Dim all but the current section

osu.Game/Overlays/Settings/SettingsSection.cs

@@ -4,9 +4,11 @@
 using System.Collections.Generic;
 using System.Linq;
 using osu.Framework.Allocation;
+using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
+using osu.Framework.Input.Events;
 using osu.Framework.Localisation;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Sprites;
@@ -19,6 +21,10 @@ namespace osu.Game.Overlays.Settings
         protected FillFlowContainer FlowContent;
         protected override Container<Drawable> Content => FlowContent;
 
+        private IBindable<SettingsSection> selectedSection;
+
+        private Container content;
+
         public abstract Drawable CreateIcon();
         public abstract LocalisableString Header { get; }
 
@@ -36,6 +42,9 @@ namespace osu.Game.Overlays.Settings
 
         public bool FilteringActive { get; set; }
 
+        [Resolved]
+        private SettingsPanel settingsPanel { get; set; }
+
         protected SettingsSection()
         {
             Margin = new MarginPadding { Top = margin };
@@ -65,7 +74,7 @@ namespace osu.Game.Overlays.Settings
                     RelativeSizeAxes = Axes.X,
                     Height = border_size,
                 },
-                new Container
+                content = new Container
                 {
                     Padding = new MarginPadding
                     {
@@ -91,6 +100,44 @@ namespace osu.Game.Overlays.Settings
                     }
                 },
             });
+
+            selectedSection = settingsPanel.CurrentSection.GetBoundCopy();
+            selectedSection.BindValueChanged(selected =>
+            {
+                if (selected.NewValue == this)
+                    content.FadeIn(500, Easing.OutQuint);
+                else
+                    content.FadeTo(0.25f, 500, Easing.OutQuint);
+            }, true);
+        }
+
+        private bool isCurrentSection => selectedSection.Value == this;
+
+        protected override bool OnHover(HoverEvent e)
+        {
+            if (!isCurrentSection)
+                content.FadeTo(0.6f, 500, Easing.OutQuint);
+            return base.OnHover(e);
+        }
+
+        protected override void OnHoverLost(HoverLostEvent e)
+        {
+            if (!isCurrentSection)
+                content.FadeTo(0.25f, 500, Easing.OutQuint);
+            base.OnHoverLost(e);
+        }
+
+        protected override bool OnClick(ClickEvent e)
+        {
+            if (!isCurrentSection)
+                settingsPanel.SectionsContainer.ScrollTo(this);
+
+            return base.OnClick(e);
+        }
+
+        protected override bool ShouldBeConsideredForInput(Drawable child)
+        {
+            return isCurrentSection;
         }
     }
 }

osu.Game/Overlays/SettingsPanel.cs

@@ -8,6 +8,7 @@ using System.Threading.Tasks;
 using osuTK;
 using osuTK.Graphics;
 using osu.Framework.Allocation;
+using osu.Framework.Bindables;
 using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
@@ -21,6 +22,7 @@ using osu.Game.Overlays.Settings;
 
 namespace osu.Game.Overlays
 {
+    [Cached]
     public abstract class SettingsPanel : OsuFocusedOverlayContainer
     {
         public const float CONTENT_MARGINS = 15;
@@ -46,7 +48,7 @@ namespace osu.Game.Overlays
         protected Sidebar Sidebar;
         private SidebarButton selectedSidebarButton;
 
-        protected SettingsSectionsContainer SectionsContainer;
+        public SettingsSectionsContainer SectionsContainer { get; private set; }
 
         private SeekLimitedSearchTextBox searchTextBox;
 
@@ -65,6 +67,8 @@ namespace osu.Game.Overlays
 
         private Task sectionsLoadingTask;
 
+        public IBindable<SettingsSection> CurrentSection = new Bindable<SettingsSection>();
+
         protected SettingsPanel(bool showSidebar)
         {
             this.showSidebar = showSidebar;
@@ -105,6 +109,7 @@ namespace osu.Game.Overlays
                 Masking = true,
                 RelativeSizeAxes = Axes.Both,
                 ExpandableHeader = CreateHeader(),
+                SelectedSection = { BindTarget = CurrentSection },
                 FixedHeader = searchTextBox = new SeekLimitedSearchTextBox
                 {
                     RelativeSizeAxes = Axes.X,
@@ -238,7 +243,9 @@ namespace osu.Game.Overlays
                     if (selectedSidebarButton != null)
                         selectedSidebarButton.Selected = false;
 
-                    selectedSidebarButton = Sidebar.Children.Single(b => b.Section == section.NewValue);
+                    selectedSidebarButton = Sidebar.Children.FirstOrDefault(b => b.Section == section.NewValue);
+
+                    if (selectedSidebarButton != null)
                         selectedSidebarButton.Selected = true;
                 }, true);
             });