Group channels by type and server when filtering in the app

app/Desktop/App.axaml

@@ -55,6 +55,42 @@
             <Setter Property="HorizontalAlignment" Value="Stretch" />
         </Style>
 
+        <Style Selector="TreeViewItem:not(:empty) /template/ Panel#PART_ExpandCollapseChevronContainer">
+            <Setter Property="Cursor" Value="Hand" />
+            <Setter Property="Margin" Value="0 0 5 0" />
+        </Style>
+        <Style Selector="TreeViewItem:empty /template/ Panel#PART_ExpandCollapseChevronContainer">
+            <Setter Property="Margin" Value="10 0" />
+        </Style>
+        <Style Selector="TreeViewItem[Level=0]:empty /template/ Panel#PART_ExpandCollapseChevronContainer">
+            <Setter Property="Margin" Value="0" />
+            <Setter Property="Width" Value="0" />
+        </Style>
+        <Style Selector="TreeViewItem /template/ ToggleButton#PART_ExpandCollapseChevron">
+            <Setter Property="Width" Value="18" />
+            <Setter Property="Height" Value="32" />
+        </Style>
+        <Style Selector="TreeViewItem /template/ ToggleButton#PART_ExpandCollapseChevron > Border">
+            <Setter Property="Padding" Value="2 10 3 10" />
+        </Style>
+
+        <Style Selector="TreeView.noSelection">
+            <Style Selector="^ TreeViewItem /template/ Border#PART_LayoutRoot">
+                <Setter Property="Background" Value="{DynamicResource TreeViewItemBackground}" />
+                <Setter Property="BorderBrush" Value="{DynamicResource TreeViewItemBorderBrush}" />
+            </Style>
+            <Style Selector="^ TreeViewItem /template/ Border#PART_LayoutRoot > ContentPresenter#PART_HeaderPresenter">
+                <Setter Property="Foreground" Value="{DynamicResource TreeViewItemForeground}" />
+            </Style>
+            <Style Selector="^ TreeViewItem:disabled /template/ Border#PART_LayoutRoot">
+                <Setter Property="Background" Value="{DynamicResource TreeViewItemBackgroundDisabled}" />
+                <Setter Property="BorderBrush" Value="{DynamicResource TreeViewItemBorderBrushDisabled}" />
+            </Style>
+            <Style Selector="^ TreeViewItem:disabled /template/ Border#PART_LayoutRoot > ContentPresenter#PART_HeaderPresenter">
+                <Setter Property="Foreground" Value="{DynamicResource TreeViewItemForegroundDisabled}" />
+            </Style>
+        </Style>
+
         <Style Selector="Panel.buttons">
             <Setter Property="Margin" Value="0 20 0 0" />
         </Style>

app/Desktop/Common/AvaloniaReflection.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Collections;
+using System.Reflection;
+using Avalonia.Interactivity;
+
+namespace DHT.Desktop.Common;
+
+static class AvaloniaReflection {
+	private static FieldInfo InteractiveEventHandlersField { get; } = typeof(Interactive).GetField("_eventHandlers", BindingFlags.Instance | BindingFlags.NonPublic)!;
+	
+	public static void Check() {
+		if (InteractiveEventHandlersField == null) {
+			throw new InvalidOperationException("Missing field: " + nameof(InteractiveEventHandlersField));
+		}
+		
+		if (InteractiveEventHandlersField.FieldType.ToString() != "System.Collections.Generic.Dictionary`2[Avalonia.Interactivity.RoutedEvent,System.Collections.Generic.List`1[Avalonia.Interactivity.Interactive+EventSubscription]]") {
+			throw new InvalidOperationException("Invalid field type: " + nameof(InteractiveEventHandlersField) + " = " + InteractiveEventHandlersField.FieldType);
+		}
+	}
+	
+	public static IList? GetEventHandler(Interactive target, RoutedEvent routedEvent) {
+		IDictionary? eventHandlers = (IDictionary?) InteractiveEventHandlersField.GetValue(target);
+		return (IList?) eventHandlers?[routedEvent];
+	}
+}

