From c35a2e5f1140ed503b50fb5e917eb0ea3cdb178d Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Sun, 23 Feb 2020 15:41:57 +0100
Subject: [PATCH] - do not hold persistent references to sound channels in SW's
 ambient sound code.

For robustness, channels should always be looked up when needed so that the sound engine is free to do with them as it needs.
---
 source/sw/src/sounds.cpp | 34 +++++++---------------------------
 1 file changed, 7 insertions(+), 27 deletions(-)

diff --git a/source/sw/src/sounds.cpp b/source/sw/src/sounds.cpp
index 009536a7d..22f63d62f 100644
--- a/source/sw/src/sounds.cpp
+++ b/source/sw/src/sounds.cpp
@@ -206,7 +206,6 @@ FRolloffInfo GetRolloff(int basedist)
 struct AmbientSound
 {
     SPRITEp sp;
-    FSoundChan* sndChan;
     int ambIndex;
     int vocIndex;
     int ChanFlags;
@@ -226,12 +225,9 @@ static TArray<AmbientSound*> ambients;
 
 void StopAmbientSound(void)
 {
-    for (auto& amb : ambients)
+    for (auto amb : ambients)
     {
-        if (amb->sndChan)
-        {
-            soundEngine->StopChannel(amb->sndChan);
-        }
+        soundEngine->StopSound(SOURCE_Ambient, amb, -1);
     }
     ambients.Clear();
 }
@@ -271,7 +267,6 @@ void InitAmbient(int num, SPRITEp sp)
     amb->sp = sp;
     amb->ambIndex = num;
     amb->vocIndex = vnum;
-    amb->sndChan = nullptr;
     amb->ChanFlags = 0;
     if (ambarray[num].ambient_flags & v3df_dontpan) amb->ChanFlags |= EChanFlags::FromInt(CHANEXF_DONTPAN);
     if (voc[vnum].voc_flags & vf_loop) amb->ChanFlags |= CHANF_LOOP; 
@@ -354,7 +349,10 @@ static void DoTimedSound(AmbientSound* amb)
     amb->curIndex += synctics;
     if (amb->curIndex >= amb->maxIndex)
     {
-        if (amb->sndChan == nullptr || (amb->sndChan->ChanFlags & CHANF_FORGETTABLE))
+        if (soundEngine->EnumerateChannels([=](FSoundChan* tchan)
+            {
+                return (tchan->Source == amb && !(tchan->ChanFlags & CHANF_FORGETTABLE));
+            }))
         {
             // Check for special case ambient sounds. Since the sound is stopped and doesn't occupy a real channel at this time we can just swap out the sound ID before restarting it.
             int ambid = RandomizeAmbientSpecials(amb->vocIndex);
@@ -397,11 +395,7 @@ static void UpdateAmbients()
         }
         else
         {
-            if (amb->sndChan)
-            {
-                soundEngine->StopChannel(amb->sndChan);
-                amb->sndChan = nullptr;
-            }
+            soundEngine->StopSound(SOURCE_Ambient, amb, -1);
         }
 
     }
@@ -427,7 +421,6 @@ class SWSoundEngine : public SoundEngine
     // client specific parts of the sound engine go in this class.
     void CalcPosVel(int type, const void* source, const float pt[3], int channum, int chanflags, FSoundID chanSound, FVector3* pos, FVector3* vel, FSoundChan* chan) override;
     TArray<uint8_t> ReadSound(int lumpnum) override;
-    void ChannelEnded(FISoundChannel* chan) override;
 
 public:
     SWSoundEngine()
@@ -450,19 +443,6 @@ TArray<uint8_t> SWSoundEngine::ReadSound(int lumpnum)
     return wlump.Read();
 }
 
-void SWSoundEngine::ChannelEnded(FISoundChannel* chan)
-{
-    // if this channel belongs to an ambient sound we have to delete the reference to it.
-    for (auto amb : ambients)
-    {
-        if (amb->sndChan == chan)
-        {
-            amb->sndChan = nullptr;
-        }
-    }
-    SoundEngine::ChannelEnded(chan);
-}
-
 //==========================================================================
 //
 //