Empty Document Host Content + Template Support

docfx/articles/dock-controls-reference.md

@@ -63,9 +63,11 @@ Unless noted otherwise, the properties listed are Avalonia styled properties and
 | `HeaderTemplate` | `IDataTemplate` | Tab header template. |
 | `ModifiedTemplate` | `IDataTemplate` | Modified indicator template. |
 | `CloseTemplate` | `IDataTemplate` | Close button template. |
+| `EmptyContentTemplate` | `IDataTemplate?` | Template used to render model `EmptyContent` when no tabbed documents are visible. |
 | `CloseButtonTheme` | `ControlTheme?` | Theme for the close button. |
 | `IsActive` | `bool` | Active document state (drives `:active`). |
 | `TabsLayout` | `DocumentTabLayout` | Tab placement for the document dock. |
+| `HasVisibleDockables` | `bool` | `true` when one or more tabbed dockables are visible (read-only). |
 
 ### ToolControl
 
@@ -156,9 +158,11 @@ Unless noted otherwise, the properties listed are Avalonia styled properties and
 | `HeaderTemplate` | `IDataTemplate` | Window header template. |
 | `ModifiedTemplate` | `IDataTemplate` | Modified indicator template. |
 | `CloseTemplate` | `IDataTemplate` | Close button template. |
+| `EmptyContentTemplate` | `IDataTemplate?` | Template used to render the model `EmptyContent` placeholder when no MDI documents are visible. |
 | `CloseButtonTheme` | `ControlTheme?` | Theme for the close button. |
 | `LayoutManager` | `IMdiLayoutManager?` | Layout manager forwarded to the MDI panel. |
 | `IsActive` | `bool` | Active state (drives `:active`). |
+| `HasVisibleDocuments` | `bool` | `true` when one or more MDI documents are visible (read-only). |
 
 ### MdiDocumentWindow
 

docfx/articles/dock-mdi.md

@@ -50,6 +50,26 @@ The Avalonia controls expose additional properties for theming:
 - `MdiDocumentControl` forwards `IconTemplate`, `HeaderTemplate`, `ModifiedTemplate`, `CloseTemplate`, and `CloseButtonTheme` to each window.
 - `MdiDocumentWindow` exposes `DocumentContextMenu`, `MdiState`, and `IsActive` for styling or interaction.
 
+`IDocumentDock.EmptyContent` defines placeholder content shown when a document host has no visible dockables. In MDI mode, `MdiDocumentControl.EmptyContentTemplate` can optionally control how that content is rendered:
+
+```csharp
+using Avalonia.Controls;
+using Avalonia.Controls.Templates;
+
+var documents = new DocumentDock
+{
+    LayoutMode = DocumentLayoutMode.Mdi,
+    EmptyContent = "No documents are open"
+};
+
+var mdiDocumentControl = new MdiDocumentControl
+{
+    DataContext = documents,
+    EmptyContentTemplate = new FuncDataTemplate<string>((text, _) =>
+        new TextBlock { Text = text }, true)
+};
+```
+
 To customize the layout algorithm, provide an `IMdiLayoutManager` implementation. It can be assigned on `MdiDocumentControl.LayoutManager` (which the default template forwards to `MdiLayoutPanel`):
 
 ```csharp

docfx/articles/dock-model-controls.md

@@ -70,6 +70,10 @@ are placed.
 `IDocumentDock.LayoutMode` switches between tabbed documents and classic MDI
 windows. When MDI mode is enabled the dock exposes commands for cascade and
 tile operations, and documents implement `IMdiDocument` to store window state.
+`IDocumentDock.EmptyContent` can provide placeholder content when either
+document host is empty (tabbed or MDI). Template rendering for that content is
+configured in the Avalonia layer via `DocumentControl.EmptyContentTemplate`
+and `MdiDocumentControl.EmptyContentTemplate`.
 
 `IDocumentDockFactory` exposes a `DocumentFactory` delegate that is used by
 the `CreateDocument` command. When assigned, this factory is invoked to

docfx/articles/dock-reference.md

@@ -52,6 +52,7 @@ from a saved state.
