Tidy up button hierarchy

osu.Game/Graphics/UserInterface/OsuAnimatedButton.cs

@@ -0,0 +1,109 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Framework.Allocation;
+using osu.Framework.Extensions.Color4Extensions;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Shapes;
+using osu.Framework.Input;
+using osu.Game.Graphics.Containers;
+using OpenTK.Graphics;
+
+namespace osu.Game.Graphics.UserInterface
+{
+    /// <summary>
+    /// Highlight on hover, bounce on click.
+    /// </summary>
+    public class OsuAnimatedButton : OsuClickableContainer
+    {
+        /// <summary>
+        /// The colour that should be flashed when the <see cref="IconButton"/> is clicked.
+        /// </summary>
+        protected Color4 FlashColour = Color4.White.Opacity(0.3f);
+
+        private Color4 hoverColour = Color4.White.Opacity(0.1f);
+
+        /// <summary>
+        /// The background colour of the <see cref="IconButton"/> while it is hovered.
+        /// </summary>
+        protected Color4 HoverColour
+        {
+            get => hoverColour;
+            set
+            {
+                hoverColour = value;
+                hover.Colour = value;
+            }
+        }
+
+        protected override Container<Drawable> Content => content;
+
+        private readonly Container content;
+        private readonly Box hover;
+
+        public OsuAnimatedButton()
+        {
+            base.Content.Add(content = new Container
+            {
+                Origin = Anchor.Centre,
+                Anchor = Anchor.Centre,
+                RelativeSizeAxes = Axes.Both,
+                CornerRadius = 5,
+                Masking = true,
+                EdgeEffect = new EdgeEffectParameters
+                {
+                    Colour = Color4.Black.Opacity(0.04f),
+                    Type = EdgeEffectType.Shadow,
+                    Radius = 5,
+                },
+                Children = new Drawable[]
+                {
+                    hover = new Box
+                    {
+                        RelativeSizeAxes = Axes.Both,
+                        Colour = HoverColour,
+                        Blending = BlendingMode.Additive,
+                        Alpha = 0,
+                    },
+                }
+            });
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(OsuColour colours)
+        {
+            Enabled.BindValueChanged(enabled => this.FadeColour(enabled ? Color4.White : colours.Gray9, 200, Easing.OutQuint), true);
+        }
+
+        protected override bool OnHover(InputState state)
+        {
+            hover.FadeIn(500, Easing.OutQuint);
+            return base.OnHover(state);
+        }
+
+        protected override void OnHoverLost(InputState state)
+        {
+            hover.FadeOut(500, Easing.OutQuint);
+            base.OnHoverLost(state);
+        }
+
+        protected override bool OnClick(InputState state)
+        {
+            hover.FlashColour(FlashColour, 800, Easing.OutQuint);
+            return base.OnClick(state);
+        }
+
+        protected override bool OnMouseDown(InputState state, MouseDownEventArgs args)
+        {
+            Content.ScaleTo(0.75f, 2000, Easing.OutQuint);
+            return base.OnMouseDown(state, args);
+        }
+
+        protected override bool OnMouseUp(InputState state, MouseUpEventArgs args)
+        {
+            Content.ScaleTo(1, 1000, Easing.OutElastic);
+            return base.OnMouseUp(state, args);
+        }
+    }
+}