Fix resumemusic/musicfadein not working

It seems like they were unfinished. This commit makes them properly
work.

When a track is stopped with stopmusic() or musicfadeout(),
resumemusic() will resume from where the track stopped. musicfadein()
does the same but does it with a gradual fade instead of suddenly
playing it at full volume.

I changed several interfaces around for this. First, setting currentsong
to -1 when music is stopped is handled in the hook callback that gets
called by SDL_mixer whenever the music stops. Otherwise, it'd be
problematic if currentsong was set to -1 when the song starts fading out
instead of when the song actually ends.

Also, music.play() has a few optional arguments now, to reduce the
copying-and-pasting of music code.

Lastly, we have to roll our own tracker of music length by using
SDL_GetPerformanceCounter(), because there's no way to get the music
position if a song fades out. (We could implicitly keep the music
position if we abruptly stopped the song using Mix_PauseMusic(), and
resume it using Mix_ResumeMusic(), but ignoring the fact that those two
functions are also used on the unfocus-pause (which, as it turns out, is
basically a non-issue because the unfocus-pause can use some other
functions), there's no equivalent for fading out, i.e. there's no
"fade out and pause when it fully fades out" function in SDL_mixer.) And
then we have to account for the unfocus-pause in our manual tracker.

Other than that, these commands are now fully functional.

desktop_version/src/KeyPoll.cpp

@@ -1,5 +1,6 @@
 #include "KeyPoll.h"
 #include "Graphics.h"
+#include "Music.h"
 #include <stdio.h>
 #include <string.h>
 #include <utf8/unchecked.h>
@@ -54,6 +55,8 @@ KeyPoll::KeyPoll()
 	}
 
 	linealreadyemptykludge = false;
+
+	pauseStart = 0;
 }
 
 void KeyPoll::enabletextentry()
@@ -254,6 +257,11 @@ void KeyPoll::Poll()
 					}
 				}
 				SDL_DisableScreenSaver();
+				if (Mix_PlayingMusic())
+				{
+					// Correct songStart for how long we were paused
+					music.songStart += SDL_GetPerformanceCounter() - pauseStart;
+				}
 				break;
 			case SDL_WINDOWEVENT_FOCUS_LOST:
 				isActive = false;
@@ -267,6 +275,7 @@ void KeyPoll::Poll()
 					);
 				}
 				SDL_EnableScreenSaver();
+				pauseStart = SDL_GetPerformanceCounter();
 				break;
 
 			/* Mouse Focus */

desktop_version/src/KeyPoll.h

@@ -76,6 +76,8 @@ public:
 
 	bool linealreadyemptykludge;
 
+	Uint64 pauseStart;
+
 private:
 	std::map<SDL_JoystickID, SDL_GameController*> controllers;
 	std::map<SDL_GameControllerButton, bool> buttonmap;

desktop_version/src/Music.cpp

@@ -4,6 +4,8 @@
 #include "BinaryBlob.h"
 #include "Map.h"
 
+void songend();
+
 void musicclass::init()
 {
 	for (size_t i = 0; i < soundTracks.size(); ++i) {
@@ -227,9 +229,20 @@ void musicclass::init()
 	volume = 0.0f;
 	fadeoutqueuesong = -1;
 	dontquickfade = false;
+
+	songStart = 0;
+	songEnd = 0;
+
+	Mix_HookMusicFinished(&songend);
 }
 
-void musicclass::play(int t)
+void songend()
+{
+	music.songEnd = SDL_GetPerformanceCounter();
+	music.currentsong = -1;
+}
+
+void musicclass::play(int t, const double position_sec /*= 0.0*/, const int fadein_ms /*= 3000*/)
 {
 	t = (t % 16);
 
@@ -250,9 +263,9 @@ void musicclass::play(int t)
 			if (currentsong == 0 || currentsong == 7 || (!map.custommode && (currentsong == 16 || currentsong == 23)))
 			{
 				// Level Complete theme, no fade in or repeat
-				if(Mix_FadeInMusic(musicTracks[t].m_music, 0, 0)==-1)
+				if(Mix_FadeInMusicPos(musicTracks[t].m_music, 0, 0, position_sec)==-1)
 				{
-					printf("Mix_PlayMusic: %s\n", Mix_GetError());
+					printf("Mix_FadeInMusicPos: %s\n", Mix_GetError());
 				}
 			}
 			else
@@ -266,11 +279,13 @@ void musicclass::play(int t)
 					else
 						dontquickfade = false;
 				}
-				else if(Mix_FadeInMusic(musicTracks[t].m_music, -1, 3000)==-1)
+				else if(Mix_FadeInMusicPos(musicTracks[t].m_music, -1, fadein_ms, position_sec)==-1)
 				{
-					printf("Mix_FadeInMusic: %s\n", Mix_GetError());
+					printf("Mix_FadeInMusicPos: %s\n", Mix_GetError());
 				}
 			}
+
+			songStart = SDL_GetPerformanceCounter();
 		}
 		else
 		{
@@ -279,10 +294,25 @@ void musicclass::play(int t)
 	}
 }
 
+void musicclass::resume(const int fadein_ms /*= 0*/)
+{
+	const double offset = static_cast<double>(songEnd - songStart);
+	const double frequency = static_cast<double>(SDL_GetPerformanceFrequency());
+
+	const double position_sec = offset / frequency;
+
+	play(resumesong, position_sec, fadein_ms);
+}
+
+void musicclass::fadein()
+{
+	resume(3000); // 3000 ms fadein
+}
+
 void musicclass::haltdasmusik()
 {
 	Mix_HaltMusic();
-	currentsong = -1;
+	resumesong = currentsong;
 }
 
 void musicclass::silencedasmusik()
@@ -300,7 +330,7 @@ void musicclass::fadeMusicVolumeIn(int ms)
 void musicclass::fadeout()
 {
 	Mix_FadeOutMusic(2000);
-	currentsong = -1;
+	resumesong = currentsong;
 }
 
 void musicclass::processmusicfadein()

desktop_version/src/Music.h

@@ -13,11 +13,13 @@ class musicclass
 public:
 	void init();
 
-	void play(int t);
+	void play(int t, const double position_sec = 0.0, const int fadein_ms = 3000);
+	void resume(const int fadein_ms = 0);
 	void haltdasmusik();
 	void silencedasmusik();
 	void fadeMusicVolumeIn(int ms);
 	void fadeout();
+	void fadein();
 	void processmusicfadein();
 	void processmusic();
 	void niceplay(int t);
@@ -53,6 +55,9 @@ public:
 	bool usingmmmmmm;
 
 	binaryBlob musicReadBlob;
+
+	Uint64 songStart;
+	Uint64 songEnd;
 };
 
 extern musicclass music;

desktop_version/src/Script.cpp

@@ -260,7 +260,7 @@ void scriptclass::run()
 			}
 			if (words[0] == "resumemusic")
 			{
-				music.play(music.resumesong);
+				music.resume();
 			}
 			if (words[0] == "musicfadeout")
 			{
@@ -269,8 +269,7 @@ void scriptclass::run()
 			}
 			if (words[0] == "musicfadein")
 			{
-				music.musicfadein = 90;
-				//if(!game.muted) music.fadeMusicVolumeIn(3000);
+				music.fadein();
 			}
 			if (words[0] == "trinketscriptmusic")
 			{