Add rounded button variant

osu.Game/Graphics/UserInterfaceV2/RoundedButton.cs

@@ -0,0 +1,48 @@
+// 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;
+using osu.Framework.Graphics.Effects;
+using osu.Game.Graphics.UserInterface;
+using osuTK;
+
+namespace osu.Game.Graphics.UserInterfaceV2
+{
+    public class RoundedButton : OsuButton
+    {
+        public override float Height
+        {
+            get => base.Height;
+            set
+            {
+                base.Height = value;
+
+                if (IsLoaded)
+                    updateCornerRadius();
+            }
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(OsuColour colours)
+        {
+            BackgroundColour = colours.Blue3;
+
+            Content.EdgeEffect = new EdgeEffectParameters
+            {
+                Type = EdgeEffectType.Shadow,
+                Offset = new Vector2(0, 2),
+                Radius = 4,
+                Colour = Colour4.Black.Opacity(0.15f)
+            };
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+            updateCornerRadius();
+        }
+
+        private void updateCornerRadius() => Content.CornerRadius = DrawHeight / 2;
+    }
+}