Implement CommentsHeader component

osu.Game/Overlays/Comments/HeaderButton.cs

@@ -0,0 +1,72 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Allocation;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Shapes;
+using osu.Game.Graphics;
+using osu.Framework.Input.Events;
+using osu.Game.Graphics.UserInterface;
+
+namespace osu.Game.Overlays.Comments
+{
+    public class HeaderButton : Container
+    {
+        private const int height = 20;
+        private const int corner_radius = 3;
+        private const int margin = 10;
+        private const int duration = 200;
+
+        protected override Container<Drawable> Content => content;
+
+        private readonly Box background;
+        private readonly Container content;
+
+        public HeaderButton()
+        {
+            AutoSizeAxes = Axes.X;
+            Height = height;
+            Masking = true;
+            CornerRadius = corner_radius;
+            AddRangeInternal(new Drawable[]
+            {
+                background = new Box
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    Alpha = 0,
+                },
+                content = new Container
+                {
+                    AutoSizeAxes = Axes.Both,
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre,
+                    Margin = new MarginPadding { Horizontal = margin }
+                },
+                new HoverClickSounds(),
+            });
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(OsuColour colours)
+        {
+            background.Colour = colours.Gray4;
+        }
+
+        protected override bool OnHover(HoverEvent e)
+        {
+            FadeInBackground();
+            return base.OnHover(e);
+        }
+
+        protected override void OnHoverLost(HoverLostEvent e)
+        {
+            base.OnHoverLost(e);
+            FadeOutBackground();
+        }
+
+        protected void FadeInBackground() => background.FadeIn(duration, Easing.OutQuint);
+
+        protected void FadeOutBackground() => background.FadeOut(duration, Easing.OutQuint);
+    }
+}