feat: setup demo.

demo/Ursa.Demo/Models/MenuKeys.cs

@@ -6,6 +6,7 @@ public static class MenuKeys
     public const string MenuKeyBadge = "Badge";
     public const string MenuKeyBanner = "Banner";
     public const string MenuKeyButtonGroup = "ButtonGroup";
+    public const string MenuKeyDialog = "Dialog";
     public const string MenuKeyDivider = "Divider";
     public const string MenuKeyDualBadge = "DualBadge";
     public const string MenuKeyImageViewer = "ImageViewer";

demo/Ursa.Demo/Pages/DialogDemo.axaml

@@ -0,0 +1,29 @@
+<UserControl
+    x:Class="Ursa.Demo.Pages.DialogDemo"
+    xmlns="https://github.com/avaloniaui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:u="https://irihi.tech/ursa"
+    xmlns:vm="using:Ursa.Demo.ViewModels"
+    d:DesignHeight="450"
+    d:DesignWidth="800"
+    x:CompileBindings="True"
+    x:DataType="vm:DialogDemoViewModel"
+    mc:Ignorable="d">
+    <Grid ColumnDefinitions="Auto, *">
+        <StackPanel Grid.Column="0">
+            <Button Command="{Binding ShowLocalOverlayDialogCommand}">Show Local Overlay Dialog</Button>
+            <Button Command="{Binding ShowGlobalOverlayDialogCommand}"> Show Global Overlay Dialog </Button>
+        </StackPanel>
+        <Grid Grid.Column="1">
+            <Button
+                HorizontalAlignment="Center"
+                VerticalAlignment="Center"
+                Command="{Binding ShowLocalOverlayDialogCommand}">
+                Show Local Overlay Dialog
+            </Button>
+            <u:OverlayDialogHost HostId="LocalHost" />
+        </Grid>
+    </Grid>
+</UserControl>

demo/Ursa.Demo/Pages/DialogDemo.axaml.cs

@@ -0,0 +1,13 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace Ursa.Demo.Pages;
+
+public partial class DialogDemo : UserControl
+{
+    public DialogDemo()
+    {
+        InitializeComponent();
+    }
+}

demo/Ursa.Demo/ViewModels/DialogDemoViewModel.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Windows.Input;
+using Avalonia.Controls;
+using Avalonia.Controls.Shapes;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Ursa.Controls;
+
+namespace Ursa.Demo.ViewModels;
+
+public class DialogDemoViewModel: ObservableObject
+{
+    public ICommand ShowLocalOverlayDialogCommand { get; }
+    public ICommand ShowGlobalOverlayDialogCommand { get; }
+
+    public DialogDemoViewModel()
+    {
+        ShowLocalOverlayDialogCommand = new RelayCommand(ShowLocalOverlayDialog);
+        ShowGlobalOverlayDialogCommand = new RelayCommand(ShowGlobalOverlayDialog);
+    }
+
+    private async void ShowGlobalOverlayDialog()
+    {
+        await DialogBox.ShowOverlayAsync<Banner, DateTime>(DateTime.Now, "GlobalHost");
+    }
+
+    private async void ShowLocalOverlayDialog()
+    {
+        await DialogBox.ShowOverlayAsync<Banner, DateTime>(DateTime.Now, "LocalHost");
+    }
+}

demo/Ursa.Demo/ViewModels/MainViewViewModel.cs

@@ -28,6 +28,7 @@ public class MainViewViewModel : ViewModelBase
             MenuKeys.MenuKeyBadge => new BadgeDemoViewModel(),
             MenuKeys.MenuKeyBanner => new BannerDemoViewModel(),
             MenuKeys.MenuKeyButtonGroup => new ButtonGroupDemoViewModel(),
+            MenuKeys.MenuKeyDialog => new DialogDemoViewModel(),
             MenuKeys.MenuKeyDivider => new DividerDemoViewModel(),
             MenuKeys.MenuKeyDualBadge => new DualBadgeDemoViewModel(),
             MenuKeys.MenuKeyImageViewer => new ImageViewerDemoViewModel(),

