feat:Redesign the usage pattern of WHAnimationHelper once more to deliver a superior axaml editing and consumption experience.

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

@@ -1,5 +1,11 @@
-using Avalonia.Controls;
+using System;
+using Avalonia;
+using Avalonia.Animation;
+using Avalonia.Animation.Easings;
+using Avalonia.Controls;
 using Avalonia.Interactivity;
+using Avalonia.Layout;
+using Avalonia.Styling;
 using Ursa.Controls;
 using Ursa.Helpers;
 
@@ -7,17 +13,42 @@ namespace Ursa.Demo.Pages;
 
 public partial class NavMenuDemo : UserControl
 {
-    private readonly NavMenuAnimationHelper _animationHelper;
-
     public NavMenuDemo()
     {
         InitializeComponent();
-        _animationHelper = new NavMenuAnimationHelper(menu);
     }
 
-    protected override void OnLoaded(RoutedEventArgs e)
-    {
-        base.OnLoaded(e);
-        _animationHelper.Start();
-    }
+    public static WHAnimationHelperCreateAnimationDelegate NavMenuAnimation { get; } =
+        (_, oldDesiredSize, newDesiredSize) =>
+        {
+            if (oldDesiredSize.Width > newDesiredSize.Width)
+                newDesiredSize = newDesiredSize.WithWidth(newDesiredSize.Width + 20);
+            return new Animation
+            {
+                Duration = TimeSpan.FromMilliseconds(300),
+                Easing = new CubicEaseInOut(),
+                FillMode = FillMode.None,
+                Children =
+                {
+                    new KeyFrame
+                    {
+                        Cue = new Cue(0.0),
+                        Setters =
+                        {
+                            new Setter(WidthProperty, oldDesiredSize.Width),
+                            new Setter(HeightProperty, oldDesiredSize.Height)
+                        }
+                    },
+                    new KeyFrame
+                    {
+                        Cue = new Cue(1.0),
+                        Setters =
+                        {
+                            new Setter(WidthProperty, newDesiredSize.Width),
+                            new Setter(HeightProperty, newDesiredSize.Height)
+                        }
+                    }
+                }
+            };
+        };
 }