app/Desktop/Dialogs/CheckBox/CheckBoxDialog.axaml

@@ -8,28 +8,22 @@
         x:DataType="namespace:CheckBoxDialogModel"
         Title="{Binding Title}"
         Icon="avares://DiscordHistoryTracker/Resources/icon.ico"
-        Width="500" SizeToContent="Height" CanResize="False"
+        MinWidth="425" MinHeight="200"
+        Width="500" Height="395" CanResize="True"
         WindowStartupLocation="CenterOwner">
 
     <Window.DataContext>
         <namespace:CheckBoxDialogModel />
     </Window.DataContext>
 
-    <StackPanel Margin="20">
-        <ScrollViewer MaxHeight="400">
-            <ItemsRepeater ItemsSource="{Binding Items}">
-                <ItemsRepeater.ItemTemplate>
-                    <DataTemplate>
-                        <CheckBox IsChecked="{Binding IsChecked}">
-                            <Label>
-                                <TextBlock Text="{Binding Title}" TextWrapping="Wrap" />
-                            </Label>
-                        </CheckBox>
-                    </DataTemplate>
-                </ItemsRepeater.ItemTemplate>
-            </ItemsRepeater>
-        </ScrollViewer>
-        <Panel Classes="buttons">
+    <Window.Styles>
+        <Style Selector="TreeViewItem">
+            <Setter Property="IsExpanded" Value="True" />
+        </Style>
+    </Window.Styles>
+
+    <DockPanel Margin="20 17 20 20">
+        <Panel Classes="buttons" DockPanel.Dock="Bottom">
             <WrapPanel>
                 <Button Command="{Binding SelectAll}" IsEnabled="{Binding !AreAllSelected}">Select All</Button>
                 <Button Command="{Binding SelectNone}" IsEnabled="{Binding !AreNoneSelected}">Select None</Button>
@@ -39,6 +33,19 @@
                 <Button Click="ClickCancel">Cancel</Button>
             </WrapPanel>
         </Panel>
-    </StackPanel>
+        <ScrollViewer DockPanel.Dock="Top">
+            <TreeView Name="TreeView" Classes="noSelection" ItemsSource="{Binding RootItems}" ContainerPrepared="TreeViewOnContainerPrepared">
+                <TreeView.ItemTemplate>
+                    <TreeDataTemplate ItemsSource="{Binding Children}">
+                        <CheckBox IsChecked="{Binding IsChecked}">
+                            <Label>
+                                <TextBlock Text="{Binding Title}" TextWrapping="Wrap" />
+                            </Label>
+                        </CheckBox>
+                    </TreeDataTemplate>
+                </TreeView.ItemTemplate>
+            </TreeView>
+        </ScrollViewer>
+    </DockPanel>
 
 </Window>

app/Desktop/Dialogs/CheckBox/CheckBoxDialog.axaml.cs

@@ -1,6 +1,9 @@
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Avalonia.Input;
 using Avalonia.Interactivity;
+using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.Message;
 
 namespace DHT.Desktop.Dialogs.CheckBox;
@@ -11,6 +14,36 @@ public sealed partial class CheckBoxDialog : Window {
 		InitializeComponent();
 	}
 	
