added easing functions

Demos/EasingsDemo.cs

@@ -0,0 +1,54 @@
+using System.Linq;
+using System.Reflection;
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using MLEM.Extensions;
+using MLEM.Misc;
+using MLEM.Startup;
+using MLEM.Ui;
+using MLEM.Ui.Elements;
+
+namespace Demos {
+    public class EasingsDemo : Demo {
+
+        private static readonly FieldInfo[] EasingFields = typeof(Easings)
+            .GetFields(BindingFlags.Public | BindingFlags.Static).ToArray();
+        private static readonly Easings.Easing[] Easings = EasingFields
+            .Select(f => (Easings.Easing) f.GetValue(null)).ToArray();
+        private Group group;
+        private int current;
+
+        public EasingsDemo(MlemGame game) : base(game) {
+        }
+
+        public override void LoadContent() {
+            base.LoadContent();
+
+            this.group = new Group(Anchor.TopCenter, Vector2.One) {SetWidthBasedOnChildren = true};
+            this.group.AddChild(new Button(Anchor.AutoCenter, new Vector2(30, 10), "Next") {
+                OnPressed = e => this.current = (this.current + 1) % Easings.Length
+            });
+            this.group.AddChild(new Paragraph(Anchor.AutoCenter, 1, p => EasingFields[this.current].Name, true));
+            this.UiSystem.Get("DemoUi").Element.AddChild(this.group);
+        }
+
+        public override void Clear() {
+            this.group.Parent.RemoveChild(this.group);
+        }
+
+        public override void DoDraw(GameTime time) {
+            this.GraphicsDevice.Clear(Color.CornflowerBlue);
+            base.DoDraw(time);
+
+            this.SpriteBatch.Begin(SpriteSortMode.Deferred, null, SamplerState.PointClamp);
+            var view = this.GraphicsDevice.Viewport;
+            var easing = Easings[this.current].ScaleInput(0, view.Width).ScaleOutput(-view.Height / 3, view.Height / 3);
+            for (var x = 0; x < view.Width; x++) {
+                var area = new RectangleF(x - 2, view.Height / 2 - easing(x) - 2, 4, 4);
+                this.SpriteBatch.Draw(this.SpriteBatch.GetBlankTexture(), area, Color.Green);
+            }
+            this.SpriteBatch.End();
+        }
+
+    }
+}

Demos/GameImpl.cs

@@ -24,6 +24,7 @@ namespace Demos {
             Demos.Add("Animation and Texture Atlas", ("An example of UniformTextureAtlases, SpriteAnimations and SpriteAnimationGroups", game => new AnimationDemo(game)));
             Demos.Add("Auto Tiling", ("A demonstration of the AutoTiling class that MLEM provides", game => new AutoTilingDemo(game)));
             Demos.Add("Pathfinding", ("An example of MLEM's A* pathfinding implementation in 2D", game => new PathfindingDemo(game)));
+            Demos.Add("Easings", ("An example of MLEM's Easings class, an adaptation of easings.net", game => new EasingsDemo(game)));
         }
 
