feat: implement layer change.

src/Ursa.Themes.Semi/Controls/Dialog.axaml

@@ -26,11 +26,6 @@
                                 Grid.Column="0"
                                 Grid.ColumnSpan="2"
                                 Background="Transparent" >
-                                <Panel.ContextFlyout>
-                                    <MenuFlyout>
-                                        <MenuItem Header="Bring to Top"></MenuItem>
-                                    </MenuFlyout>
-                                </Panel.ContextFlyout>
                             </Panel>
                             <TextBlock
                                 Grid.Column="0"
@@ -55,6 +50,16 @@
             <Setter Property="Grid.Row" Value="0" />
             <Setter Property="Grid.RowSpan" Value="3" />
         </Style>
+        <Style Selector="^:not(:modal) /template/ Panel#PART_TitleArea">
+            <Setter Property="ContextFlyout">
+                <MenuFlyout>
+                    <MenuItem Header="Bring Forward" Command="{Binding $parent[u:DialogControl].BringForward}"></MenuItem>
+                    <MenuItem Header="Send Backward" Command="{Binding $parent[u:DialogControl].SendBackward}" ></MenuItem>
+                    <MenuItem Header="Bring To Front" Command="{Binding $parent[u:DialogControl].BringToFront}"></MenuItem>
+                    <MenuItem Header="Send To Back" Command="{Binding $parent[u:DialogControl].SendToBack}"></MenuItem>
+                </MenuFlyout>
+            </Setter>
+        </Style>
     </ControlTheme>
 
     <ControlTheme x:Key="{x:Type u:DialogWindow}" TargetType="u:DialogWindow">

src/Ursa/Controls/Dialog/DialogBox.cs

@@ -97,6 +97,8 @@ public static class DialogBox
         {
             Content = new TView() { DataContext = vm },
             DataContext = vm,
+            ExtendToClientArea = options.ExtendToClientArea,
+            Title = options.Title,
         };
         var host = OverlayDialogManager.GetOverlayDialogHost(hostId);
         host?.AddModalDialog(t);

src/Ursa/Controls/Dialog/DialogControl.cs

@@ -15,10 +15,12 @@ public class DialogControl: ContentControl
     public const string PART_CloseButton = "PART_CloseButton";
     public const string PART_TitleArea = "PART_TitleArea";
     public const string PC_ExtendClientArea = ":extend";
+    public const string PC_Modal = ":modal";
     
     private Button? _closeButton;
     private Panel? _titleArea;
     public event EventHandler<object?>? OnClose;
+    public event EventHandler<DialogLayerChangeEventArgs>? OnLayerChange;
 
     public static readonly StyledProperty<string?> TitleProperty = AvaloniaProperty.Register<DialogControl, string?>(
         nameof(Title));
@@ -93,7 +95,7 @@ public class DialogControl: ContentControl
     public Task<T> ShowAsync<T>()
     {
         var tcs = new TaskCompletionSource<T>();
-
+        PseudoClasses.Set(PC_Modal, true);
         void OnCloseHandler(object sender, object? args)
         {
             if (args is T result)
@@ -124,4 +126,24 @@ public class DialogControl: ContentControl
             OnClose?.Invoke(this, null);
         }
     }
+
+    public void BringForward()
+    {
+        OnLayerChange?.Invoke(this, new DialogLayerChangeEventArgs(DialogLayerChangeType.BringForward));
+    }
+
+    public void SendBackward()
+    {
+        OnLayerChange?.Invoke(this, new DialogLayerChangeEventArgs(DialogLayerChangeType.SendBackward));
+    } 
+    
+    public void BringToFront()
+    {
+        OnLayerChange?.Invoke(this, new DialogLayerChangeEventArgs(DialogLayerChangeType.BringToFront));
+    }
+    
+    public void SendToBack()
+    {
+        OnLayerChange?.Invoke(this, new DialogLayerChangeEventArgs(DialogLayerChangeType.SendToBack));
+    }
 }

src/Ursa/Controls/Dialog/DialogLayerChangeEventArgs.cs

@@ -0,0 +1,18 @@
+namespace Ursa.Controls;
+
+public class DialogLayerChangeEventArgs
+{
+    public DialogLayerChangeType ChangeType { get; }
+    public DialogLayerChangeEventArgs(DialogLayerChangeType type)
+    {
+        ChangeType = type;
+    }
+}
+
+public enum DialogLayerChangeType
+{
+    BringForward,
+    SendBackward,
+    BringToFront,
+    SendToBack
+}

src/Ursa/Controls/Dialog/OverlayDialogHost.cs

@@ -21,7 +21,8 @@ public class OverlayDialogHost: Canvas
 
     private Point _lastPoint;
 
-    public static readonly StyledProperty<IBrush?> OverlayMaskBrushProperty = AvaloniaProperty.Register<OverlayDialogHost, IBrush?>(
+    public static readonly StyledProperty<IBrush?> OverlayMaskBrushProperty =
+        AvaloniaProperty.Register<OverlayDialogHost, IBrush?>(
             nameof(OverlayMaskBrush));
 
     public IBrush? OverlayMaskBrush
@@ -93,7 +94,9 @@ public class OverlayDialogHost: Canvas
     {
         this.Children.Add(control);
         _dialogs.Add(control);
+        control.ZIndex = Children.Last().ZIndex + 1;
         control.OnClose += OnDialogClose;
+        control.OnLayerChange += OnDialogLayerChange;
     }
 
     private void OnDialogClose(object sender, object? e)
@@ -102,6 +105,7 @@ public class OverlayDialogHost: Canvas
         {
             this.Children.Remove(control);
             control.OnClose -= OnDialogClose;
+            control.OnLayerChange -= OnDialogLayerChange;
             if (_dialogs.Contains(control))
             {
                 _dialogs.Remove(control);
@@ -133,7 +137,41 @@ public class OverlayDialogHost: Canvas
         {
             _masks[i].IsVisible = false;
         }
+
         _masks.Add(mask);
         control.OnClose += OnDialogClose;
+        control.OnLayerChange += OnDialogLayerChange;
+    }
+
+    private void OnDialogLayerChange(object sender, DialogLayerChangeEventArgs e)
+    {
+        if (sender is not DialogControl control)
+            return;
+        if (!_dialogs.Contains(control))
+            return;
+        int index = _dialogs.IndexOf(control);
+        _dialogs.Remove(control);
+        int newIndex = index;
+        switch (e.ChangeType)
+        {
+            case DialogLayerChangeType.BringForward:
+                newIndex = MathUtilities.Clamp(index + 1, 0, _dialogs.Count);
+                break;
+            case DialogLayerChangeType.SendBackward:
+                newIndex = MathUtilities.Clamp(index - 1, 0, _dialogs.Count);
+                break;
+            case DialogLayerChangeType.BringToFront:
+                newIndex = _dialogs.Count;
+                break;
+            case DialogLayerChangeType.SendToBack:
+                newIndex = 0;
+                break;
+        }
+
+        _dialogs.Insert(newIndex, control);
+        for (int i = 0; i < _dialogs.Count; i++)
+        {
+            _dialogs[i].ZIndex = i;
+        }
     }
 }