+	private void TreeViewOnContainerPrepared(object? sender, ContainerPreparedEventArgs e) {
+		foreach (object? item in TreeView.Items) {
+			if (item != null && TreeView.ContainerFromItem(item) is TreeViewItem treeViewItem) {
+				treeViewItem.TemplateApplied += TreeViewItemOnTemplateApplied;
+				treeViewItem.GotFocus += TreeViewItemOnGotFocus;
+				treeViewItem.KeyDown += TreeViewItemOnKeyDown;
+			}
+		}
+	}
+	
+	private void TreeViewItemOnTemplateApplied(object? sender, TemplateAppliedEventArgs e) {
+		if (sender is TreeViewItem { HeaderPresenter: Interactive headerPresenter } ) {
+			// Removes support for double-clicking to expand.
+			AvaloniaReflection.GetEventHandler(headerPresenter, DoubleTappedEvent)?.Clear();
+		}
+	}
+	
+	private void TreeViewItemOnGotFocus(object? sender, GotFocusEventArgs e) {
+		if (e.NavigationMethod == NavigationMethod.Tab && sender is TreeViewItem treeViewItem && TreeView.SelectedItem == null) {
+			TreeView.SelectedItem = TreeView.ItemFromContainer(treeViewItem);
+		}
+	}
+	
+	private void TreeViewItemOnKeyDown(object? sender, KeyEventArgs e) {
+		if (e.Key == Key.Space && TreeView.SelectedItem is ICheckBoxItem item) {
+			item.IsChecked = item.IsChecked == false;
+			e.Handled = true;
+		}
+	}
+	
 	public void ClickOk(object? sender, RoutedEventArgs e) {
 		Close(DialogResult.OkCancel.Ok);
 	}

app/Desktop/Dialogs/CheckBox/CheckBoxDialogModel.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Linq;
 using PropertyChanged.SourceGenerator;
@@ -8,64 +9,65 @@ namespace DHT.Desktop.Dialogs.CheckBox;
 partial class CheckBoxDialogModel {
 	public string Title { get; init; } = "";
 	
-	private IReadOnlyList<CheckBoxItem> items = [];
+	private ImmutableArray<ICheckBoxItem> rootItems = [];
 	
-	public IReadOnlyList<CheckBoxItem> Items {
-		get => items;
+	public ImmutableArray<ICheckBoxItem> RootItems {
+		get => rootItems;
 		
 		protected set {
-			foreach (CheckBoxItem item in items) {
+			foreach (ICheckBoxItem item in ICheckBoxItem.GetAllRecursively(rootItems)) {
 				item.PropertyChanged -= OnItemPropertyChanged;
 			}
 			
-			items = value;
+			rootItems = value;
 			
-			foreach (CheckBoxItem item in items) {
+			foreach (ICheckBoxItem item in ICheckBoxItem.GetAllRecursively(rootItems)) {
 				item.PropertyChanged += OnItemPropertyChanged;
 			}
 		}
 	}
 	
-	private bool pauseCheckEvents = false;
+	protected IEnumerable<ICheckBoxItem> AllItems => ICheckBoxItem.GetAllRecursively(RootItems);
 	
-	[DependsOn(nameof(Items))]
-	public bool AreAllSelected => Items.All(static item => item.IsChecked);
+	[DependsOn(nameof(RootItems))]
+	public bool AreAllSelected => RootItems.All(static item => item.IsChecked == true);
 	
-	[DependsOn(nameof(Items))]
-	public bool AreNoneSelected => Items.All(static item => !item.IsChecked);
+	[DependsOn(nameof(RootItems))]
+	public bool AreNoneSelected => RootItems.All(static item => item.IsChecked == false);
+	
+	private bool pauseUpdatingBulkButtons = false;
 	
 	public void SelectAll() => SetAllChecked(true);
 	public void SelectNone() => SetAllChecked(false);
 	
 	private void SetAllChecked(bool isChecked) {
-		pauseCheckEvents = true;
+		pauseUpdatingBulkButtons = true;
 		
-		foreach (CheckBoxItem item in Items) {
+		foreach (ICheckBoxItem item in RootItems) {
 			item.IsChecked = isChecked;
 		}
 		
-		pauseCheckEvents = false;
+		pauseUpdatingBulkButtons = false;
 		UpdateBulkButtons();
 	}
 	
