Add chapters display, gray out fixed tracks, spacebar preview

MainWindow.xaml

@@ -233,6 +233,12 @@
                                         <Trigger Property="IsSelected" Value="True">
                                             <Setter Property="Background" Value="{DynamicResource AccentFillColorSecondaryBrush}"/>
                                         </Trigger>
+                                        <DataTrigger Binding="{Binding Type}" Value="video">
+                                            <Setter Property="Opacity" Value="0.5"/>
+                                        </DataTrigger>
+                                        <DataTrigger Binding="{Binding Type}" Value="chapters">
+                                            <Setter Property="Opacity" Value="0.5"/>
+                                        </DataTrigger>
                                     </Style.Triggers>
                                 </Style>
                             </DataGrid.RowStyle>
@@ -259,13 +265,14 @@
                                     <DataGridTemplateColumn.CellTemplate>
                                         <DataTemplate>
                                             <CheckBox IsChecked="{Binding Copy, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
+                                                      IsEnabled="{Binding IsEditable}"
                                                       HorizontalAlignment="Center" VerticalAlignment="Center"/>
                                         </DataTemplate>
                                     </DataGridTemplateColumn.CellTemplate>
                                 </DataGridTemplateColumn>
 
                                 <DataGridTextColumn Header="ID"
-                                                    Binding="{Binding Id}" Width="45" IsReadOnly="True"/>
+                                                    Binding="{Binding IdDisplay}" Width="45" IsReadOnly="True"/>
                                 <DataGridTextColumn Header="Codec"
                                                     Binding="{Binding Codec}" Width="185" IsReadOnly="True"/>
                                 <DataGridTextColumn Header="Language"

MainWindow.xaml.cs

@@ -1,5 +1,6 @@
 using System.Collections.ObjectModel;
 using System.ComponentModel;
+using System.Diagnostics;
 using System.IO;
 using System.Threading;
 using System.Windows;
@@ -357,6 +358,13 @@ public partial class MainWindow : FluentWindow
     /// </summary>
     private void FileQueueList_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)
     {
+        if (e.Key == System.Windows.Input.Key.Space)
+        {
+            OpenSelectedFileInDefaultPlayer();
+            e.Handled = true;
+            return;
+        }
+
         if (e.Key != System.Windows.Input.Key.Delete) return;
 
         var selected = FileQueueList.SelectedItems.Cast<QueuedFileItem>().ToList();
@@ -371,6 +379,25 @@ public partial class MainWindow : FluentWindow
         e.Handled = true;
     }
 
+    /// <summary>
+    /// Opens the currently-selected queue item with whatever application
+    /// Windows has associated with .mkv files (typically the default video
+    /// player), so the user can quickly preview a file without leaving the app.
+    /// </summary>
+    private void OpenSelectedFileInDefaultPlayer()
+    {
+        if (FileQueueList.SelectedItem is not QueuedFileItem item) return;
+
+        try
+        {
+            Process.Start(new ProcessStartInfo(item.FilePath) { UseShellExecute = true });
+        }
+        catch (Exception ex)
+        {
+            StatusText.Text = $"Couldn't open {item.FileName}: {ex.Message}";
+        }
+    }
+
     private void ClearQueueButton_Click(object sender, RoutedEventArgs e)
     {
         foreach (var item in _fileQueue)

Models/MkvModels.cs

@@ -13,6 +13,15 @@ public class MkvIdentifyResult
 
     [JsonPropertyName("tracks")]
     public List<MkvTrack> Tracks { get; set; } = new();
+
+    [JsonPropertyName("chapters")]
+    public List<MkvChapters> Chapters { get; set; } = new();
+}
+
+public class MkvChapters
+{
+    [JsonPropertyName("num_entries")]
+    public int NumEntries { get; set; }
 }
 
 public class MkvTrack

Models/TrackItem.cs

@@ -44,6 +44,20 @@ public class TrackItem : INotifyPropertyChanged
     /// </summary>
     public string DisplayName => Type == "subtitles" ? $"{Codec}/{Name}" : Name;
 
+    /// <summary>
+    /// Video is always kept, and chapters (a synthetic pseudo-track, not a
+    /// real mkvmerge track) are always kept too — neither is user-selectable,
+    /// so their Copy checkbox is shown checked but disabled.
+    /// </summary>
+    public bool IsEditable => Type is "audio" or "subtitles";
+
+    /// <summary>
+    /// Chapters aren't a real track and have no track ID; show a dash
+    /// instead of a meaningless number.
+    /// </summary>
+    public string IdDisplay => Type == "chapters" ? "—" : Id.ToString();
+
+
     public bool Copy
     {
         get => _copy;

Services/MkvService.cs

@@ -110,7 +110,7 @@ public class MkvService
         MkvTrack? preferredAudio = eligibleAudio.FirstOrDefault(t => t.Properties?.AudioChannels == 2)
                                     ?? eligibleAudio.FirstOrDefault();
 
-        return info.Tracks.Select(t =>
+        var items = info.Tracks.Select(t =>
         {
             bool copy = t.Type switch
             {
@@ -136,6 +136,22 @@ public class MkvService
                 Copy = copy,
             };
         }).ToList();
+
+        int chapterCount = info.Chapters.Sum(c => c.NumEntries);
+        if (chapterCount > 0)
+        {
+            items.Add(new TrackItem
+            {
+                Id = -1,
+                Type = "chapters",
+                Codec = string.Empty,
+                Language = string.Empty,
+                Name = $"Chapters ({chapterCount})",
+                Copy = true,
+            });
+        }
+
+        return items;
     }
 
     /// <summary>