add new API for Track for controls that handles their own dragging logic.

src/Avalonia.Controls/Primitives/Track.cs

@@ -41,13 +41,16 @@ namespace Avalonia.Controls.Primitives
         public static readonly StyledProperty<bool> IsDirectionReversedProperty =
             AvaloniaProperty.Register<Track, bool>(nameof(IsDirectionReversed));
 
+        public static readonly StyledProperty<bool> IgnoreThumbDragProperty =
+            AvaloniaProperty.Register<Track, bool>(nameof(IsThumbDragHandled));
+
         private double _minimum;
         private double _maximum = 100.0;
         private double _value;
 
         static Track()
         {
-            ThumbProperty.Changed.AddClassHandler<Track>((x,e) => x.ThumbChanged(e));
+            ThumbProperty.Changed.AddClassHandler<Track>((x, e) => x.ThumbChanged(e));
             IncreaseButtonProperty.Changed.AddClassHandler<Track>((x, e) => x.ButtonChanged(e));
             DecreaseButtonProperty.Changed.AddClassHandler<Track>((x, e) => x.ButtonChanged(e));
             AffectsArrange<Track>(MinimumProperty, MaximumProperty, ValueProperty, OrientationProperty);
@@ -113,6 +116,12 @@ namespace Avalonia.Controls.Primitives
             set { SetValue(IsDirectionReversedProperty, value); }
         }
 
+        public bool IsThumbDragHandled
+        {
+            get { return GetValue(IgnoreThumbDragProperty); }
+            set { SetValue(IgnoreThumbDragProperty, value); }
+        }
+
         private double ThumbCenterOffset { get; set; }
         private double Density { get; set; }
 
@@ -422,6 +431,9 @@ namespace Avalonia.Controls.Primitives
 
         private void ThumbDragged(object sender, VectorEventArgs e)
         {
+            if (IsThumbDragHandled)
+                return;
+                
             Value = MathUtilities.Clamp(
                 Value + ValueFromDistance(e.Vector.X, e.Vector.Y),
                 Minimum,

src/Avalonia.Controls/Slider.cs

@@ -103,7 +103,7 @@ namespace Avalonia.Controls
 
             if (_track != null)
             {
-                _track.Thumb.IsHitTestVisible = false;
+                _track.IsThumbDragHandled = true;
             }
 
             if (_decreaseButton != null)