 - `TabsLayout` chooses where the tabs appear using the `DocumentTabLayout` enum
 - `LayoutMode` switches between `Tabbed` and `Mdi` layouts
 - `CloseButtonShowMode` controls when document close buttons appear
+- `EmptyContent` defines placeholder content shown when a tabbed or MDI document host has no visible dockables
 - `CanCreateDocument` and `CreateDocument` control the new-document command
 - `CascadeDocuments`, `TileDocumentsHorizontal`, `TileDocumentsVertical`, and `RestoreDocuments` are MDI helpers
 
@@ -124,9 +125,9 @@ These properties allow you to customize the context menus, flyouts, and button t
 
 Dock exposes template properties for tab headers and MDI windows:
 
-- `DocumentControl`: `IconTemplate`, `HeaderTemplate`, `ModifiedTemplate`, `CloseTemplate`, `CloseButtonTheme`, `IsActive`, `TabsLayout`.
+- `DocumentControl`: `IconTemplate`, `HeaderTemplate`, `ModifiedTemplate`, `CloseTemplate`, `EmptyContentTemplate`, `CloseButtonTheme`, `IsActive`, `TabsLayout`, `HasVisibleDockables`.
 - `ToolControl`: `IconTemplate`, `HeaderTemplate`, `ModifiedTemplate`.
-- `MdiDocumentControl`: `IconTemplate`, `HeaderTemplate`, `ModifiedTemplate`, `CloseTemplate`, `CloseButtonTheme`, `LayoutManager`, `IsActive`.
+- `MdiDocumentControl`: `IconTemplate`, `HeaderTemplate`, `ModifiedTemplate`, `CloseTemplate`, `EmptyContentTemplate`, `CloseButtonTheme`, `LayoutManager`, `IsActive`, `HasVisibleDocuments`.
 - `MdiDocumentWindow`: `IconTemplate`, `HeaderTemplate`, `ModifiedTemplate`, `CloseTemplate`, `CloseButtonTheme`, `DocumentContextMenu`, `IsActive`, `MdiState`.
 
 Use these to customize headers, icons, and modified indicators in styles or templates. See [Styling and theming](dock-styling.md) and [MDI document layout](dock-mdi.md) for details.

src/Dock.Avalonia.Themes.Fluent/Controls/DocumentControl.axaml

@@ -118,17 +118,27 @@
           <Grid x:Name="PART_Grid"
                 IsVisible="{Binding #PART_TabStrip.IsVisible}" />
           <Border x:Name="PART_Border">
-            <DockableControl DataContext="{Binding ActiveDockable}"
-                             TrackingMode="Visible">
-              <ContentControl x:Name="PART_ContentPresenter"
-                              Content="{Binding}"
-                              HorizontalAlignment="Stretch"
-                              VerticalAlignment="Stretch">
-                <ContentControl.ContentTemplate>
-                  <ControlRecyclingDataTemplate Parent="{Binding #PART_ContentPresenter}" />
-                </ContentControl.ContentTemplate>
-              </ContentControl>
-            </DockableControl>
+            <Grid>
+              <DockableControl DataContext="{Binding ActiveDockable}"
+                               TrackingMode="Visible"
+                               IsVisible="{Binding $parent[DocumentControl].HasVisibleDockables}">
+                <ContentControl x:Name="PART_ContentPresenter"
+                                Content="{Binding}"
+                                HorizontalAlignment="Stretch"
+                                VerticalAlignment="Stretch">
+                  <ContentControl.ContentTemplate>
+                    <ControlRecyclingDataTemplate Parent="{Binding #PART_ContentPresenter}" />
+                  </ContentControl.ContentTemplate>
+                </ContentControl>
+              </DockableControl>
+
+              <ContentControl x:Name="PART_EmptyContentHost"
+                              Content="{Binding EmptyContent}"
+                              ContentTemplate="{Binding $parent[DocumentControl].EmptyContentTemplate}"
+                              HorizontalContentAlignment="Center"
+                              VerticalContentAlignment="Center"
+                              IsVisible="{Binding !$parent[DocumentControl].HasVisibleDockables}" />
+            </Grid>
           </Border>
         </DockPanel>
       </ControlTemplate>

