Fixed message discard prevents showing message at all (#1806)

* Check snackbar message duplicate before adding to queue. Removed time check for immediate show of new item.

* Make the task pumping messages long running

* Added null check to item

Added unit tests for IsDuplicate method.

Co-authored-by: Kevin Bost <[email protected]>

Author: greuelpirat

MaterialDesignThemes.Wpf.Tests/SnackbarMessageQueueItemTests.cs

@@ -0,0 +1,60 @@
+using System;
+using Xunit;
+
+namespace MaterialDesignThemes.Wpf.Tests
+{
+    public class SnackbarMessageQueueItemTests
+    {
+        [Fact]
+        public void IsDuplicate_ThrowsOnNullArgument()
+        {
+            SnackbarMessageQueueItem item = CreateItem();
+            Assert.Throws<ArgumentNullException>(() => item.IsDuplicate(null));
+        }
+
+        [Fact]
+        public void IsDuplicate_WithDuplicateItems_ItReturnsTrue()
+        {
+            SnackbarMessageQueueItem item = CreateItem();
+            SnackbarMessageQueueItem other = CreateItem();
+
+            Assert.True(item.IsDuplicate(other));
+        }
+
+        [Fact]
+        public void IsDuplicate_IgnoreDuplicatesIsTrue_ItReturnsFalse()
+        {
+            SnackbarMessageQueueItem item = CreateItem(ignoreDuplicate:true);
+            SnackbarMessageQueueItem other = CreateItem();
+
+            Assert.False(item.IsDuplicate(other));
+        }
+
+        [Fact]
+        public void IsDuplicate_WithDifferentContent_ItReturnsFalse()
+        {
+            SnackbarMessageQueueItem item = CreateItem();
+            SnackbarMessageQueueItem other = CreateItem(content:Guid.NewGuid().ToString());
+
+            Assert.False(item.IsDuplicate(other));
+        }
+
+        [Fact]
+        public void IsDuplicate_WithDifferentActionContent_ItReturnsFalse()
+        {
+            SnackbarMessageQueueItem item = CreateItem();
+            SnackbarMessageQueueItem other = CreateItem(actionContent:Guid.NewGuid().ToString());
+
+            Assert.False(item.IsDuplicate(other));
+        }
+
+
+        private static SnackbarMessageQueueItem CreateItem(
+            string content = "Content",
+            string actionContent = null,
+            bool ignoreDuplicate = false)
+        {
+            return new SnackbarMessageQueueItem(content, TimeSpan.Zero, actionContent:actionContent, ignoreDuplicate: ignoreDuplicate);
+        }
+    }
+}

MaterialDesignThemes.Wpf/SnackbarMessageQueue.cs

@@ -18,7 +18,6 @@ public class SnackbarMessageQueue : ISnackbarMessageQueue, IDisposable
         private readonly ManualResetEvent _disposedEvent = new ManualResetEvent(false);
         private readonly ManualResetEvent _pausedEvent = new ManualResetEvent(false);
         private readonly ManualResetEvent _messageWaitingEvent = new ManualResetEvent(false);
-        private Tuple<SnackbarMessageQueueItem, DateTime> _latestShownItem;
         private int _pauseCounter;
         private bool _isDisposed;
 
@@ -157,7 +156,7 @@ public SnackbarMessageQueue() : this(TimeSpan.FromSeconds(3))
         public SnackbarMessageQueue(TimeSpan messageDuration)
         {
             _messageDuration = messageDuration;
-            Task.Factory.StartNew(PumpAsync);
+            Task.Factory.StartNew(PumpAsync, TaskCreationOptions.LongRunning);
         }
 
         //oh if only I had Disposable.Create in this lib :)  tempted to copy it in like dragabalz, 
@@ -257,27 +256,27 @@ public void Enqueue(object content, object actionContent, Action<object> actionH
 
             var snackbarMessageQueueItem = new SnackbarMessageQueueItem(content, durationOverride ?? _messageDuration,
                 actionContent, actionHandler, actionArgument, promote, neverConsiderToBeDuplicate);
-            if (promote)
-                InsertAsLastNotPromotedNode(snackbarMessageQueueItem);
-            else
-                _snackbarMessages.AddLast(snackbarMessageQueueItem);
+            InsertItem(snackbarMessageQueueItem);
 
             _messageWaitingEvent.Set();
         }
 
-        private void InsertAsLastNotPromotedNode(SnackbarMessageQueueItem snackbarMessageQueueItem)
+        private void InsertItem(SnackbarMessageQueueItem item)
         {
             var node = _snackbarMessages.First;
             while (node != null)
             {
-                if (!node.Value.IsPromoted)
+                if (!IgnoreDuplicate && item.IsDuplicate(node.Value))
+                    return;
+
+                if (item.IsPromoted && !node.Value.IsPromoted)
                 {
-                    _snackbarMessages.AddBefore(node, snackbarMessageQueueItem);
+                    _snackbarMessages.AddBefore(node, item);
                     return;
                 }
                 node = node.Next;
             }
-            _snackbarMessages.AddLast(snackbarMessageQueueItem);
+            _snackbarMessages.AddLast(item);
         }
 
         private async void PumpAsync()
@@ -301,18 +300,9 @@ private async void PumpAsync()
                 //show message
                 if (snackbar != null)
                 {
-                    var message = _snackbarMessages.First.Value;
+                    var message = _snackbarMessages.First!.Value;
+                    await ShowAsync(snackbar, message);
                     _snackbarMessages.RemoveFirst();
-                    if (_latestShownItem == null
-                        || IgnoreDuplicate
-                        || message.IgnoreDuplicate
-                        || !Equals(_latestShownItem.Item1.Content, message.Content)
-                        || !Equals(_latestShownItem.Item1.ActionContent, message.ActionContent)
-                        || _latestShownItem.Item2 <= DateTime.Now.Subtract(_latestShownItem.Item1.Duration))
-                    {
-                        await ShowAsync(snackbar, message);
-                        _latestShownItem = new Tuple<SnackbarMessageQueueItem, DateTime>(message, DateTime.Now);
-                    }
                 }
                 else
                 {

MaterialDesignThemes.Wpf/SnackbarMessageQueueItem.cs

@@ -50,5 +50,22 @@ public SnackbarMessageQueueItem(object content, TimeSpan duration, object action
         /// Still display this message even if it is a duplicate.
         /// </summary>
         public bool IgnoreDuplicate { get; }
+
+        /// <summary>
+        /// Checks if given item is a duplicate to this
+        /// </summary>
+        /// <param name="item">Item to check for duplicate</param>
+        /// <returns><c>true</c> if given item is a duplicate to this, <c>false</c> otherwise</returns>
+        public bool IsDuplicate(SnackbarMessageQueueItem item)
+        {
+            if (item is null)
+            {
+                throw new ArgumentNullException(nameof(item));
+            }
+
+            return !IgnoreDuplicate
+                   && Equals(item.Content, Content)
+                   && Equals(item.ActionContent, ActionContent);
+        }
     }
 }