Add support for right mouse absolute scrolling (when enabled)

Will likely need to be bindable when hooked up to settings and actually used.

osu.Game/Graphics/Containers/OsuScrollContainer.cs

@@ -0,0 +1,72 @@
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Input;
+using OpenTK.Input;
+
+namespace osu.Game.Graphics.Containers
+{
+    class OsuScrollContainer : ScrollContainer
+    {
+        /// <summary>
+        /// Add the ability to seek to an absolute scroll position when the right mouse button is pressed or dragged.
+        /// Uses the value of <see cref="DistanceDecayOnRightMouseScrollbar"/> to smoothly scroll to the dragged location.
+        /// </summary>
+        public bool RightMouseScrollbar = false;
+
+        /// <summary>
+        /// Controls the rate with which the target position is approached when performing a relative drag. Default is 0.02.
+        /// </summary>
+        public double DistanceDecayOnRightMouseScrollbar = 0.02;
+
+        private bool shouldPerformRelativeDrag(InputState state) => RightMouseScrollbar && state.Mouse.IsPressed(MouseButton.Right);
+
+        private void scrollToRelative(float value) => ScrollTo(Clamp((value - Scrollbar.DrawSize[ScrollDim] / 2) / Scrollbar.Size[ScrollDim]), true, DistanceDecayOnRightMouseScrollbar);
+
+        private bool mouseScrollBarDragging;
+
+        protected override bool IsDragging => base.IsDragging || mouseScrollBarDragging;
+
+        protected override bool OnMouseDown(InputState state, MouseDownEventArgs args)
+        {
+            if (shouldPerformRelativeDrag(state))
+            {
+                scrollToRelative(state.Mouse.Position[ScrollDim]);
+                return true;
+            }
+
+            return base.OnMouseDown(state, args);
+        }
+
+        protected override bool OnDrag(InputState state)
+        {
+            if (mouseScrollBarDragging)
+            {
+                scrollToRelative(state.Mouse.Position[ScrollDim]);
+                return true;
+            }
+
+            return base.OnDrag(state);
+        }
+
+        protected override bool OnDragStart(InputState state)
+        {
+            if (shouldPerformRelativeDrag(state))
+            {
+                mouseScrollBarDragging = true;
+                return true;
+            }
+
+            return base.OnDragStart(state);
+        }
+
+        protected override bool OnDragEnd(InputState state)
+        {
+            if (mouseScrollBarDragging)
+            {
+                mouseScrollBarDragging = false;
+                return true;
+            }
+
+            return base.OnDragEnd(state);
+        }
+    }
+}

osu.Game/Graphics/Containers/SectionsContainer.cs

@@ -114,7 +114,7 @@ namespace osu.Game.Graphics.Containers
 
         public SectionsContainer()
         {
-            Add(ScrollContainer = new ScrollContainer()
+            Add(ScrollContainer = new OsuScrollContainer()
             {
                 RelativeSizeAxes = Axes.Both,
                 Masking = false,

osu.Game/Overlays/Chat/ChannelSelectionOverlay.cs

@@ -81,7 +81,7 @@ namespace osu.Game.Overlays.Chat
                     Padding = new MarginPadding { Top = 85, Right = WIDTH_PADDING },
                     Children = new[]
                     {
-                        new ScrollContainer
+                        new OsuScrollContainer
                         {
                             RelativeSizeAxes = Axes.Both,
                             Children = new[]

osu.Game/Overlays/Chat/DrawableChannel.cs

@@ -7,6 +7,7 @@ using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
+using osu.Game.Graphics.Containers;
 using osu.Game.Online.Chat;
 
 namespace osu.Game.Overlays.Chat
@@ -25,7 +26,7 @@ namespace osu.Game.Overlays.Chat
 
             Children = new Drawable[]
             {
-                scroll = new ScrollContainer
+                scroll = new OsuScrollContainer
                 {
                     RelativeSizeAxes = Axes.Both,
                     Children = new Drawable[]

osu.Game/Overlays/Music/PlaylistList.cs

@@ -7,6 +7,7 @@ using System.Linq;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Game.Database;
+using osu.Game.Graphics.Containers;
 
 namespace osu.Game.Overlays.Music
 {
@@ -49,7 +50,7 @@ namespace osu.Game.Overlays.Music
         {
             Children = new Drawable[]
             {
-                new ScrollContainer
+                new OsuScrollContainer
                 {
                     RelativeSizeAxes = Axes.Both,
                     Children = new Drawable[]

osu.Game/Overlays/NotificationManager.cs

@@ -36,7 +36,7 @@ namespace osu.Game.Overlays
                     Colour = Color4.Black,
                     Alpha = 0.6f,
                 },
-                scrollContainer = new ScrollContainer
+                scrollContainer = new OsuScrollContainer
                 {
                     RelativeSizeAxes = Axes.Both,
                     Margin = new MarginPadding { Top = Toolbar.Toolbar.HEIGHT },

osu.Game/Overlays/SearchableList/SearchableListOverlay.cs

@@ -7,6 +7,7 @@ using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Input;
 using osu.Game.Graphics.Backgrounds;
+using osu.Game.Graphics.Containers;
 
 namespace osu.Game.Overlays.SearchableList
 {
@@ -60,7 +61,7 @@ namespace osu.Game.Overlays.SearchableList
                     RelativeSizeAxes = Axes.Both,
                     Children = new[]
                     {
-                        new ScrollContainer
+                        new OsuScrollContainer
                         {
                             RelativeSizeAxes = Axes.Both,
                             ScrollbarVisible = false,

osu.Game/Screens/Multiplayer/RoomInspector.cs

@@ -17,6 +17,7 @@ using osu.Framework.Localisation;
 using osu.Game.Beatmaps.Drawables;
 using osu.Game.Database;
 using osu.Game.Graphics;
+using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.Sprites;
 using osu.Game.Online.Multiplayer;
 using osu.Game.Users;
@@ -341,7 +342,7 @@ namespace osu.Game.Screens.Multiplayer
                         },
                     },
                 },
-                participantsScroll = new ScrollContainer
+                participantsScroll = new OsuScrollContainer
                 {
                     Anchor = Anchor.BottomLeft,
                     Origin = Anchor.BottomLeft,

osu.Game/Screens/Select/Leaderboards/Leaderboard.cs

@@ -12,6 +12,7 @@ using System;
 using osu.Framework.Allocation;
 using osu.Framework.Threading;
 using osu.Game.Database;
+using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Rulesets.Scoring;
 using osu.Game.Online.API;
@@ -74,7 +75,7 @@ namespace osu.Game.Screens.Select.Leaderboards
         {
             Children = new Drawable[]
             {
-                scrollContainer = new ScrollContainer
+                scrollContainer = new OsuScrollContainer
                 {
                     RelativeSizeAxes = Axes.Both,
                     ScrollbarVisible = false,

osu.Game/osu.Game.csproj

@@ -78,6 +78,7 @@
     <Compile Include="Beatmaps\DifficultyCalculator.cs" />
     <Compile Include="Graphics\Containers\OsuClickableContainer.cs" />
     <Compile Include="Graphics\Containers\OsuFocusedOverlayContainer.cs" />
+    <Compile Include="Graphics\Containers\OsuScrollContainer.cs" />
     <Compile Include="Graphics\Cursor\OsuContextMenuContainer.cs" />
     <Compile Include="Graphics\UserInterface\IconButton.cs" />
     <Compile Include="Configuration\SelectionRandomType.cs" />