Add ability to render frosted sliders

osu.Game.Rulesets.Osu/Skinning/Default/DrawableSliderPath.cs

@@ -2,18 +2,24 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using osu.Framework.Graphics.Lines;
+using osuTK;
 using osuTK.Graphics;
 
 namespace osu.Game.Rulesets.Osu.Skinning.Default
 {
-    public abstract partial class DrawableSliderPath : SmoothPath
+    public abstract partial class DrawableSliderPath : BackdropBlurPath
     {
         public const float BORDER_PORTION = 0.128f;
         public const float GRADIENT_PORTION = 1 - BORDER_PORTION;
 
         private const float border_max_size = 8f;
         private const float border_min_size = 0f;
 
+        protected DrawableSliderPath()
+        {
+            EffectBufferScale = new Vector2(0.25f);
+        }
+
         private Color4 borderColour = Color4.White;
 
         public Color4 BorderColour

osu.Game.Rulesets.Osu/Skinning/Legacy/LegacyMainCirclePiece.cs

@@ -74,6 +74,7 @@ private void load()
                 {
                     Anchor = Anchor.Centre,
                     Origin = Anchor.Centre,
+                    Alpha = priorityLookupPrefix == null ? 0.75f : 0.5f // TODO: this is kind of a dirty way to check if we're a hitcircle or a circle that's part of a slider.
                 },
                 OverlayLayer = new Container
                 {

osu.Game.Rulesets.Osu/Skinning/Legacy/LegacySliderBody.cs

@@ -7,6 +7,7 @@
 using osu.Game.Rulesets.Osu.Skinning.Default;
 using osu.Game.Skinning;
 using osu.Game.Utils;
+using osuTK;
 using osuTK.Graphics;
 
 namespace osu.Game.Rulesets.Osu.Skinning.Legacy
@@ -18,11 +19,21 @@ public partial class LegacySliderBody : PlaySliderBody
         protected override Color4 GetBodyAccentColour(ISkinSource skin, Color4 hitObjectAccentColour)
         {
             // legacy skins use a constant value for slider track alpha, regardless of the source colour.
-            return base.GetBodyAccentColour(skin, hitObjectAccentColour).Opacity(0.7f);
+            return base.GetBodyAccentColour(skin, hitObjectAccentColour).Opacity(0.6f);
         }
 
         private partial class LegacyDrawableSliderPath : DrawableSliderPath
         {
+            public LegacyDrawableSliderPath()
+            {
+                BlurSigma = new Vector2(16f);
+
+                BackdropTintStrength = 0.5f;
+
+                // To prevent shadows from contributing to the background blur effect
+                MaskCutoff = 0.25f;
+            }
+
             protected override Color4 ColourAt(float position)
             {
                 // https://github.com/peppy/osu-stable-reference/blob/3ea48705eb67172c430371dcfc8a16a002ed0d3d/osu!/Graphics/Renderers/MmSliderRendererGL.cs#L99

osu.Game/OsuGame.cs

@@ -994,7 +994,11 @@
                             Children = new Drawable[]
                             {
                                 backReceptor = new ScreenFooter.BackReceptor(),
-                                ScreenStack = new OsuScreenStack { RelativeSizeAxes = Axes.Both },
+                                new RefCountedBackbufferProvider
+                                {
+                                    RelativeSizeAxes = Axes.Both,
+                                    Child = ScreenStack = new OsuScreenStack { RelativeSizeAxes = Axes.Both }
+                                },
                                 BackButton = new BackButton(backReceptor)
                                 {
                                     Anchor = Anchor.BottomLeft,