System3: Implement CD availability check

The `Y14,2:` command (`Y20,2:` in Gakuen KING) now returns zero if CD
audio is not available (i.e. playlist is not loaded).

src/emscripten/mako.cpp

@@ -151,6 +151,11 @@ bool MAKO::check_pcm()
 	return EM_ASM_INT({ return xsystem35.audio.pcm_isplaying(0); });
 }
 
+bool MAKO::is_cd_available() const
+{
+	return EM_ASM_INT({ return xsystem35.cdPlayer.hasAudioTrack(); });
+}
+
 extern "C" {
 
 EMSCRIPTEN_KEEPALIVE

src/generic/mako.cpp

@@ -245,3 +245,7 @@ bool MAKO::check_pcm()
 	return Mix_Playing(-1) != 0;
 }
 
+bool MAKO::is_cd_available() const
+{
+	return !playlist.empty();
+}

src/sys/mako.h

@@ -40,6 +40,7 @@ public:
 	bool check_pcm();
 
 	void set_cd_track(int num, int track) { cd_track[num] = track; }
+	bool is_cd_available() const;
 
 #ifdef _WIN32
 	void select_sound(BGMDevice dev);

src/sys/nact_sys3.cpp

@@ -785,8 +785,12 @@ void NACT_Sys3::exec_y(int cmd, int param)
 				text_wait_time = (param - 1) * 1000 / 60;
 			}
 			break;
-		case 14:
-			RND = 1;
+		case 14:  // audio device check
+			if (param == 2) {
+				RND = mako->is_cd_available() ? 1 : 0;
+			} else {
+				RND = 1;
+			}
 			break;
 		case 15:
 			break;
@@ -1402,6 +1406,9 @@ public:
 		TRACE("Y %d,%d:", cmd, param);
 
 		switch (cmd) {
+		case 20:  // audio device check
+			exec_y(14, param);
+			break;
 		case 25:
 			ags->menu.back_color = ags->text.back_color = (param == 1 || param == 2) ? 0 : 1;
 			// text_window = param;

src/win/mako.cpp

@@ -465,6 +465,11 @@ bool MAKO::check_pcm()
 	return !PlaySound(null_wav, NULL, SND_ASYNC | SND_MEMORY | SND_NOSTOP);
 }
 
+bool MAKO::is_cd_available() const
+{
+	return !playlist.empty();
+}
+
 void MAKO::on_mci_notify(const SDL_SysWMmsg* msg)
 {
 	if (!music)