From 93291cb42e372e24a4202369c2f9f653a19d9f59 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jindra=20Pet=C5=99=C3=ADk?= <jindra.petrik@gmail.com>
Date: Tue, 13 May 2025 19:47:39 +0200
Subject: [PATCH] Fixed: #2455 Commandline export
 ConcurrentModificationException

---
 CHANGELOG.md                                  |  2 ++
 .../com/jpexs/helpers/CancellableWorker.java  | 26 ++++++++++++-------
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6fc816408..5006c286c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -75,6 +75,7 @@ All notable changes to this project will be documented in this file.
 - FLA export - Rounding errors on COLORMATRIXFILTER contrast
 - Filters - image bounds
 - Simple editor - Exceptions caused by not setting timelined when modifying PlaceObject
+- [#2455] Commandline export ConcurrentModificationException
 
 ### Removed
 - Option to preview flash items via ActiveX component is no longer available.
@@ -3795,6 +3796,7 @@ Major version of SWF to XML export changed to 2.
 [#2355]: https://www.free-decompiler.com/flash/issues/2355
 [#2419]: https://www.free-decompiler.com/flash/issues/2419
 [#2454]: https://www.free-decompiler.com/flash/issues/2454
+[#2455]: https://www.free-decompiler.com/flash/issues/2455
 [#2375]: https://www.free-decompiler.com/flash/issues/2375
 [#2374]: https://www.free-decompiler.com/flash/issues/2374
 [#2389]: https://www.free-decompiler.com/flash/issues/2389
diff --git a/libsrc/ffdec_lib/src/com/jpexs/helpers/CancellableWorker.java b/libsrc/ffdec_lib/src/com/jpexs/helpers/CancellableWorker.java
index ad7c4a6c5..3dcdf0d6e 100644
--- a/libsrc/ffdec_lib/src/com/jpexs/helpers/CancellableWorker.java
+++ b/libsrc/ffdec_lib/src/com/jpexs/helpers/CancellableWorker.java
@@ -155,7 +155,9 @@ public abstract class CancellableWorker<T> implements RunnableFuture<T> {
 
     @Override
     public final void run() {
-        workers.add(this);
+        synchronized (CancellableWorker.class) {
+            workers.add(this);
+        }        
         future.run();
     }
 
@@ -245,7 +247,9 @@ public abstract class CancellableWorker<T> implements RunnableFuture<T> {
         if (thread != null && thread2Worker.get(thread) == this) {
             //thread2Worker.remove(thread);
         }
-        workers.remove(this);
+        synchronized (CancellableWorker.class) {
+            workers.remove(this);
+        }
         done();
     }
 
@@ -282,15 +286,17 @@ public abstract class CancellableWorker<T> implements RunnableFuture<T> {
      * Cancels all background threads.
      */
     public static void cancelBackgroundThreads() {
-        List<CancellableWorker> oldWorkers = workers;
-        workers = Collections.synchronizedList(new ArrayList<CancellableWorker>());
-        for (CancellableWorker worker : oldWorkers) {
-            if (worker != null) {
-                worker.cancel(true);
-            } else {
-                Logger.getLogger(CancellableWorker.class.getName()).log(Level.SEVERE, "worker is null");
+        synchronized (CancellableWorker.class) {
+            List<CancellableWorker> oldWorkers = workers;
+            workers = Collections.synchronizedList(new ArrayList<CancellableWorker>());
+            for (CancellableWorker worker : oldWorkers) {
+                if (worker != null) {
+                    worker.cancel(true);
+                } else {
+                    Logger.getLogger(CancellableWorker.class.getName()).log(Level.SEVERE, "worker is null");
+                }
             }
-        }
+        }        
     }
 
     public static void cancelThread(Thread t) {