Add build time flag to choose whether to enable ADL MIDI support

Since ADL MIDI is not packaged on some distributions, default the option
to off.

SConstruct

@@ -1160,6 +1160,22 @@ struct d_screenshot
 		successflags = self.pkgconfig.merge(context, self.msgprefix, self.user_settings, 'libpng', 'libpng', _guess_flags)
 		return self._soft_check_system_library(context, header=_header, main=_main, lib='png', text=_text, successflags=successflags)
 
+	@_custom_test
+	def _check_user_settings_adldmidi(self,context):
+		user_settings = self.user_settings
+		adlmidi = user_settings.adlmidi
+		if adlmidi == 'none':
+			adlmidi_load_type = 'disabled'
+		elif adlmidi == 'runtime':
+			adlmidi_load_type = 'load dynamically'
+		else:
+			return
+		context.Result('%s: checking how to handle ADL MIDI...%s' % (self.msgprefix, adlmidi_load_type))
+		Define = context.sconf.Define
+		enable_adlmidi = int(adlmidi != 'none')
+		user_settings._enable_adlmidi = enable_adlmidi
+		Define('DXX_USE_ADLMIDI', enable_adlmidi)
+
 	@_custom_test
 	def _check_user_settings_screenshot(self,context):
 		user_settings = self.user_settings
@@ -3440,6 +3456,8 @@ class DXXCommon(LazyObjectConstructor):
 			if self.raspberrypi == 'yes':
 				return 'brcmEGL'
 			return self.default_EGL_LIB
+		def need_dynamic_library_load(self):
+			return self.adlmidi == 'runtime'
 
 		def __default_DATA_DIR(self):
 			platform_settings_type = self._program.get_platform_settings_type(self.host_platform)
@@ -3634,6 +3652,7 @@ class DXXCommon(LazyObjectConstructor):
 				'variable': EnumVariable,
 				'arguments': (
 					('host_endian', None, 'endianness of host platform', {'allowed_values' : ('little', 'big')}),
+					('adlmidi', 'none', 'include ADL MIDI support (none: disabled; runtime: dynamically load at runtime)', {'allowed_values' : ('none', 'runtime')}),
 					('screenshot', 'png', 'screenshot file format', {'allowed_values' : ('none', 'legacy', 'png')}),
 				),
 			},
@@ -4254,7 +4273,6 @@ class DXXArchive(DXXCommon):
 'common/3d/points.cpp',
 'common/3d/rod.cpp',
 'common/3d/setup.cpp',
-'common/music/adlmidi_dynamic.cpp',
 'common/arch/sdl/event.cpp',
 'common/arch/sdl/joy.cpp',
 'common/arch/sdl/key.cpp',
@@ -4277,13 +4295,19 @@ class DXXArchive(DXXCommon):
 'common/misc/vgrphys.cpp',
 'common/misc/vgwphys.cpp',
 )), \
+		__get_objects_use_adlmidi=DXXCommon.create_lazy_object_getter((
+'common/music/adlmidi_dynamic.cpp',
+)),
 		__get_objects_use_sdl1=DXXCommon.create_lazy_object_getter((
 'common/arch/sdl/rbaudio.cpp',
 ))
 		):
 		value = list(__get_objects_common(self))
 		extend = value.extend
-		if not self.user_settings.sdl2:
+		user_settings = self.user_settings
+		if user_settings._enable_adlmidi:
+			extend(__get_objects_use_adlmidi(self))
+		if not user_settings.sdl2:
 			extend(__get_objects_use_sdl1(self))
 		extend(self.platform_settings.get_platform_objects())
 		return value
@@ -4642,6 +4666,11 @@ class DXXProgram(DXXCommon):
 			DXXCommon.LinuxPlatformSettings.__init__(self,program,user_settings)
 			if user_settings.sharepath and user_settings.sharepath[-1] != '/':
 				user_settings.sharepath += '/'
+		def adjust_environment(self,program,env):
+			DXXCommon.LinuxPlatformSettings.adjust_environment(self,program,env)
+			user_settings = self.user_settings
+			if user_settings.need_dynamic_library_load():
+				env.Append(LIBS = ['dl'])
 
 	def get_objects_common(self,
 		__get_objects_common=__get_objects_common,
@@ -4702,7 +4731,7 @@ class DXXProgram(DXXCommon):
 				('__STDC_FORMAT_MACROS',),
 			],
 			CPPPATH = [os.path.join(self.srcdir, 'main')],
-			LIBS = ['m', 'dl'],
+			LIBS = ['m'],
 		)
 
 	def register_program(self):

common/arch/sdl/digi_mixer_music.cpp

@@ -91,9 +91,10 @@ class current_music_t
 }
 
 static current_music_t current_music;
-static ADL_MIDIPlayer_t current_adlmidi;
 static std::vector<uint8_t> current_music_hndlbuf;
 
+#if DXX_USE_ADLMIDI
+static ADL_MIDIPlayer_t current_adlmidi;
 static ADL_MIDIPlayer *get_adlmidi()
 {
 	ADL_MIDIPlayer *adlmidi = current_adlmidi.get();
@@ -114,10 +115,15 @@ static ADL_MIDIPlayer *get_adlmidi()
 	return adlmidi;
 }
 
