feat: refactor dialog host to accept drawer.

src/Ursa/Controls/OverlayShared/OverlayFeedbackElement.cs

@@ -0,0 +1,78 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.Threading;
+using Ursa.EventArgs;
+
+namespace Ursa.Controls.OverlayShared;
+
+public abstract class OverlayFeedbackElement: ContentControl
+{
+    static OverlayFeedbackElement()
+    {
+        DataContextProperty.Changed.AddClassHandler<CustomDialogControl, object?>((o, e) => o.OnDataContextChange(e));
+    }
+    
+    public static readonly RoutedEvent<ResultEventArgs> ClosedEvent = RoutedEvent.Register<DrawerControlBase, ResultEventArgs>(
+        nameof(Closed), RoutingStrategies.Bubble);
+    
+    public event EventHandler<ResultEventArgs> Closed
+    {
+        add => AddHandler(ClosedEvent, value);
+        remove => RemoveHandler(ClosedEvent, value);
+    }
+    
+    private void OnDataContextChange(AvaloniaPropertyChangedEventArgs<object?> args)
+    {
+        if (args.OldValue.Value is IDialogContext oldContext)
+        {
+            oldContext.RequestClose -= OnContextRequestClose;
+        }
+        if (args.NewValue.Value is IDialogContext newContext)
+        {
+            newContext.RequestClose += OnContextRequestClose;
+        }
+    }
+    
+    protected virtual void OnElementClosing(object sender, object? args)
+    {
+        RaiseEvent(new ResultEventArgs(ClosedEvent, args));
+    }
+    
+    private void OnContextRequestClose(object sender, object? args)
+    {
+        RaiseEvent(new ResultEventArgs(ClosedEvent, args));
+    }
+    
+    public Task<T?> ShowAsync<T>(CancellationToken? token = default)
+    { 
+        var tcs = new TaskCompletionSource<T?>();
+        token?.Register(() =>
+        {
+            Dispatcher.UIThread.Invoke(Close);
+        });
+        
+        void OnCloseHandler(object sender, ResultEventArgs? args)
+        {
+            if (args?.Result is T result)
+            {
+                tcs.SetResult(result);
+            }
+            else
+            {
+                tcs.SetResult(default);
+            }
+            RemoveHandler(ClosedEvent, OnCloseHandler);
+        }
+
+        AddHandler(ClosedEvent, OnCloseHandler);
+        return tcs.Task;
+    }
+    
+    protected static void SetVisibility(Button? button, bool visible)
+    {
+        if (button is not null) button.IsVisible = visible;
+    }
+    
+    public abstract void Close();
+}