-	private void UpdateBulkButtons() {
-		OnPropertyChanged(new PropertyChangedEventArgs(nameof(Items)));
-	}
-	
 	private void OnItemPropertyChanged(object? sender, PropertyChangedEventArgs e) {
-		if (!pauseCheckEvents && e.PropertyName == nameof(CheckBoxItem.IsChecked)) {
+		if (e.PropertyName == nameof(ICheckBoxItem.IsChecked) && !pauseUpdatingBulkButtons) {
 			UpdateBulkButtons();
 		}
 	}
+	
+	private void UpdateBulkButtons() {
+		OnPropertyChanged(new PropertyChangedEventArgs(nameof(RootItems)));
+	}
 }
 
 sealed class CheckBoxDialogModel<T> : CheckBoxDialogModel {
-	private new IReadOnlyList<CheckBoxItem<T>> Items { get; }
+	public IEnumerable<T> SelectedValues => AllItems.OfType<ICheckBoxItem.Leaf<T>>()
+	                                                .Where(static item => item.IsChecked == true)
+	                                                .Select(static item => item.Value);
 	
-	public IEnumerable<CheckBoxItem<T>> SelectedItems => Items.Where(static item => item.IsChecked);
-	
-	public CheckBoxDialogModel(IEnumerable<CheckBoxItem<T>> items) {
-		this.Items = new List<CheckBoxItem<T>>(items);
-		base.Items = Items;
+	public CheckBoxDialogModel(ImmutableArray<ICheckBoxItem> items) {
+		this.RootItems = items;
 	}
 }

app/Desktop/Dialogs/CheckBox/CheckBoxItem.cs

@@ -1,20 +1,110 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.ComponentModel;
+using System.Linq;
 using PropertyChanged.SourceGenerator;
 
 namespace DHT.Desktop.Dialogs.CheckBox;
 
-partial class CheckBoxItem {
-	public string Title { get; init; } = "";
-	public object? Item { get; init; } = null;
+partial interface ICheckBoxItem : INotifyPropertyChanged {
+	public string Title { get; }
+	public bool? IsChecked { get; set; }
+	
+	public ImmutableArray<ICheckBoxItem> Children { get; }
+	
+	void NotifyIsCheckedChanged();
+	
+	public static IEnumerable<ICheckBoxItem> GetAllRecursively(IEnumerable<ICheckBoxItem> items) {
+		Stack<ICheckBoxItem> stack = new Stack<ICheckBoxItem>(items);
+		
+		while (stack.TryPop(out var item)) {
+			yield return item;
+			
+			foreach (ICheckBoxItem child in item.Children) {
+				stack.Push(child);
+			}
+		}
+	}
+	
+	sealed class NonLeaf : ICheckBoxItem {
+		public string Title { get; }
+		
+		public bool? IsChecked {
+			get {
+				if (Children.Count(static child => child.IsChecked == true) == Children.Length) {
+					return true;
+				}
+				else if (Children.Count(static child => child.IsChecked == false) == Children.Length) {
+					return false;
+				}
+				else {
+					return null;
+				}
+			}
+			
+			set {
+				foreach (ICheckBoxItem child in Children) {
+					if (child is Leaf leaf) {
+						leaf.SetCheckedFromParent(value);
+					}
+					else {
+						child.IsChecked = value;
+					}
+				}
+				
+				NotifyIsCheckedChanged();
+				parent?.NotifyIsCheckedChanged();
+			}
+		}
+		
+		public ImmutableArray<ICheckBoxItem> Children { get; }
+		
+		public event PropertyChangedEventHandler? PropertyChanged;
+		
+		private readonly ICheckBoxItem? parent;
+		
+		public NonLeaf(string title, ICheckBoxItem? parent, Func<ICheckBoxItem, ImmutableArray<ICheckBoxItem>> children) {
+			this.parent = parent;
+			this.Title = title;
+			this.Children = children(this);
+		}
+		
+		public void NotifyIsCheckedChanged() {
+			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(IsChecked)));
+		}
+	}
+	
+	partial class Leaf(string title, ICheckBoxItem? parent, bool isChecked) : ICheckBoxItem {
+		public string Title { get; } = title;
+		
+		public ImmutableArray<ICheckBoxItem> Children => ImmutableArray<ICheckBoxItem>.Empty;
+		
+		public readonly ICheckBoxItem? parent = parent;
 		
