fix objectlist add task synchronization;

Author: Carl Chang

Helpers/LoadHelper.cs

@@ -631,7 +631,6 @@ public static IEnumerable<ObjectInfo> GetAll(string path) {
 
         public static void CacheFolder(string path, ref CancellationTokenSource tknSrc, object tknLock, Action<string, int, int> callback) {
             tknSrc?.Cancel();
-            tknSrc?.Dispose();
             Monitor.Enter(tknLock);
             tknSrc = new CancellationTokenSource();
             var count = 0;

Helpers/ObservableClasses.cs

@@ -24,6 +24,7 @@ public class ObservableKeyedCollection<TKey, TItem> : KeyedCollection<TKey, TIte
         /// Needs either a delegate or a property name to get the key from the child item.
         /// Using a delegate should be faster than the property name which will use reflection.
         /// If TItem implements both INotifyCollectionChanged and INotifyCollectionChanging, the name of the key property is also needed for key updating to work.
+		/// <para>Be aware that this is not thread-safe.</para>
         /// </summary>
         public ObservableKeyedCollection(Func<TItem, TKey> getKeyFunc = null, string keyPropName = null, IEnumerable<TItem> collection = null) {
             if (getKeyFunc == null && keyPropName == null)

MainWindow.xaml.cs

@@ -45,7 +45,7 @@ public string CurrentPath {
             virWrapPanel.Children.Cast<ContentPresenter>().Count(cp => ((ObjectInfo)cp.Content).SourcePaths?.Length > 0) * 200 + App.Random.Next(2, 7) * 1000));
 
         internal CancellationTokenSource tknSrc_LoadThumb;
-        internal readonly object lock_LoadThumb = new object();
+        private readonly object lock_LoadThumb = new object();
 
         private VirtualizingWrapPanel virWrapPanel;
         private Rect lastWindowRect;
@@ -96,7 +96,6 @@ private async void MainWin_Closing(object sender, CancelEventArgs e) {
             Setting.ThumbnailSize.PropertyChanged -= ThumbnailSizeChanged;
 
             tknSrc_LoadThumb?.Cancel();
-            tknSrc_LoadThumb?.Dispose();
             while (tknSrc_LoadThumb != null) { await Task.Delay(100); }
 
             Dispatcher.Invoke(() => ObjectList.Clear());
@@ -156,10 +155,13 @@ private void openFolderPrompt() {
             OpenFolderDialog(this, path => Task.Run(() => LoadPath(path)));
         }
 
-        private async void callback_AddToImageList(ObjectInfo objInfo) {
+        /// <summary>
+        /// This needs to be synchronous for the cancallation to work.
+        /// </summary>
+        private void callback_AddToImageList(ObjectInfo objInfo) {
             //exclude non-image items in immersion mode
             if (Setting.ImmersionMode && objInfo.SourcePaths == null) {
-                objInfo.SourcePaths = await GetSourcePathsAsync(objInfo);//update needed to exclude items that do not have thumbs
+                objInfo.SourcePaths = GetSourcePaths(objInfo);//update needed to exclude items that do not have thumbs
                 if (objInfo.SourcePaths == null || objInfo.SourcePaths.Length == 0)
                     return;
             }
@@ -220,7 +222,6 @@ internal void LoadPath(ObjectInfo objInfo, ViewWindow viewWin = null) {
                 //directory -> load thumbs
                 try {
                     tknSrc_LoadThumb?.Cancel();
-                    tknSrc_LoadThumb?.Dispose();
                     Monitor.Enter(lock_LoadThumb);
                     tknSrc_LoadThumb = new CancellationTokenSource();
                     preRefreshActions();
@@ -253,7 +254,6 @@ internal void LoadPath(ObjectInfo objInfo, ViewWindow viewWin = null) {
                 //archive itself -> extract and load thumbs
                 try {
                     tknSrc_LoadThumb?.Cancel();
-                    tknSrc_LoadThumb?.Dispose();
                     Monitor.Enter(lock_LoadThumb);
                     tknSrc_LoadThumb = new CancellationTokenSource();
                     preRefreshActions();
@@ -265,7 +265,6 @@ internal void LoadPath(ObjectInfo objInfo, ViewWindow viewWin = null) {
                         CldInfoCallback = callback_AddToImageList,
                     }, tknSrc_LoadThumb);
                     Dispatcher.Invoke(() => scrollPosition());
-                    //postRefreshActions();
                 }
                 finally {
                     tknSrc_LoadThumb.Dispose();