From 8da99fc5d1820ffb70180167998321d3bc3ade68 Mon Sep 17 00:00:00 2001
From: Michael Martin <mcmartin@gmail.com>
Date: Sun, 27 Sep 2020 18:01:14 -0700
Subject: [PATCH] Fix the ZFP dialog desync bug introduced post 0.7.

The core issue is that the sound-advancement callbacks (used only
for altering the ZFP dialog locations) were altered to be launched
asynchronously from the main thread. This meant that new dialog
could be detected before the waiting callbacks had run.

This patch moves audio callbacks back into the audio decoding thread
and protects them with the speech-channel mutex. This should
guarantee that cur_sub_chunk only appears as a value when consulting
the current subtitles after the callback has run completely.

Logic has also been added to CheckSubtitles to raise a warning in
the logs if the values get out of sync.
---
 sc2/src/libs/sound/trackplayer.c |  4 +++-
 sc2/src/uqm/comm.c               | 21 +++++++++++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/sc2/src/libs/sound/trackplayer.c b/sc2/src/libs/sound/trackplayer.c
index edff1943b..8068fc388 100644
--- a/sc2/src/libs/sound/trackplayer.c
+++ b/sc2/src/libs/sound/trackplayer.c
@@ -198,10 +198,12 @@ StopTrack (void)
 static void
 DoTrackTag (TFB_SoundChunk *chunk)
 {
+	LockMutex (soundSource[SPEECH_SOURCE].stream_mutex);
 	if (chunk->callback)
-		Callback_add(chunk->callback, 0);
+		chunk->callback(0);
 	
 	cur_sub_chunk = chunk;
+	UnlockMutex (soundSource[SPEECH_SOURCE].stream_mutex);
 }
 
 // This func is called by PlayStream() when stream is about
diff --git a/sc2/src/uqm/comm.c b/sc2/src/uqm/comm.c
index 6336de8a9..ff2818c43 100644
--- a/sc2/src/uqm/comm.c
+++ b/sc2/src/uqm/comm.c
@@ -532,7 +532,7 @@ UpdateAnimations (bool paused)
 	BatchGraphics ();
 	// Advance and draw ambient, transit and talk animations
 	change = ProcessCommAnimations (clear_subtitles, paused);
-	if (change)
+	if (change || clear_subtitles)
 		RedrawSubtitles ();
 	UnbatchGraphics ();
 	clear_subtitles = FALSE;
@@ -1608,15 +1608,28 @@ static void
 CheckSubtitles (void)
 {
 	const UNICODE *pStr;
+	POINT baseline;
+	TEXT_ALIGN align;
 
 	pStr = GetTrackSubtitle ();
+	baseline = CommData.AlienTextBaseline;
+	align = CommData.AlienTextAlign;
 
-	if (pStr != SubtitleText.pStr)
+	if (pStr != SubtitleText.pStr ||
+			SubtitleText.baseline.x != baseline.x ||
+			SubtitleText.baseline.y != baseline.y ||
+			SubtitleText.align != align)
 	{	// Subtitles changed
 		clear_subtitles = TRUE;
 		// Baseline may be updated by the ZFP
-		SubtitleText.baseline = CommData.AlienTextBaseline;
-		SubtitleText.align = CommData.AlienTextAlign;
+		SubtitleText.baseline = baseline;
+		SubtitleText.align = align;
+		// Make a note in the logs if the update was multiframe
+		if (SubtitleText.pStr == pStr)
+		{
+			log_add (log_Warning, "Dialog text and location changed out of sync");
+		}
+
 		SubtitleText.pStr = pStr;
 		// may have been cleared too
 		if (pStr)