 		[Notify]
-	private bool isChecked = false;
+		private bool? isChecked = isChecked;
+		
+		private bool notifyParent = true;
+		
+		public void SetCheckedFromParent(bool? isChecked) {
+			notifyParent = false;
+			IsChecked = isChecked;
+			notifyParent = true;
 		}
 		
-sealed class CheckBoxItem<T> : CheckBoxItem {
-	public new T Item { get; }
+		private void OnIsCheckedChanged() {
+			if (notifyParent) {
+				parent?.NotifyIsCheckedChanged();
+			}
+		}
 		
-	public CheckBoxItem(T item) {
-		this.Item = item;
-		base.Item = item;
+		void ICheckBoxItem.NotifyIsCheckedChanged() {
+			OnPropertyChanged(new PropertyChangedEventArgs(nameof(IsChecked)));
+		}
+	}
+	
+	sealed class Leaf<T>(string title, ICheckBoxItem? parent, T value, bool isChecked) : Leaf(title, parent, isChecked) {
+		public T Value => value;
 	}
 }

app/Desktop/Dialogs/CheckBox/CheckBoxItemList.cs

@@ -0,0 +1,46 @@
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+
+namespace DHT.Desktop.Dialogs.CheckBox;
+
+sealed class CheckBoxItemList<TKey, TValue> where TKey : notnull {
+	private readonly List<INode> rootNodes = [];
+	private readonly Dictionary<TKey, List<INode>> parentNodes = [];
+	
+	public void AddParent(TKey key, string title) {
+		if (!parentNodes.ContainsKey(key)) {
+			List<INode> children = [];
+			rootNodes.Add(new INode.NonLeaf(title, children));
+			parentNodes[key] = children;
+		}
+	}
+	
+	public void Add(TValue value, string title, bool isChecked = false) {
+		rootNodes.Add(new INode.Leaf(title, value, isChecked));
+	}
+	
+	public void Add(TKey key, TValue value, string title, bool isChecked = false) {
+		parentNodes.GetValueOrDefault(key, rootNodes).Add(new INode.Leaf(title, value, isChecked));
+	}
+	
+	public ImmutableArray<ICheckBoxItem> ToCheckBoxItems() {
+		return [..rootNodes.Select(static node => node.ToCheckBoxItem(null))];
+	}
+	
+	private interface INode {
+		ICheckBoxItem ToCheckBoxItem(ICheckBoxItem? parent);
+		
+		sealed record NonLeaf(string Title, List<INode> Children) : INode {
+			public ICheckBoxItem ToCheckBoxItem(ICheckBoxItem? parent) {
+				return new ICheckBoxItem.NonLeaf(Title, parent, self => [..Children.Select(child => child.ToCheckBoxItem(self))]);
+			}
+		}
+		
+		sealed record Leaf(string Title, TValue Value, bool IsChecked) : INode {
+			public ICheckBoxItem ToCheckBoxItem(ICheckBoxItem? parent) {
+				return new ICheckBoxItem.Leaf<TValue>(Title, parent, Value, IsChecked);
+			}
+		}
+	}
+}

app/Desktop/Main/Controls/MessageFilterPanelModel.cs

@@ -1,9 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reactive.Linq;
-using System.Text;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.ReactiveUI;
@@ -185,51 +186,64 @@ sealed partial class MessageFilterPanelModel : IDisposable {
 		FilterStatisticsText = verb + " " + exportedMessageCountStr + " out of " + totalMessageCountStr + " message" + (totalMessageCount is null or 1 ? "." : "s.");
 	}
 	