src/Dock.Avalonia.Themes.Fluent/Controls/MdiDocumentControl.axaml

@@ -68,38 +68,48 @@
                 DockProperties.IsDropArea="True"
                 DockProperties.IsDockTarget="True"
                 DockProperties.DockAdornerHost="{Binding RelativeSource={RelativeSource Self}}">
-          <ItemsControl x:Name="PART_ItemsControl"
-                        Classes="MdiLayoutItems"
-                        ItemsSource="{Binding VisibleDockables}">
-            <ItemsControl.Styles>
-              <Style Selector="ItemsControl.MdiLayoutItems > ContentPresenter"
-                     x:DataType="dmc:IMdiDocument">
-                <Setter Property="ZIndex" Value="{Binding MdiZIndex}" />
-              </Style>
-            </ItemsControl.Styles>
-            <ItemsControl.ItemsPanel>
-              <ItemsPanelTemplate>
-                <controls:MdiLayoutPanel LayoutManager="{Binding $parent[controls:MdiDocumentControl].LayoutManager}" />
-              </ItemsPanelTemplate>
-            </ItemsControl.ItemsPanel>
-            <ItemsControl.ItemTemplate>
-              <DataTemplate DataType="dmc:IMdiDocument">
-                <controls:MdiDocumentWindow IconTemplate="{Binding $parent[controls:MdiDocumentControl].IconTemplate}"
-                                            HeaderTemplate="{Binding $parent[controls:MdiDocumentControl].HeaderTemplate}"
-                                            ModifiedTemplate="{Binding $parent[controls:MdiDocumentControl].ModifiedTemplate}"
-                                            CloseTemplate="{Binding $parent[controls:MdiDocumentControl].CloseTemplate}"
-                                            CloseButtonTheme="{Binding $parent[controls:MdiDocumentControl].CloseButtonTheme}"
-                                            DocumentContextMenu="{DynamicResource MdiDocumentWindowContextMenu}"
-                                            MdiState="{Binding MdiState}"
-                                            ZIndex="{Binding MdiZIndex}"
-                                            DockProperties.IsDropArea="True"
-                                            DockProperties.IsDockTarget="True"
-                                            DockProperties.ShowDockIndicatorOnly="True"
-                                            DockProperties.IndicatorDockOperation="Fill"
-                                            DockProperties.DockAdornerHost="{Binding RelativeSource={RelativeSource AncestorType=controls:MdiDocumentControl}}" />
-              </DataTemplate>
-            </ItemsControl.ItemTemplate>
-          </ItemsControl>
+          <Grid>
+            <ItemsControl x:Name="PART_ItemsControl"
+                          Classes="MdiLayoutItems"
+                          IsVisible="{Binding $parent[controls:MdiDocumentControl].HasVisibleDocuments}"
+                          ItemsSource="{Binding VisibleDockables}">
+              <ItemsControl.Styles>
+                <Style Selector="ItemsControl.MdiLayoutItems > ContentPresenter"
+                       x:DataType="dmc:IMdiDocument">
+                  <Setter Property="ZIndex" Value="{Binding MdiZIndex}" />
+                </Style>
+              </ItemsControl.Styles>
+              <ItemsControl.ItemsPanel>
+                <ItemsPanelTemplate>
+                  <controls:MdiLayoutPanel LayoutManager="{Binding $parent[controls:MdiDocumentControl].LayoutManager}" />
+                </ItemsPanelTemplate>
+              </ItemsControl.ItemsPanel>
+              <ItemsControl.ItemTemplate>
+                <DataTemplate DataType="dmc:IMdiDocument">
+                  <controls:MdiDocumentWindow IconTemplate="{Binding $parent[controls:MdiDocumentControl].IconTemplate}"
+                                              HeaderTemplate="{Binding $parent[controls:MdiDocumentControl].HeaderTemplate}"
+                                              ModifiedTemplate="{Binding $parent[controls:MdiDocumentControl].ModifiedTemplate}"
