Improve message history loading.

Author: matthew4850

src/Quarrel.ViewModels/Extensions/System.Collections.ObjectModel/ObservableRangeCollection.cs

@@ -78,7 +78,10 @@ public void InsertRange(int index, IEnumerable<T> collection, NotifyCollectionCh
             OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
             if (changedItems.Count > 0)
             {
-                OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, changedItems, index));
+                for (int i = changedItems.Count-1; i >= 0; i--)
+                {
+                    OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, new List<T>{ changedItems[i] }, index));
+                }
             }
         }
 

src/Quarrel.ViewModels/ViewModels/Panels/MessagesViewModel.cs

@@ -81,25 +81,28 @@ public bool IsLoading
         public async void LoadOlderMessages()
         {
             if (Source.Count == 0) return;
-
+            if (IsLoading) return;
             await _semaphore.WaitAsync();
+            IsLoading = true;
             try
             {
                 ulong beforeId = Source[0].Message.Id;
                 IBindableMessageChannel? channel = SelectedChannel as IBindableMessageChannel;
                 Guard.IsNotNull(channel, nameof(channel));
 
                 // Load messages
-                IsLoading = true;
                 var messages = await _discordService.GetChannelMessagesAsync(channel, beforeId);
-                var bindableMessages = ParseMessages(messages);
+                if (messages.Length > 0)
+                {
+                    var bindableMessages = ParseMessages(messages);
 
-                // Add messages to the UI and mark loading as finished
-                Source.InsertRange(0, bindableMessages);
-                IsLoading = false;
+                    // Add messages to the UI and mark loading as finished
+                    Source.InsertRange(0, bindableMessages);
+                }
             }
             finally
             {
+                IsLoading = false;
                 _semaphore.Release();
             }
         }

src/Quarrel/DataTemplates/MessageTemplates.xaml

@@ -74,7 +74,7 @@
                     </StackPanel>
 
                     <StackPanel Grid.Row="1">
-                        <markdown:MessageRenderer Text="{x:Bind Message.Content, Mode=OneWay}" Context="{x:Bind}"
+                        <markdown:MessageRenderer Text="{x:Bind Content, Mode=OneWay}" Context="{x:Bind Mode=OneWay}"
                                                   HorizontalAlignment="Left"/>
 
                         <ItemsControl ItemsSource="{x:Bind Message.Attachments}"