+static void mix_adlmidi(void *udata, Uint8 *stream, int len);
+#endif
+
 enum class CurrentMusicType
 {
 	None,
+#if DXX_USE_ADLMIDI
 	ADLMIDI,
+#endif
 	SDLMixer,
 };
 
@@ -126,9 +132,6 @@ static CurrentMusicType current_music_type = CurrentMusicType::None;
 static CurrentMusicType load_mus_data(const uint8_t *data, size_t size);
 static CurrentMusicType load_mus_file(const char *filename);
 
-static void mix_adlmidi(void *udata, Uint8 *stream, int len);
-
-
 /*
  *  Plays a music file from an absolute path or a relative path
  */
@@ -139,8 +142,6 @@ int mix_play_file(const char *filename, int loop, void (*hook_finished_track)())
 	const char *fptr;
 	unsigned int bufsize = 0;
 
-	// fprintf(stderr, "Load music: %s\n", filename);
-
 	mix_free_music();	// stop and free what we're already playing, if anything
 
 	fptr = strrchr(filename, '.');
@@ -198,6 +199,7 @@ int mix_play_file(const char *filename, int loop, void (*hook_finished_track)())
 	switch (current_music_type)
 	{
 
+#if DXX_USE_ADLMIDI
 	case CurrentMusicType::ADLMIDI:
 	{
 		ADL_MIDIPlayer *adlmidi = get_adlmidi();
@@ -206,6 +208,7 @@ int mix_play_file(const char *filename, int loop, void (*hook_finished_track)())
 		Mix_HookMusicFinished(hook_finished_track ? hook_finished_track : mix_free_music);
 		return 1;
 	}
+#endif
 
 	case CurrentMusicType::SDLMixer:
 	{
@@ -229,7 +232,15 @@ int mix_play_file(const char *filename, int loop, void (*hook_finished_track)())
 void mix_free_music()
 {
 	Mix_HaltMusic();
+#if DXX_USE_ADLMIDI
+	/* Only ADLMIDI can set a hook, so if ADLMIDI is compiled out, there is no
+	 * need to clear the hook.
+	 *
+	 * When ADLMIDI is supported, clear unconditionally, instead of checking
+	 * whether the music type requires it.
+	 */
 	Mix_HookMusic(nullptr, nullptr);
+#endif
 	current_music.reset();
 	current_music_hndlbuf.clear();
 	current_music_type = CurrentMusicType::None;
@@ -268,14 +279,15 @@ void mix_pause_resume_music()
 static CurrentMusicType load_mus_data(const uint8_t *data, size_t size)
 {
 	CurrentMusicType type = CurrentMusicType::None;
+#if DXX_USE_ADLMIDI
 	ADL_MIDIPlayer *adlmidi = get_adlmidi();
-	SDL_RWops *rw = NULL;
 
 	if (adlmidi && adl_openData(adlmidi, data, size) == 0)
 		type = CurrentMusicType::ADLMIDI;
 	else
+#endif
 	{
-		rw = SDL_RWFromConstMem(data, size);
+		const auto rw = SDL_RWFromConstMem(data, size);
 		current_music.reset(Mix_LoadMUS_RW(rw DXX_SDL_MIXER_Mix_LoadMUS_MANAGE_RWOPS) DXX_SDL_MIXER_Mix_LoadMUS_PASS_RWOPS(rw));
 		if (current_music)
 			type = CurrentMusicType::SDLMixer;
@@ -287,11 +299,13 @@ static CurrentMusicType load_mus_data(const uint8_t *data, size_t size)
 static CurrentMusicType load_mus_file(const char *filename)
 {
 	CurrentMusicType type = CurrentMusicType::None;
+#if DXX_USE_ADLMIDI
 	ADL_MIDIPlayer *adlmidi = get_adlmidi();
 
 	if (adlmidi && adl_openFile(adlmidi, filename) == 0)
 		type = CurrentMusicType::ADLMIDI;
 	else
+#endif
 	{
 		current_music.reset(Mix_LoadMUS(filename));
 		if (current_music)
@@ -301,6 +315,7 @@ static CurrentMusicType load_mus_file(const char *filename)
 	return type;
 }
 
+#if DXX_USE_ADLMIDI
 static int16_t sat16(int32_t x)
 {
 	x = (x < INT16_MIN) ? INT16_MIN : x;
@@ -323,5 +338,6 @@ static void mix_adlmidi(void *, Uint8 *stream, int len)
 	const auto amplify = [](int16_t i) { return sat16(2 * i); };
 	std::transform(samples, samples + sampleCount, samples, amplify);
 }
+#endif
 
 }

common/include/adlmidi_dynamic.h

@@ -10,7 +10,9 @@
 
 #include <memory>
 #include <stdint.h>
+#include "dxxsconf.h"
 
+#if DXX_USE_ADLMIDI
 struct ADL_MIDIPlayer;
 
 enum ADLMIDI_SampleType
@@ -71,3 +73,4 @@ struct ADLMIDI_delete
 };
 
 typedef std::unique_ptr<ADL_MIDIPlayer, ADLMIDI_delete> ADL_MIDIPlayer_t;
+#endif