+	[SuppressMessage("ReSharper", "NotAccessedPositionalProperty.Local")]
+	[SuppressMessage("ReSharper", "MemberCanBePrivate.Local")]
+	private readonly record struct ChannelFilterKey(byte Type, ulong? ServerId, string Title) : IComparable<ChannelFilterKey> {
+		public static ChannelFilterKey DirectMessages { get; } = new (Type: 1, ServerId: null, Title: "Direct Messages");
+		public static ChannelFilterKey GroupMessages { get; } = new (Type: 2, ServerId: null, Title: "Group Messages");
+		public static ChannelFilterKey Unknown { get; } = new (Type: 4, ServerId: null, Title: "Unknown");
+		
+		public static ChannelFilterKey For(DHT.Server.Data.Server server) {
+			return server.Type switch {
+				ServerType.Server        => new ChannelFilterKey(Type: 3, server.Id, "Server - " + server.Name),
+				ServerType.Group         => GroupMessages,
+				ServerType.DirectMessage => DirectMessages,
+				_                        => Unknown,
+			};
+		}
+		
+		public bool Equals(ChannelFilterKey other) {
+			return Type == other.Type && ServerId == other.ServerId;
+		}
+		
+		public override int GetHashCode() {
+			return HashCode.Combine(Type, ServerId);
+		}
+		
+		public int CompareTo(ChannelFilterKey other) {
+			int result = Type.CompareTo(other.Type);
+			if (result != 0) {
+				return result;
+			}
+			else {
+				return Title.CompareTo(other.Title);
+			}
+		}
+	}
+	
 	public async Task OpenChannelFilterDialog() {
-		async Task<List<CheckBoxItem<ulong>>> PrepareChannelItems(ProgressDialog dialog) {
-			var items = new List<CheckBoxItem<ulong>>();
+		async Task<ImmutableArray<ICheckBoxItem>> PrepareChannelItems(ProgressDialog dialog) {
+			CheckBoxItemList<ChannelFilterKey, ulong> items = new CheckBoxItemList<ChannelFilterKey, ulong>();
 			Dictionary<ulong, DHT.Server.Data.Server> servers = await state.Db.Servers.Get().ToDictionaryAsync(static server => server.Id);
 			
-			await foreach (Channel channel in state.Db.Channels.Get()) {
-				ulong channelId = channel.Id;
-				string channelName = channel.Name;
-				
-				string title;
-				if (servers.TryGetValue(channel.Server, out var server)) {
-					var titleBuilder = new StringBuilder();
-					ServerType? serverType = server.Type;
-					
-					titleBuilder.Append('[')
-					            .Append(ServerTypes.ToString(serverType))
-					            .Append("] ");
-					
-					if (serverType == ServerType.DirectMessage) {
-						titleBuilder.Append(channelName);
-					}
-					else {
-						titleBuilder.Append(server.Name)
-						            .Append(" - ")
-						            .Append(channelName);
+			foreach (ChannelFilterKey channelFilterKey in servers.Values.Select(ChannelFilterKey.For).Order()) {
+				items.AddParent(channelFilterKey, channelFilterKey.Title);
 			}
 			
-					title = titleBuilder.ToString();
-				}
-				else {
-					title = channelName;
+			await foreach (Channel channel in state.Db.Channels.Get().OrderBy(static channel => channel.Position ?? int.MinValue).ThenBy(static channel => channel.Name)) {
+				ChannelFilterKey key = servers.TryGetValue(channel.Server, out var server)
+					                       ? ChannelFilterKey.For(server)
+					                       : ChannelFilterKey.Unknown;
+				
+				items.Add(key, channel.Id, channel.Name, isChecked: IncludedChannels == null || IncludedChannels.Contains(channel.Id));
 			}
 			
-				items.Add(new CheckBoxItem<ulong>(channelId) {
-					Title = title,
-					IsChecked = IncludedChannels == null || IncludedChannels.Contains(channelId),
-				});
-			}
-			
-			return items;
+			return items.ToCheckBoxItems();
 		}
 		
 		const string Title = "Included Channels";
 		
