Implement MarkerPart for the marker

osu.Game/Screens/Edit/Components/Timelines/Summary/Parts/MarkerPart.cs

@@ -0,0 +1,108 @@
+using OpenTK;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Shapes;
+using osu.Framework.Input;
+using osu.Game.Beatmaps;
+using osu.Game.Graphics;
+
+namespace osu.Game.Screens.Edit.Components.Timelines.Summary.Parts
+{
+    /// <summary>
+    /// The part of the timeline that displays the current position of the song.
+    /// </summary>
+    internal class MarkerPart : TimelinePart
+    {
+        private WorkingBeatmap beatmap;
+
+        private readonly Drawable marker;
+
+        public MarkerPart()
+        {
+            Add(marker = new MarkerVisualisation());
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(OsuColour colours)
+        {
+            marker.Colour = colours.Red;
+        }
+
+        protected override void LoadBeatmap(WorkingBeatmap beatmap)
+        {
+            this.beatmap = beatmap;
+        }
+
+        protected override bool OnDragStart(InputState state) => true;
+        protected override bool OnDragEnd(InputState state) => true;
+        protected override bool OnDrag(InputState state)
+        {
+            seekToPosition(state.Mouse.NativeState.Position);
+            return true;
+        }
+
+        protected override bool OnMouseDown(InputState state, MouseDownEventArgs args)
+        {
+            seekToPosition(state.Mouse.NativeState.Position);
+            return true;
+        }
+
+        /// <summary>
+        /// Seeks the <see cref="SummaryTimeline"/> to the time closest to a position on the screen relative to the <see cref="SummaryTimeline"/>.
+        /// </summary>
+        /// <param name="screenPosition">The position in screen coordinates.</param>
+        private void seekToPosition(Vector2 screenPosition)
+        {
+            float markerPos = MathHelper.Clamp(ToLocalSpace(screenPosition).X, 0, DrawWidth);
+            seekTo(markerPos / DrawWidth * beatmap.Track.Length);
+        }
+
+        private void seekTo(double time) => beatmap.Track.Seek(time);
+
+        protected override void Update()
+        {
+            base.Update();
+            marker.X = (float)beatmap.Track.CurrentTime;
+        }
+
+        private class MarkerVisualisation : CompositeDrawable
+        {
+            public MarkerVisualisation()
+            {
+                Anchor = Anchor.CentreLeft;
+                Origin = Anchor.Centre;
+                RelativePositionAxes = Axes.X;
+                RelativeSizeAxes = Axes.Y;
+                AutoSizeAxes = Axes.X;
+                InternalChildren = new Drawable[]
+                {
+                        new Triangle
+                        {
+                            Anchor = Anchor.TopCentre,
+                            Origin = Anchor.BottomCentre,
+                            Scale = new Vector2(1, -1),
+                            Size = new Vector2(10, 5),
+                        },
+                        new Triangle
+                        {
+                            Anchor = Anchor.BottomCentre,
+                            Origin = Anchor.BottomCentre,
+                            Size = new Vector2(10, 5)
+                        },
+                        new Box
+                        {
+                            Anchor = Anchor.Centre,
+                            Origin = Anchor.Centre,
+                            RelativeSizeAxes = Axes.Y,
+                            Width = 2,
+                            EdgeSmoothness = new Vector2(1, 0)
+                        }
+                };
+            }
+
+            [BackgroundDependencyLoader]
+            private void load(OsuColour colours) => Colour = colours.Red;
+        }
+    }
+}

osu.Game/osu.Game.csproj

@@ -609,6 +609,7 @@
     <Compile Include="Screens\Edit\Components\Timelines\Summary\Parts\BreakPart.cs" />
     <Compile Include="Screens\Edit\Components\Timelines\Summary\Parts\BookmarkPart.cs" />
     <Compile Include="Screens\Edit\Components\Timelines\Summary\Parts\ControlPointPart.cs" />
+    <Compile Include="Screens\Edit\Components\Timelines\Summary\Parts\MarkerPart.cs" />
     <Compile Include="Screens\Edit\Components\Timelines\Summary\Parts\TimelinePart.cs" />
     <Compile Include="Screens\Edit\Components\Timelines\Summary\Visualisations\DurationVisualisation.cs" />
     <Compile Include="Screens\Edit\Components\Timelines\Summary\Visualisations\PointVisualisation.cs" />