         public GameImpl() {

MLEM/Misc/Easings.cs

@@ -0,0 +1,110 @@
+using System;
+
+namespace MLEM.Misc {
+    /// <summary>
+    /// This class contains a set of easing functions, adapted from <see href="https://easings.net"/>.
+    /// These can be used for ui elements or any other kind of animations.
+    /// By default, each function takes an input that ranges between 0 and 1, and produces an output that roughly ranges between 0 and 1. To change this behavior, you can use <see cref="ScaleInput"/> and <see cref="ScaleOutput"/>.
+    /// </summary>
+    public static class Easings {
+
+        /// <summary><see href="https://easings.net/#easeInSine"/></summary>
+        public static readonly Easing InSine = p => 1 - (float) Math.Cos(p * Math.PI / 2);
+        /// <summary><see href="https://easings.net/#easeOutSine"/></summary>
+        public static readonly Easing OutSine = p => (float) Math.Sin(p * Math.PI / 2);
+        /// <summary><see href="https://easings.net/#easeInOutSine"/></summary>
+        public static readonly Easing InOutSine = p => -((float) Math.Cos(p * Math.PI) - 1) / 2;
+
+        /// <summary><see href="https://easings.net/#easeInQuad"/></summary>
+        public static readonly Easing InQuad = p => p * p;
+        /// <summary><see href="https://easings.net/#easeOutQuad"/></summary>
+        public static readonly Easing OutQuad = p => 1 - (1 - p) * (1 - p);
+        /// <summary><see href="https://easings.net/#easeInOutQuad"/></summary>
+        public static readonly Easing InOutQuad = p => p < 0.5F ? 2 * p * p : 1 - (-2 * p + 2) * (-2 * p + 2) / 2;
+
+        /// <summary><see href="https://easings.net/#easeInCubic"/></summary>
+        public static readonly Easing InCubic = p => p * p * p;
+        /// <summary><see href="https://easings.net/#easeOutCubic"/></summary>
+        public static readonly Easing OutCubic = p => 1 - (1 - p) * (1 - p) * (1 - p);
+        /// <summary><see href="https://easings.net/#easeInOutCubic"/></summary>
+        public static readonly Easing InOutCubic = p => p < 0.5F ? 4 * p * p * p : 1 - (-2 * p + 2) * (-2 * p + 2) * (-2 * p + 2) / 2;
+
+        /// <summary><see href="https://easings.net/#easeInExpo"/></summary>
+        public static readonly Easing InExpo = p => p == 0 ? 0 : (float) Math.Pow(2, 10 * p - 10);
+        /// <summary><see href="https://easings.net/#easeOutExpo"/></summary>
+        public static readonly Easing OutExpo = p => p == 1 ? 1 : 1 - (float) Math.Pow(2, -10 * p);
+        /// <summary><see href="https://easings.net/#easeInOutExpo"/></summary>
+        public static readonly Easing InOutExpo = p => p == 0 ? 0 : p == 1 ? 1 : p < 0.5F ? (float) Math.Pow(2, 20 * p - 10) / 2 : (2 - (float) Math.Pow(2, -20 * p + 10)) / 2;
+
+        /// <summary><see href="https://easings.net/#easeInCirc"/></summary>
+        public static readonly Easing InCirc = p => 1 - (float) Math.Sqrt(1 - p * p);
+        /// <summary><see href="https://easings.net/#easeOutCirc"/></summary>
+        public static readonly Easing OutCirc = p => (float) Math.Sqrt(1 - (p - 1) * (p - 1));
+        /// <summary><see href="https://easings.net/#easeInOutCirc"/></summary>
+        public static readonly Easing InOutCirc = p => p < 0.5F ? (1 - (float) Math.Sqrt(1 - 2 * p * (2 * p))) / 2 : ((float) Math.Sqrt(1 - (-2 * p + 2) * (-2 * p + 2)) + 1) / 2;
+
+        /// <summary><see href="https://easings.net/#easeInBack"/></summary>
+        public static readonly Easing InBack = p => 2.70158F * p * p * p - 1.70158F * p * p;
+        /// <summary><see href="https://easings.net/#easeOutBack"/></summary>
+        public static readonly Easing OutBack = p => 1 + 2.70158F * (p - 1) * (p - 1) * (p - 1) + 1.70158F * (p - 1) * (p - 1);
+        /// <summary><see href="https://easings.net/#easeInOutBack"/></summary>
+        public static readonly Easing InOutBack = p => p < 0.5 ? 2 * p * (2 * p) * ((2.594909F + 1) * 2 * p - 2.594909F) / 2 : ((2 * p - 2) * (2 * p - 2) * ((2.594909F + 1) * (p * 2 - 2) + 2.594909F) + 2) / 2;
+
+        /// <summary><see href="https://easings.net/#easeInElastic"/></summary>
+        public static readonly Easing InElastic = p => p == 0 ? 0 : p == 1 ? 1 : -(float) Math.Pow(2, 10 * p - 10) * (float) Math.Sin((p * 10 - 10.75) * 2.094395F);
+        /// <summary><see href="https://easings.net/#easeOutElastic"/></summary>
+        public static readonly Easing OutElastic = p => p == 0 ? 0 : p == 1 ? 1 : (float) Math.Pow(2, -10 * p) * (float) Math.Sin((p * 10 - 0.75) * 2.0943951023932F) + 1;
+        /// <summary><see href="https://easings.net/#easeInOutElastic"/></summary>
+        public static readonly Easing InOutElastic = p => p == 0 ? 0 : p == 1 ? 1 : p < 0.5 ? -((float) Math.Pow(2, 20 * p - 10) * (float) Math.Sin((20 * p - 11.125) * 1.39626340159546F)) / 2 : (float) Math.Pow(2, -20 * p + 10) * (float) Math.Sin((20 * p - 11.125) * 1.39626340159546F) / 2 + 1;
+
+        /// <summary><see href="https://easings.net/#easeInBounce"/></summary>
+        public static readonly Easing InBounce = p => 1 - OutBounce(1 - p);
+        /// <summary><see href="https://easings.net/#easeOutBounce"/></summary>
+        public static readonly Easing OutBounce = p => {
+            const float n1 = 7.5625F;
+            const float d1 = 2.75F;
+            if (p < 1 / d1) {
+                return n1 * p * p;
+            } else if (p < 2 / d1) {
+                return n1 * (p -= 1.5F / d1) * p + 0.75F;
+            } else if (p < 2.5 / d1) {
+                return n1 * (p -= 2.25F / d1) * p + 0.9375F;
+            } else {
+                return n1 * (p -= 2.625F / d1) * p + 0.984375F;
+            }
+        };
+        /// <summary><see href="https://easings.net/#easeInOutBounce"/></summary>
+        public static readonly Easing InOutBounce = p => p < 0.5 ? (1 - OutBounce(1 - 2 * p)) / 2 : (1 + OutBounce(2 * p - 1)) / 2;
+
+        /// <summary>
+        /// Scales the input of an easing function, which is usually between 0 and 1, to a given minimum and maximum.
+        /// Note that the minimum needs to be smaller than the maximum.
+        /// </summary>
+        /// <param name="easing">The easing function to scale</param>
+        /// <param name="min">The minimum input value</param>
+        /// <param name="max">The maximum input value</param>
+        /// <returns>The scaled easing function</returns>
+        public static Easing ScaleInput(this Easing easing, float min, float max) {
+            return p => easing((p - min) / (max - min));
+        }
+
+        /// <summary>
+        /// Scales the output of an easing function, which is usually between 0 and 1, to a given minimum and maximum.
+        /// Note that the minimum needs to be smaller than the maximum.
+        /// </summary>
+        /// <param name="easing">The easing function to scale</param>
+        /// <param name="min">The minimum output value</param>
+        /// <param name="max">The maximum output value</param>
+        /// <returns>The scaled easing function</returns>
+        public static Easing ScaleOutput(this Easing easing, float min, float max) {
+            return p => easing(p) * (max - min) + min;
+        }
+
+        /// <summary>
+        /// A delegate method used by <see cref="Easings"/>.
+        /// </summary>
+        /// <param name="percentage">The percentage into the easing function. Either between 0 and 1, or, if <see cref="Easings.ScaleInput"/> was used, between an arbitary set of values.</param>
+        public delegate float Easing(float percentage);
+
+    }
+}