-		List<CheckBoxItem<ulong>> items;
+		ImmutableArray<ICheckBoxItem> items;
 		try {
 			items = await ProgressDialog.ShowIndeterminate(window, Title, "Loading channels...", PrepareChannelItems);
 		} catch (Exception e) {
@@ -244,22 +258,27 @@ sealed partial class MessageFilterPanelModel : IDisposable {
 	}
 	
 	public async Task OpenUserFilterDialog() {
-		async Task<List<CheckBoxItem<ulong>>> PrepareUserItems(ProgressDialog dialog) {
-			var checkBoxItems = new List<CheckBoxItem<ulong>>();
+		async Task<ImmutableArray<ICheckBoxItem>> PrepareUserItems(ProgressDialog dialog) {
+			CheckBoxItemList<ulong, ulong> items = new CheckBoxItemList<ulong, ulong>();
 			
-			await foreach (User user in state.Db.Users.Get()) {
-				checkBoxItems.Add(new CheckBoxItem<ulong>(user.Id) {
-					Title = user.DisplayName == null ? user.Name : $"{user.DisplayName} ({user.Name})",
-					IsChecked = IncludedUsers == null || IncludedUsers.Contains(user.Id),
-				});
+			static string GetDisplayName(User user) {
+				return user.DisplayName == null ? user.Name : $"{user.DisplayName} ({user.Name})";
 			}
 			
-			return checkBoxItems;
+			await foreach ((ulong id, string name) in state.Db.Users.Get().Select(static user => (user.Id, GetDisplayName(user))).OrderBy(static pair => pair.Item2)) {
+				items.Add(
+					value: id,
+					title: name,
+					isChecked: IncludedUsers == null || IncludedUsers.Contains(id)
+				);
+			}
+			
+			return items.ToCheckBoxItems();
 		}
 		
 		const string Title = "Included Users";
 		
-		List<CheckBoxItem<ulong>> items;
+		ImmutableArray<ICheckBoxItem> items;
 		try {
 			items = await ProgressDialog.ShowIndeterminate(window, Title, "Loading users...", PrepareUserItems);
 		} catch (Exception e) {
@@ -273,9 +292,7 @@ sealed partial class MessageFilterPanelModel : IDisposable {
 		}
 	}
 	
-	private async Task<HashSet<ulong>?> OpenIdFilterDialog(string title, List<CheckBoxItem<ulong>> items) {
-		items.Sort(static (item1, item2) => item1.Title.CompareTo(item2.Title));
-		
+	private async Task<HashSet<ulong>?> OpenIdFilterDialog(string title, ImmutableArray<ICheckBoxItem> items) {
 		var model = new CheckBoxDialogModel<ulong>(items) {
 			Title = title,
 		};
@@ -283,7 +300,7 @@ sealed partial class MessageFilterPanelModel : IDisposable {
 		var dialog = new CheckBoxDialog { DataContext = model };
 		var result = await dialog.ShowDialog<DialogResult.OkCancel>(window);
 		
-		return result == DialogResult.OkCancel.Ok ? model.SelectedItems.Select(static item => item.Item).ToHashSet() : null;
+		return result == DialogResult.OkCancel.Ok ? model.SelectedValues.ToHashSet() : null;
 	}
 	
 	public MessageFilter CreateFilter() {

app/Desktop/Program.cs

@@ -2,6 +2,7 @@
 using System.Globalization;
 using System.Reflection;
 using Avalonia;
+using DHT.Desktop.Common;
 using DHT.Utils.Logging;
 using DHT.Utils.Resources;
 
@@ -57,6 +58,8 @@ static class Program {
 	}
 	
 	private static AppBuilder BuildAvaloniaApp() {
+		AvaloniaReflection.Check();
+		
 		return AppBuilder.Configure<App>()
 		                 .UsePlatformDetect()
 		                 .WithInterFont()