Force FM/MIDI audio when CD audio is not available

If CD audio is not available (no playlist) but CD playback is specified,
MAKO::play() falls back to FM/MIDI.

Also, on Windows, gray out the "CD Audio" menu item if CD audio is not
available.

src/common.h

@@ -38,6 +38,7 @@ void sys_warning(const char* format, ...);
 extern uint32_t sdl_custom_event_type;
 enum CustomEvent {
 	DEBUGGER_COMMAND,
+	DISABLE_CD_MENU,
 };
 
 // resource.cpp

src/emscripten/mako.cpp

@@ -50,7 +50,7 @@ void MAKO::play_music(int page)
 	stop_music();
 
 	int track = page < 100 ? cd_track[page] : 0;
-	if (track) {
+	if (track && is_cd_available()) {
 		EM_ASM_ARGS({ xsystem35.cdPlayer.play($0, $1); },
 					cd_track[page] + 1, next_loop ? 0 : 1);
 	} else {

src/generic/mako.cpp

@@ -98,7 +98,7 @@ void MAKO::play_music(int page)
 	stop_music();
 
 	int track = page < 100 ? cd_track[page] : 0;
-	if (track) {
+	if (track && is_cd_available()) {
 		if (track < playlist.size() && playlist[track]) {
 #ifdef __ANDROID__
 			// Mix_LoadMUS uses SDL_RWFromFile which requires absolute path on Android

src/win/mako.cpp

@@ -206,6 +206,12 @@ MAKO::MAKO(const Config& config, const GameId& game_id) :
 {
 	if (!config.playlist.empty())
 		load_playlist(config.playlist.c_str());
+	if (!is_cd_available()) {
+		SDL_Event event = {};
+		event.user.type = sdl_custom_event_type;
+		event.user.code = DISABLE_CD_MENU;
+		SDL_PushEvent(&event);
+	}
 
 	amus.open("AMUS.DAT");
 	awav.open("AWAV.DAT");
@@ -283,7 +289,7 @@ void MAKO::play_music(int page)
 	stop_music();
 
 	size_t track = page < 100 ? cd_track[page] : 0;
-	if (track) {
+	if (track && is_cd_available()) {
 		if (track >= playlist.size() || !playlist[track])
 			return;
 		music = new Music(playlist[track], next_loop);

src/win/nact_win.cpp

@@ -173,6 +173,20 @@ void NACT::set_skip_menu_state(bool enabled, bool checked)
 
 bool NACT::handle_platform_event(const SDL_Event& e)
 {
+	if (e.type == sdl_custom_event_type) {
+		switch (e.user.code) {
+		case DISABLE_CD_MENU:
+			{
+				HWND hwnd = get_hwnd(g_window);
+				HMENU hmenu = GetMenu(hwnd);
+				EnableMenuItem(hmenu, ID_OPTION_CD, MF_GRAYED);
+				DrawMenuBar(hwnd);
+			}
+			return true;
+		}
+		return false;
+	}
+
 	if (e.type != SDL_SYSWMEVENT)
 		return false;
 	const SDL_SysWMmsg* msg = e.syswm.msg;