+                                              CloseTemplate="{Binding $parent[controls:MdiDocumentControl].CloseTemplate}"
+                                              CloseButtonTheme="{Binding $parent[controls:MdiDocumentControl].CloseButtonTheme}"
+                                              DocumentContextMenu="{DynamicResource MdiDocumentWindowContextMenu}"
+                                              MdiState="{Binding MdiState}"
+                                              ZIndex="{Binding MdiZIndex}"
+                                              DockProperties.IsDropArea="True"
+                                              DockProperties.IsDockTarget="True"
+                                              DockProperties.ShowDockIndicatorOnly="True"
+                                              DockProperties.IndicatorDockOperation="Fill"
+                                              DockProperties.DockAdornerHost="{Binding RelativeSource={RelativeSource AncestorType=controls:MdiDocumentControl}}" />
+                </DataTemplate>
+              </ItemsControl.ItemTemplate>
+            </ItemsControl>
+
+            <ContentControl x:Name="PART_EmptyContentHost"
+                            Content="{Binding EmptyContent}"
+                            ContentTemplate="{Binding $parent[controls:MdiDocumentControl].EmptyContentTemplate}"
+                            HorizontalContentAlignment="Center"
+                            VerticalContentAlignment="Center"
+                            IsVisible="{Binding !$parent[controls:MdiDocumentControl].HasVisibleDocuments}" />
+          </Grid>
         </Border>
       </ControlTemplate>
     </Setter>

src/Dock.Avalonia/Controls/DocumentControl.axaml.cs

@@ -1,12 +1,16 @@
 // Copyright (c) Wiesław Šoltés. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for details.
+using System;
+using System.Collections.Specialized;
+using System.ComponentModel;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Input;
 using Avalonia.Interactivity;
+using Avalonia.Reactive;
 using Avalonia.Styling;
 using Dock.Model.Core;
 
@@ -42,6 +46,12 @@ public class DocumentControl : TemplatedControl
     public static readonly StyledProperty<IDataTemplate> CloseTemplateProperty = 
         AvaloniaProperty.Register<DocumentControl, IDataTemplate>(nameof(CloseTemplate));
 
+    /// <summary>
+    /// Defines the <see cref="EmptyContentTemplate"/> property.
+    /// </summary>
+    public static readonly StyledProperty<IDataTemplate?> EmptyContentTemplateProperty =
+        AvaloniaProperty.Register<DocumentControl, IDataTemplate?>(nameof(EmptyContentTemplate));
+
     /// <summary>
     /// Define the <see cref="CloseButtonTheme"/> property.
     /// </summary>
@@ -69,6 +79,20 @@ public ControlTheme? CloseButtonTheme
     public static readonly StyledProperty<DocumentTabLayout> TabsLayoutProperty =
         AvaloniaProperty.Register<DocumentControl, DocumentTabLayout>(nameof(TabsLayout));
 
+    /// <summary>
+    /// Defines the <see cref="HasVisibleDockables"/> property.
+    /// </summary>
+    public static readonly DirectProperty<DocumentControl, bool> HasVisibleDockablesProperty =
+        AvaloniaProperty.RegisterDirect<DocumentControl, bool>(
+            nameof(HasVisibleDockables),
+            o => o.HasVisibleDockables);
+
+    private INotifyPropertyChanged? _dockSubscription;
+    private INotifyCollectionChanged? _dockablesSubscription;
+    private IDock? _currentDock;
+    private IDisposable? _dataContextSubscription;
+    private bool _hasVisibleDockables;
+
     /// <summary>
     /// Gets or sets tab icon template.
     /// </summary>
@@ -105,6 +129,15 @@ public IDataTemplate CloseTemplate
         set => SetValue(CloseTemplateProperty, value);
     }
 
+    /// <summary>
+    /// Gets or sets template used to render empty host content.
