Add double variant for Spring class (#6706)

* Add double variant for spring class

* Fix precedence implicit brackets

---------

Co-authored-by: marvin <m.schuerz@hautzy.com>
Co-authored-by: Dean Herbert <pe@ppy.sh>

Author: 3 people

osu.Framework/Graphics/Transforms/Spring.cs

@@ -117,10 +117,18 @@ public T Update(double elapsed, T target, T? targetVelocity = null)
 
         protected void ComputeSingleValue(float dt, ref float current, ref float velocity, float target, float targetVelocity)
         {
-            float k2Stable = MathF.Max(MathF.Max(k2, dt * dt / 2 + dt * k1 / 2), dt * k1);
+            float k2Stable = MathF.Max(MathF.Max(k2, (dt * dt) / 2 + (dt * k1) / 2), dt * k1);
 
             current += dt * velocity;
-            velocity += (dt * (target + k3 * targetVelocity - current - k1 * velocity)) / k2Stable;
+            velocity += (dt * (target + (k3 * targetVelocity) - current - (k1 * velocity))) / k2Stable;
+        }
+
+        protected void ComputeSingleValue(float dt, ref double current, ref double velocity, double target, double targetVelocity)
+        {
+            float k2Stable = MathF.Max(MathF.Max(k2, (dt * dt) / 2 + (dt * k1) / 2), dt * k1);
+
+            current += dt * velocity;
+            velocity += (dt * (target + (k3 * targetVelocity) - current - (k1 * velocity))) / k2Stable;
         }
     }
 
@@ -136,6 +144,18 @@ protected override float ComputeNextValue(float dt, float target, float targetVe
         }
     }
 
+    public class DoubleSpring : Spring<double>
+    {
+        protected override double GetTargetVelocity(double target, double previousTarget, float dt) => (target - previousTarget) / dt;
+
+        protected override double ComputeNextValue(float dt, double target, double targetVelocity)
+        {
+            ComputeSingleValue(dt, ref Current, ref Velocity, target, targetVelocity);
+
+            return Current;
+        }
+    }
+
     public class Vector2Spring : Spring<Vector2>
     {
         protected override Vector2 GetTargetVelocity(Vector2 target, Vector2 previousTarget, float dt) => (target - previousTarget) / dt;