completed the branch

src/Shared/HandyControl_Shared/Controls/Slider/CompareSlider/CompareSlider.cs

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+using System.Windows;
+using System.Windows.Controls;
+
+namespace HandyControl.Controls
+{
+    public class CompareSlider : Slider
+    {
+        public static readonly DependencyProperty TargetContentProperty = DependencyProperty.Register(
+            "TargetContent", typeof(object), typeof(CompareSlider), new PropertyMetadata(default(object)));
+
+        public static readonly DependencyProperty SourceContentProperty = DependencyProperty.Register(
+            "SourceContent", typeof(object), typeof(CompareSlider), new PropertyMetadata(default(object)));
+
+        public object TargetContent
+        {
+            get => GetValue(TargetContentProperty);
+            set => SetValue(TargetContentProperty, value);
+        }
+
+        public object SourceContent
+        {
+            get => GetValue(SourceContentProperty);
+            set => SetValue(SourceContentProperty, value);
+        }        
+    }
+}

src/Shared/HandyControl_Shared/Controls/Slider/CompareSlider/CompareTrack.cs

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+using System;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
+
+namespace HandyControl.Controls
+{
+    public class CompareTrack : Track
+    {
+        protected override Size ArrangeOverride(Size arrangeSize)
+        {
+            base.ArrangeOverride(arrangeSize);
+
+            var isVertical = Orientation == Orientation.Vertical;
+            ComputeSliderLengths(arrangeSize, isVertical, out var decreaseButtonLength, out var thumbLength,
+                out var increaseButtonLength);
+
+            var offset = new Point();
+            var pieceSize = arrangeSize;
+            var isDirectionReversed = IsDirectionReversed;
+
+            if (isVertical)
+            {
+                CoerceLength(ref decreaseButtonLength, arrangeSize.Height);
+                CoerceLength(ref increaseButtonLength, arrangeSize.Height);
+                CoerceLength(ref thumbLength, arrangeSize.Height);
+
+                offset.Y = isDirectionReversed ? decreaseButtonLength + thumbLength : 0.0;
+                pieceSize.Height = increaseButtonLength;
+
+                IncreaseRepeatButton?.Arrange(new Rect(offset, pieceSize));
+
+                offset.Y = isDirectionReversed ? 0.0 : increaseButtonLength + thumbLength;
+                pieceSize.Height = decreaseButtonLength;
+
+                if (DecreaseRepeatButton != null)
+                {
+                    DecreaseRepeatButton.Arrange(new Rect(offset, pieceSize));
+                    DecreaseRepeatButton.Height = pieceSize.Height;
+                }
+
+                offset.Y = isDirectionReversed ? decreaseButtonLength : increaseButtonLength;
+                pieceSize.Height = thumbLength;
+
+                Thumb?.Arrange(new Rect(offset, pieceSize));
+            }
+            else
+            {
+                CoerceLength(ref decreaseButtonLength, arrangeSize.Width);
+                CoerceLength(ref increaseButtonLength, arrangeSize.Width);
+                CoerceLength(ref thumbLength, arrangeSize.Width);
+
+                offset.X = isDirectionReversed ? increaseButtonLength + thumbLength : 0.0;
+                pieceSize.Width = decreaseButtonLength;
+
+                DecreaseRepeatButton?.Arrange(new Rect(offset, pieceSize));
+
+
+                offset.X = isDirectionReversed ? 0.0 : decreaseButtonLength + thumbLength;
+                pieceSize.Width = increaseButtonLength;
+
+                if (IncreaseRepeatButton != null)
+                {
+                    IncreaseRepeatButton.Arrange(new Rect(offset, pieceSize));
+                    IncreaseRepeatButton.Width = pieceSize.Width;
+                }
+
+                offset.X = isDirectionReversed ? increaseButtonLength : decreaseButtonLength;
+                pieceSize.Width = thumbLength;
+
+                Thumb?.Arrange(new Rect(offset, pieceSize));
+            }
+
+            return arrangeSize;
+        }
+
+        private void ComputeSliderLengths(Size arrangeSize, bool isVertical, out double decreaseButtonLength,
+            out double thumbLength, out double increaseButtonLength)
+        {
+            var min = Minimum;
+            var range = Math.Max(0.0, Maximum - min);
+            var offset = Math.Min(range, Value - min);
+
+            double trackLength;
+
+            // Compute thumb size
+            if (isVertical)
+            {
+                trackLength = arrangeSize.Height;
+                thumbLength = Thumb?.DesiredSize.Height ?? 0;
+            }
+            else
+            {
+                trackLength = arrangeSize.Width;
+                thumbLength = Thumb?.DesiredSize.Width ?? 0;
+            }
+
+            CoerceLength(ref thumbLength, trackLength);
+
+            var remainingTrackLength = trackLength - thumbLength;
+
+            decreaseButtonLength = remainingTrackLength * offset / range;
+            CoerceLength(ref decreaseButtonLength, remainingTrackLength);
+
+            increaseButtonLength = remainingTrackLength - decreaseButtonLength;
+            CoerceLength(ref increaseButtonLength, remainingTrackLength);
+        }
+
+        private static void CoerceLength(ref double componentLength, double trackLength)
+        {
+            if (componentLength < 0)
+                componentLength = 0.0;
+            else if (componentLength > trackLength || double.IsNaN(componentLength))
+                componentLength = trackLength;
+        }
+    }
+}