From 444418e8c183af6536c567238d610e04cd9ebd12 Mon Sep 17 00:00:00 2001
From: Paul <baconpaul@users.noreply.github.com>
Date: Sun, 15 Sep 2024 14:06:47 -0400
Subject: [PATCH] Fix a problem with optimization  5bcfdb5400 (#1330)

---
 src/engine/group.cpp | 46 +++++++++++++++++++++++++-------------------
 src/engine/group.h   |  2 ++
 2 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/src/engine/group.cpp b/src/engine/group.cpp
index ce39b391..fef52710 100644
--- a/src/engine/group.cpp
+++ b/src/engine/group.cpp
@@ -179,11 +179,16 @@ template <bool OS> void Group::processWithOS(scxt::engine::Engine &e)
     }
     modMatrix.process();
 
+    auto oAZ = activeZones;
+    rescanWeakRefs = 0;
     for (int i = 0; i < activeZones; ++i)
     {
         auto z = activeZoneWeakRefs[i];
         assert(z->isActive());
         z->process(e);
+        assert(z->isActive() || rescanWeakRefs > 0);
+        assert(oAZ == activeZones);
+
         /*
          * This is just an optimization to not accumulate. The zone will
          * have already routed to the approprite other bus and output will
@@ -204,6 +209,11 @@ template <bool OS> void Group::processWithOS(scxt::engine::Engine &e)
         }
     }
 
+    if (rescanWeakRefs)
+    {
+        postZoneTraversalRemoveHandler();
+    }
+
     // Groups are always unpitched and stereo
     auto fpitch = 0;
     bool processorConsumesMono[4]{false, false, false, false};
@@ -384,37 +394,33 @@ void Group::addActiveZone(engine::Zone *zwp)
 void Group::removeActiveZone(engine::Zone *zwp)
 {
     assert(activeZones);
+    rescanWeakRefs++;
+}
 
-    // Manage the weak refs
-    // First find the zone
-    int zidx{-1};
-    for (int idx = 0; idx < activeZones; ++idx)
+void Group::postZoneTraversalRemoveHandler()
+{
+    /*
+     * Go backwards down the weak refs removing inactive ones
+     */
+    assert(rescanWeakRefs);
+    assert(activeZones);
+    assert(activeZones >= rescanWeakRefs);
+    for (int i = activeZones - 1; i >= 0; --i)
     {
-        if (activeZoneWeakRefs[idx] == zwp)
+        if (!activeZoneWeakRefs[i]->isActive())
         {
-            zidx = idx;
-            break;
+            rescanWeakRefs--;
+            activeZoneWeakRefs[i] = activeZoneWeakRefs[activeZones - 1];
+            activeZones--;
         }
     }
-    assert(zidx >= 0);
-    // OK so now we want to swap the active zone from the end into my slot
-    activeZoneWeakRefs[zidx] = activeZoneWeakRefs[activeZones - 1];
-
-    activeZones--;
+    assert(rescanWeakRefs == 0);
     if (activeZones == 0)
     {
         ringoutMax = 0;
         ringoutTime = 0;
         updateRingout();
     }
-
-    /*
-    SCLOG("removeZone " << SCD(activeZones));
-    for (int i = 0; i < activeZones; ++i)
-    {
-        SCLOG("removeZone " << activeZoneWeakRefs[i] << " " << activeZoneWeakRefs[i]->getName());
-    }
-     */
 }
 
 engine::Engine *Group::getEngine()
diff --git a/src/engine/group.h b/src/engine/group.h
index 6dcfc7c3..f80ea254 100644
--- a/src/engine/group.h
+++ b/src/engine/group.h
@@ -249,6 +249,8 @@ struct Group : MoveableOnly<Group>,
   private:
     zoneContainer_t zones;
     std::vector<Zone *> activeZoneWeakRefs;
+    uint32_t rescanWeakRefs{0};
+    void postZoneTraversalRemoveHandler();
 };
 } // namespace scxt::engine