demo/Ursa.Demo/ViewModels/MenuViewModel.cs

@@ -15,6 +15,7 @@ public class MenuViewModel: ViewModelBase
             new() { MenuHeader = "Badge", Key = MenuKeys.MenuKeyBadge },
             new() { MenuHeader = "Banner", Key = MenuKeys.MenuKeyBanner },
             new() { MenuHeader = "ButtonGroup", Key = MenuKeys.MenuKeyButtonGroup },
+            new() { MenuHeader = "Dialog", Key = MenuKeys.MenuKeyDialog },
             new() { MenuHeader = "Divider", Key = MenuKeys.MenuKeyDivider },
             new() { MenuHeader = "DualBadge", Key = MenuKeys.MenuKeyDualBadge },
             new() { MenuHeader = "IconButton", Key = MenuKeys.MenuKeyIconButton },

demo/Ursa.Demo/Views/MainView.axaml

@@ -80,6 +80,7 @@
                 <converters:ViewLocator />
             </ContentControl.ContentTemplate>
         </ContentControl>
+        <u:OverlayDialogHost Grid.Row="0" Grid.Column="0" Grid.RowSpan="2" Grid.ColumnSpan="2" HostId="GlobalHost" />
     </Grid>
 
 </UserControl>

src/Ursa/Controls/Dialog/DialogBox.cs

@@ -1,4 +1,7 @@
+using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Controls.Shapes;
+using Avalonia.Media;
 
 namespace Ursa.Controls;
 
@@ -15,6 +18,20 @@ public static class DialogBox
     {
         TView t = new TView();
         t.DataContext = vm;
-        return;
+    }
+
+    public static async Task<object?> ShowOverlayAsync<TView, TViewModel>(TViewModel vm, string hostId)
+        where TView : Control, new()
+        where TViewModel: new()
+    {
+        var t = new Border()
+        {
+            Width = 100, Height = 100, Background = Brushes.Aqua, BorderBrush = Brushes.Yellow,
+            BorderThickness = new Thickness(1)
+        };
+        t.DataContext = vm;
+        var host = OverlayDialogManager.GetOverlayDialogHost(hostId);
+        host?.Children.Add(t);
+        return null;
     }
 }

src/Ursa/Controls/Dialog/OverlayDialogHost.cs

@@ -2,18 +2,40 @@ using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
+using Avalonia.Media;
 using Avalonia.Utilities;
 
 namespace Ursa.Controls;
 
-public class DialogHost: Canvas
+public class OverlayDialogHost: Canvas
 {
+    public static readonly StyledProperty<string> HostIdProperty = AvaloniaProperty.Register<OverlayDialogHost, string>(
+        nameof(HostId));
+
+    public string HostId
+    {
+        get => GetValue(HostIdProperty);
+        set => SetValue(HostIdProperty, value);
+    }
+    
     private Point _lastPoint;
     
+    protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+    {
+        base.OnAttachedToVisualTree(e);
+        OverlayDialogManager.RegisterOverlayDialogHost(this, HostId);
+    }
+
+    protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+    {
+        OverlayDialogManager.UnregisterOverlayDialogHost(HostId);
+        base.OnDetachedFromVisualTree(e);
+    }
+
     protected override void OnPointerMoved(PointerEventArgs e)
     {
         base.OnPointerMoved(e);
-        if (e.Source is DialogControl item)
+        if (e.Source is Control item)
         {
             if (e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
             {
@@ -31,7 +53,7 @@ public class DialogHost: Canvas
     protected override void OnPointerPressed(PointerPressedEventArgs e)
     {
         base.OnPointerPressed(e);
-        if (e.Source is DialogControl item)
+        if (e.Source is Control item)
         {
             _lastPoint = e.GetPosition(item);
         }

src/Ursa/Controls/Dialog/OverlayDialogManager.cs

@@ -0,0 +1,23 @@
+using System.Collections.Concurrent;
+
+namespace Ursa.Controls;
+
+internal static class OverlayDialogManager
+{
+    private static ConcurrentDictionary<string, OverlayDialogHost> _hosts = new();
+    
+    public static void RegisterOverlayDialogHost(OverlayDialogHost host, string id)
+    {
+        _hosts.TryAdd(id, host);
+    }
+    
+    public static void UnregisterOverlayDialogHost(string id)
+    {
+        _hosts.TryRemove(id, out _);
+    }
+    
+    public static OverlayDialogHost? GetOverlayDialogHost(string id)
+    {
+        return _hosts.TryGetValue(id, out var host) ? host : null;
+    }
+}