From 95f4768e462ca5afe4d1619d9659a1c76723fa87 Mon Sep 17 00:00:00 2001
From: James R <justsomejames2@gmail.com>
Date: Fri, 29 Dec 2023 04:32:25 -0800
Subject: [PATCH] Stereo Mode: fix unsequenced track fading at the end

- Starts both stereo and stereo_fade in tandem
- Suspends the tune which is not to be heard
- Swaps suspension when toggling SEQ
- Special handling so fade-out can not be interrupted by
  switching off SEQ
---
 src/menus/transient/sound-test.c | 21 +++++++++++++++++++++
 src/s_sound.c                    | 19 ++++++++++++++-----
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/src/menus/transient/sound-test.c b/src/menus/transient/sound-test.c
index b3a5bcafd..0bd62b307 100644
--- a/src/menus/transient/sound-test.c
+++ b/src/menus/transient/sound-test.c
@@ -80,6 +80,27 @@ static void M_SoundTestSeq(INT32 choice)
 	(void)choice;
 
 	soundtest.autosequence ^= true;
+
+	if (soundtest.playing && S_SoundTestCanSequenceFade())
+	{
+		boolean unfaded = Music_DurationLeft("stereo_fade") > Music_FadeOutDuration("stereo_fade") * TICRATE / 1000;
+
+		// 1) You cannot cancel a fade once it has started
+		// 2) However, if the fade wasn't heard, switching
+		//    over restarts the fade
+		if (!unfaded && Music_Suspended("stereo_fade"))
+		{
+			Music_DelayEnd("stereo_fade", 0);
+			unfaded = true;
+		}
+
+		if (unfaded)
+		{
+			soundtest.tune ^= 1;
+			Music_UnSuspend(S_SoundTestTune(0));
+			Music_Suspend(S_SoundTestTune(1));
+		}
+	}
 }
 
 static void M_SoundTestShf(INT32 choice)
diff --git a/src/s_sound.c b/src/s_sound.c
index 8cc1e7801..66477abec 100644
--- a/src/s_sound.c
+++ b/src/s_sound.c
@@ -1657,6 +1657,12 @@ boolean S_SoundTestCanSequenceFade(void)
 		soundtest.currenttrack == soundtest.current->numtracks-1;
 }
 
+static void S_SoundTestReconfigure(const char *tune)
+{
+	Music_Remap(tune, soundtest.current->name[soundtest.currenttrack]);
+	Music_Play(tune);
+}
+
 void S_SoundTestPlay(void)
 {
 	UINT32 sequencemaxtime = 0;
@@ -1670,9 +1676,8 @@ void S_SoundTestPlay(void)
 	soundtest.playing = true;
 	soundtest.tune = (soundtest.autosequence == true && S_SoundTestCanSequenceFade() == true);
 
-	Music_Remap(soundtest.tune, soundtest.current->name[soundtest.currenttrack]);
-	Music_Loop(soundtest.tune, !soundtest.current->basenoloop[soundtest.currenttrack]);
-	Music_Play(soundtest.tune);
+	S_SoundTestReconfigure("stereo");
+	S_SoundTestReconfigure("stereo_fade");
 
 	// Assuming this song is now actually playing
 	sequencemaxtime = I_GetSongLength();
@@ -1701,8 +1706,12 @@ void S_SoundTestPlay(void)
 		}
 	}
 
-	// ms to TICRATE conversion
-	Music_DelayEnd(S_SoundTestTune(0), (TICRATE*sequencemaxtime)/1000);
+	Music_DelayEnd(
+		S_SoundTestCanSequenceFade() ? "stereo_fade" : "stereo",
+		(TICRATE*sequencemaxtime)/1000 // ms to TICRATE conversion
+	);
+
+	Music_Suspend(S_SoundTestTune(1));
 }
 
 void S_SoundTestStop(void)