@ def clear(ports, settings, shared):
 
 def process_dependencies(settings):
   settings.USE_SDL = 2
-  if "ogg" in settings.SDL2_MIXER_FORMATS:
+  formats = get_formats(settings)
+  if "ogg" in formats:
     deps.append('vorbis')
     settings.USE_VORBIS = 1
-  if "mp3" in settings.SDL2_MIXER_FORMATS:
+  if "mp3" in formats:
     deps.append('mpg123')
     settings.USE_MPG123 = 1
-  if "mod" in settings.SDL2_MIXER_FORMATS:
+  if "mod" in formats:
     deps.append('libmodplug')
     settings.USE_MODPLUG = 1
 
 
+def handle_options(options, error_handler):
+  formats = options['formats'].split(',')
+  for format in formats:
+    format = format.lower().strip()
+    if format not in SUPPORTED_FORMATS:
+      error_handler(f'{format} is not a supported format')
+    else:
+      opts['formats'].add(format)
+
+
 def show():
   return 'sdl2_mixer (-sUSE_SDL_MIXER=2 or --use-port=sdl2_mixer; zlib license)'