From 78f5855b870e7fff311fe0ecbe3d70964887ae08 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wies=C5=82aw=20=C5=A0olt=C3=A9s?= <wieslaw.soltes@gmail.com>
Date: Mon, 19 Sep 2022 20:31:32 +0200
Subject: [PATCH] Add spring easing

---
 .../Animation/Easings/SpringEasing.cs         | 80 +++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 src/Avalonia.Base/Animation/Easings/SpringEasing.cs

diff --git a/src/Avalonia.Base/Animation/Easings/SpringEasing.cs b/src/Avalonia.Base/Animation/Easings/SpringEasing.cs
new file mode 100644
index 0000000000..70e74c639f
--- /dev/null
+++ b/src/Avalonia.Base/Animation/Easings/SpringEasing.cs
@@ -0,0 +1,80 @@
+namespace Avalonia.Animation.Easings;
+
+/// <summary>
+/// Eases a <see cref="double"/> value using a user-defined spring formula.
+/// </summary>
+public class SpringEasing : Easing
+{
+    private readonly Spring _internalSpring;
+
+    /// <summary>
+    /// The spring mass.
+    /// </summary>
+    public double Mass
+    {
+        get => _internalSpring.Mass;
+        set
+        {
+            _internalSpring.Mass = value;
+        }
+    }
+
+    /// <summary>
+    /// The spring stiffness.
+    /// </summary>
+    public double Stiffness
+    {
+        get => _internalSpring.Stiffness;
+        set
+        {
+            _internalSpring.Stiffness = value;
+        }
+    }
+
+    /// <summary>
+    /// The spring damping.
+    /// </summary> 
+    public double Damping
+    {
+        get => _internalSpring.Damping;
+        set
+        {
+            _internalSpring.Damping = value;
+        }
+    }
+
+    /// <summary>
+    /// The spring initial velocity.
+    /// </summary>
+    public double InitialVelocity
+    {
+        get => _internalSpring.InitialVelocity;
+        set
+        {
+            _internalSpring.InitialVelocity = value;
+        }
+    }
+
+    public SpringEasing(double mass = 0d, double stiffness = 0d, double damping = 0d, double initialVelocity = 0d)
+    {
+        _internalSpring = new Spring();
+
+        Mass = mass;
+        Stiffness = stiffness;
+        Damping = damping;
+        InitialVelocity = initialVelocity;
+    }
+
+    public SpringEasing(Spring keySpline)
+    {
+        _internalSpring = keySpline;
+    }
+    
+    public SpringEasing()
+    {
+        _internalSpring = new Spring();
+    }
+
+    /// <inheritdoc/>
+    public override double Ease(double progress) => _internalSpring.GetSpringProgress(progress);
+}