+    /// </summary>
+    public IDataTemplate? EmptyContentTemplate
+    {
+        get => GetValue(EmptyContentTemplateProperty);
+        set => SetValue(EmptyContentTemplateProperty, value);
+    }
+
     /// <summary>
     /// Gets or sets if this is the currently active dockable.
     /// </summary>
@@ -123,6 +156,15 @@ public DocumentTabLayout TabsLayout
         set => SetValue(TabsLayoutProperty, value);
     }
 
+    /// <summary>
+    /// Gets a value indicating whether the current tabbed host contains visible dockables.
+    /// </summary>
+    public bool HasVisibleDockables
+    {
+        get => _hasVisibleDockables;
+        private set => SetAndRaise(HasVisibleDockablesProperty, ref _hasVisibleDockables, value);
+    }
+
     /// <summary>
     /// Initializes new instance of the <see cref="DocumentControl"/> class.
     /// </summary>
@@ -137,6 +179,21 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
         base.OnAttachedToVisualTree(e);
 
         AddHandler(PointerPressedEvent, PressedHandler, RoutingStrategies.Tunnel);
+
+        _dataContextSubscription = this.GetObservable(DataContextProperty)
+            .Subscribe(new AnonymousObserver<object?>(OnDockChanged));
+    }
+
+    /// <inheritdoc/>
+    protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+    {
+        base.OnDetachedFromVisualTree(e);
+
+        RemoveHandler(PointerPressedEvent, PressedHandler);
+
+        _dataContextSubscription?.Dispose();
+        _dataContextSubscription = null;
+        DetachDockSubscriptions();
     }
 
     private void PressedHandler(object? sender, PointerPressedEventArgs e)
@@ -165,4 +222,86 @@ private void UpdatePseudoClasses(bool isActive)
     {
         PseudoClasses.Set(":active", isActive);
     }
+
+    private void OnDockChanged(object? dataContext)
+    {
+        DetachDockSubscriptions();
+
+        _currentDock = dataContext as IDock;
+        if (_currentDock is null)
+        {
+            HasVisibleDockables = false;
+            return;
+        }
+
+        if (_currentDock is INotifyPropertyChanged propertyChanged)
+        {
+            _dockSubscription = propertyChanged;
+            _dockSubscription.PropertyChanged += DockPropertyChanged;
+        }
+
+        AttachDockablesCollection(_currentDock.VisibleDockables as INotifyCollectionChanged);
+        UpdateHasVisibleDockables();
+    }
+
+    private void DockPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (_currentDock is null)
+        {
+            return;
+        }
+
+        if (e.PropertyName != nameof(IDock.VisibleDockables))
+        {
+            return;
+        }
+
+        AttachDockablesCollection(_currentDock.VisibleDockables as INotifyCollectionChanged);
+        UpdateHasVisibleDockables();
+    }
+
+    private void AttachDockablesCollection(INotifyCollectionChanged? collection)
+    {
+        if (_dockablesSubscription != null)
+        {
+            _dockablesSubscription.CollectionChanged -= DockablesCollectionChanged;
+            _dockablesSubscription = null;
+        }
+
+        if (collection is null)
+        {
+            return;
+        }
+
+        _dockablesSubscription = collection;
+        _dockablesSubscription.CollectionChanged += DockablesCollectionChanged;
+    }
+
+    private void DockablesCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        UpdateHasVisibleDockables();
+    }
+
+    private void UpdateHasVisibleDockables()
+    {
+        HasVisibleDockables = _currentDock?.VisibleDockables?.Count > 0;
+    }
+
+    private void DetachDockSubscriptions()
+    {
+        if (_dockSubscription != null)
+        {
+            _dockSubscription.PropertyChanged -= DockPropertyChanged;
+            _dockSubscription = null;
+        }
+
+        if (_dockablesSubscription != null)
+        {
+            _dockablesSubscription.CollectionChanged -= DockablesCollectionChanged;
+            _dockablesSubscription = null;
+        }
+
+        _currentDock = null;
+        HasVisibleDockables = false;
+    }
 }