fix: handle canceled command log updates during shutdown

Catch TaskCanceledException from synchronous log dispatch when the application exits. Use a UI dispatcher timer for log duration updates to avoid background callbacks waiting on a closing dispatcher.

Author: Gadfly

src/ViewModels/CommandLog.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Text;
+using System.Threading.Tasks;
 using Avalonia.Threading;
 using CommunityToolkit.Mvvm.ComponentModel;
 
@@ -58,7 +59,14 @@ public void AppendLine(string line = null)
         {
             if (!Dispatcher.UIThread.CheckAccess())
             {
-                Dispatcher.UIThread.Invoke(() => AppendLine(line));
+                try
+                {
+                    Dispatcher.UIThread.Invoke(() => AppendLine(line));
+                }
+                catch (TaskCanceledException)
+                {
+                    // Pending UI updates are canceled when the application exits.
+                }
             }
             else
             {
@@ -77,7 +85,15 @@ public void Complete()
         {
             if (!Dispatcher.UIThread.CheckAccess())
             {
-                Dispatcher.UIThread.Invoke(Complete);
+                try
+                {
+                    Dispatcher.UIThread.Invoke(Complete);
+                }
+                catch (TaskCanceledException)
+                {
+                    // Pending UI updates are canceled when the application exits.
+                }
+
                 return;
             }
 

src/Views/CommandLogTime.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Threading;
 
 using Avalonia.Controls;
 using Avalonia.Interactivity;
@@ -35,22 +34,22 @@ private void SetupCommandLog(ViewModels.CommandLog log)
             if (log.IsComplete)
                 return;
 
-            _refreshTimer = new Timer(_ =>
+            _refreshTimer = new DispatcherTimer();
+            _refreshTimer.Interval = TimeSpan.FromMilliseconds(100);
+            _refreshTimer.Tick += (_, _) =>
             {
-                Dispatcher.UIThread.Invoke(() =>
-                {
-                    Text = GetDisplayText(log);
-                    if (log.IsComplete)
-                        StopTimer();
-                });
-            }, null, 0, 100);
+                Text = GetDisplayText(log);
+                if (log.IsComplete)
+                    StopTimer();
+            };
+            _refreshTimer.Start();
         }
 
         private void StopTimer()
         {
             if (_refreshTimer is not null)
             {
-                _refreshTimer.Dispose();
+                _refreshTimer.Stop();
                 _refreshTimer = null;
             }
         }
@@ -69,6 +68,6 @@ private static string GetDisplayText(ViewModels.CommandLog log)
             return $"{duration.TotalMilliseconds:G3} ms";
         }
 
-        private Timer _refreshTimer = null;
+        private DispatcherTimer _refreshTimer = null;
     }
 }