added a new AP to SliderAssist to add an eventhandler to the RepeatButtons of the Slider

Author: Corvin Szimion

src/MaterialDesignThemes.Wpf/SliderAssist.cs

@@ -1,4 +1,6 @@
-namespace MaterialDesignThemes.Wpf;
+using System.Windows.Media;
+
+namespace MaterialDesignThemes.Wpf;
 
 public static class SliderAssist
 {
@@ -39,4 +41,46 @@ public static void SetToolTipFormat(RangeBase element, string value)
 
     public static string GetToolTipFormat(RangeBase element)
         => (string)element.GetValue(ToolTipFormatProperty);
+
+    #region Issue3628
+    internal static readonly DependencyProperty FocusParentSliderOnClickProperty =
+            DependencyProperty.RegisterAttached(
+                "FocusParentSliderOnClick",
+                typeof(bool),
+                typeof(SliderAssist),
+                new PropertyMetadata(false, OnFocusParentSliderOnClickChanged));
+
+    internal static bool GetFocusParentSliderOnClick(DependencyObject obj) =>
+        (bool)obj.GetValue(FocusParentSliderOnClickProperty);
+
+    internal static void SetFocusParentSliderOnClick(DependencyObject obj, bool value) =>
+        obj.SetValue(FocusParentSliderOnClickProperty, value);
+
+    private static void OnFocusParentSliderOnClickChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (d is RepeatButton repeatButton)
+        {
+            if ((bool)e.NewValue)
+            {
+                repeatButton.AddHandler(UIElement.PreviewMouseLeftButtonDownEvent,
+                                        (MouseButtonEventHandler)RepeatButton_PreviewMouseLeftButtonDown,
+                                        true);
+            }
+            else
+            {
+                repeatButton.RemoveHandler(UIElement.PreviewMouseLeftButtonDownEvent,
+                                           (MouseButtonEventHandler)RepeatButton_PreviewMouseLeftButtonDown);
+            }
+        }
+    }
+
+    private static void RepeatButton_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
+    {
+        if (sender is DependencyObject repeatButton)
+        {
+            var slider = TreeHelper.FindParent<Slider>(repeatButton);
+            slider?.Focus();
+        }
+    }
+    #endregion
 }

src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Slider.xaml

@@ -17,6 +17,7 @@
     <Setter Property="Focusable" Value="False" />
     <Setter Property="IsTabStop" Value="False" />
     <Setter Property="OverridesDefaultStyle" Value="True" />
+    <Setter Property="wpf:SliderAssist.FocusParentSliderOnClick" Value="True"/>
     <Setter Property="Template">
       <Setter.Value>
         <ControlTemplate TargetType="{x:Type RepeatButton}">
@@ -965,7 +966,7 @@
     <Setter Property="BorderBrush" Value="Transparent" />
     <Setter Property="FocusVisualStyle" Value="{x:Null}" />
     <Setter Property="Foreground" Value="{DynamicResource MaterialDesign.Brush.Primary}" />
-    <Setter Property="IsMoveToPointEnabled" Value="False" />
+    <Setter Property="IsMoveToPointEnabled" Value="True" />
     <Setter Property="SnapsToDevicePixels" Value="False" />
     <Setter Property="Stylus.IsPressAndHoldEnabled" Value="false" />
     <Setter Property="Template" Value="{StaticResource MaterialDesignSliderHorizontal}" />
@@ -985,12 +986,7 @@
     <Setter Property="Background" Value="{x:Null}" />
     <Setter Property="BorderBrush" Value="Transparent" />
     <Setter Property="Foreground" Value="{DynamicResource MaterialDesign.Brush.Primary}" />
-    <!--
-    When IsMoveToPointEnabled is true, additional code is being executed before the actual "base.OnPreviewMouseLeftButtonDown(e);"
-    in which the event is marked as handled, i suspect this is the issue, see:
-    https://source.dot.net/#PresentationFramework/System/Windows/Controls/Slider.cs,771
-    -->
-    <Setter Property="IsMoveToPointEnabled" Value="False" />
+    <Setter Property="IsMoveToPointEnabled" Value="True" />
     <Setter Property="IsSnapToTickEnabled" Value="True" />
     <Setter Property="Orientation" Value="Horizontal" />
     <Setter Property="SnapsToDevicePixels" Value="False" />

src/MaterialDesignThemes.Wpf/TreeHelper.cs

@@ -144,4 +144,22 @@ private static bool IsAncestorTill(FrameworkElement? element, object ancestor, o
         }
         return foundChild;
     }
+
+    public static T FindParent<T>(DependencyObject child) where T : DependencyObject
+    {
+        DependencyObject parentObject = VisualTreeHelper.GetParent(child);
+        if (parentObject is null)
+        {
+            return null!;
+        }
+
+        if (parentObject is T parent)
+        {
+            return parent;
+        }
+        else
+        {
+            return FindParent<T>(parentObject);
+        }
+    }
 }