From 06fb8f4ea29c179a68d4c46525e5a183441e61da Mon Sep 17 00:00:00 2001
From: Anthony Nicholls <anthony@juce.com>
Date: Tue, 25 Jun 2024 09:36:05 +0100
Subject: [PATCH] ListenerList: Fix a bug where removing a listener during a
 callback in which it had also been added prevents other listeners from being
 called

---
 .../juce_core/containers/juce_ListenerList.h  |  3 +-
 .../containers/juce_ListenerList_test.cpp     | 54 +++++++++++++++----
 2 files changed, 46 insertions(+), 11 deletions(-)

diff --git a/modules/juce_core/containers/juce_ListenerList.h b/modules/juce_core/containers/juce_ListenerList.h
index ee8ec18041..563921951c 100644
--- a/modules/juce_core/containers/juce_ListenerList.h
+++ b/modules/juce_core/containers/juce_ListenerList.h
@@ -135,7 +135,8 @@ public:
         {
             for (auto* it : *iterators)
             {
-                --it->end;
+                if (index < it->end)
+                    --it->end;
 
                 if (index <= it->index)
                     --it->index;
diff --git a/modules/juce_core/containers/juce_ListenerList_test.cpp b/modules/juce_core/containers/juce_ListenerList_test.cpp
index 6466778ee5..8df2d5a81e 100644
--- a/modules/juce_core/containers/juce_ListenerList_test.cpp
+++ b/modules/juce_core/containers/juce_ListenerList_test.cpp
@@ -431,25 +431,59 @@ public:
             ListenerList<Listener> listeners;
             expect (listeners.size() == 0);
 
-            Listener listener;
-            listeners.add (&listener);
-            expect (listeners.size() == 1);
+            Listener listener1;
+            Listener listener2;
+            listeners.add (&listener1);
+            listeners.add (&listener2);
+            expect (listeners.size() == 2);
 
-            bool listenerCalled = false;
+            int numberOfCallbacks = 0;
 
             listeners.call ([&] (auto& l)
             {
                 listeners.remove (&l);
-                expect (listeners.size() == 0);
-
-                listeners.add (&l);
                 expect (listeners.size() == 1);
 
-                listenerCalled = true;
+                listeners.add (&l);
+                expect (listeners.size() == 2);
+
+                ++numberOfCallbacks;
             });
 
-            expect (listenerCalled);
-            expect (listeners.size() == 1);
+            expect (numberOfCallbacks == 2);
+            expect (listeners.size() == 2);
+        }
+
+        beginTest ("Add and remove a nested listener");
+        {
+            struct Listener{};
+
+            ListenerList<Listener> listeners;
+            expect (listeners.size() == 0);
+
+            Listener listener1;
+            Listener listener2;
+            listeners.add (&listener1);
+            listeners.add (&listener2);
+            expect (listeners.size() == 2);
+
+            int numberOfCallbacks = 0;
+
+            listeners.call ([&] (auto)
+            {
+                Listener nestedListener;
+
+                listeners.add (&nestedListener);
+                expect (listeners.size() == 3);
+
+                listeners.remove (&nestedListener);
+                expect (listeners.size() == 2);
+
+                ++numberOfCallbacks;
+            });
+
+            expect (numberOfCallbacks == 2);
+            expect (listeners.size() == 2);
         }
     }