Moving assist to be on the slider itself

This allow fixes it when the slider has a background color, or the user clicks on the ticks above/below the track

src/MaterialDesignThemes.Wpf/SliderAssist.cs

@@ -23,64 +23,62 @@ public static readonly DependencyProperty OnlyShowFocusVisualWhileDraggingProper
             typeof(SliderAssist),
             new PropertyMetadata(false));
 
-    public static void SetOnlyShowFocusVisualWhileDragging(RangeBase element, bool value)
-        => element.SetValue(OnlyShowFocusVisualWhileDraggingProperty, value);
-
     public static bool GetOnlyShowFocusVisualWhileDragging(RangeBase element)
         => (bool)element.GetValue(OnlyShowFocusVisualWhileDraggingProperty);
 
+    public static void SetOnlyShowFocusVisualWhileDragging(RangeBase element, bool value)
+        => element.SetValue(OnlyShowFocusVisualWhileDraggingProperty, value);
+
     public static readonly DependencyProperty ToolTipFormatProperty
         = DependencyProperty.RegisterAttached(
             "ToolTipFormat",
             typeof(string),
             typeof(SliderAssist),
             new PropertyMetadata(null));
 
-    public static void SetToolTipFormat(RangeBase element, string value)
-        => element.SetValue(ToolTipFormatProperty, value);
-
     public static string GetToolTipFormat(RangeBase element)
         => (string)element.GetValue(ToolTipFormatProperty);
 
-    #region Issue3628
-    internal static readonly DependencyProperty FocusParentSliderOnClickProperty =
+    public static void SetToolTipFormat(RangeBase element, string value)
+        => element.SetValue(ToolTipFormatProperty, value);
+
+    // Fix for Issue3628
+    public static readonly DependencyProperty FocusSliderOnClickProperty =
             DependencyProperty.RegisterAttached(
-                "FocusParentSliderOnClick",
+                "FocusSliderOnClick",
                 typeof(bool),
                 typeof(SliderAssist),
-                new PropertyMetadata(false, OnFocusParentSliderOnClickChanged));
+                new PropertyMetadata(false, OnFocusSliderOnClickChanged));
 
-    internal static bool GetFocusParentSliderOnClick(DependencyObject obj) =>
-        (bool)obj.GetValue(FocusParentSliderOnClickProperty);
+    public static bool GetFocusSliderOnClick(RangeBase obj) =>
+        (bool)obj.GetValue(FocusSliderOnClickProperty);
 
-    internal static void SetFocusParentSliderOnClick(DependencyObject obj, bool value) =>
-        obj.SetValue(FocusParentSliderOnClickProperty, value);
+    public static void SetFocusSliderOnClick(RangeBase obj, bool value) =>
+        obj.SetValue(FocusSliderOnClickProperty, value);
 
-    private static void OnFocusParentSliderOnClickChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    private static void OnFocusSliderOnClickChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
     {
-        if (d is RepeatButton repeatButton)
+        if (d is Slider slider)
         {
             if ((bool)e.NewValue)
             {
-                repeatButton.AddHandler(UIElement.PreviewMouseLeftButtonDownEvent,
-                                        (MouseButtonEventHandler)RepeatButton_PreviewMouseLeftButtonDown,
+                slider.AddHandler(UIElement.PreviewMouseLeftButtonDownEvent,
+                                 (MouseButtonEventHandler)Slider_PreviewMouseLeftButtonDown,
                                         true);
             }
             else
             {
-                repeatButton.RemoveHandler(UIElement.PreviewMouseLeftButtonDownEvent,
-                                           (MouseButtonEventHandler)RepeatButton_PreviewMouseLeftButtonDown);
+                slider.RemoveHandler(UIElement.PreviewMouseLeftButtonDownEvent,
+                                    (MouseButtonEventHandler)Slider_PreviewMouseLeftButtonDown);
             }
         }
     }
 
-    private static void RepeatButton_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
+    private static void Slider_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
     {
-        if (sender is DependencyObject repeatButton)
+        if (sender is Slider slider)
         {
-            var slider = TreeHelper.FindParent<Slider>(repeatButton);
-            slider?.Focus();
+            slider.Focus();
         }
     }
-    #endregion
 }

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

@@ -1,4 +1,4 @@
-<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                     xmlns:converters="clr-namespace:MaterialDesignThemes.Wpf.Converters"
                     xmlns:wpf="clr-namespace:MaterialDesignThemes.Wpf">
@@ -17,7 +17,6 @@
     <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}">
@@ -994,6 +993,7 @@
     <Setter Property="Template" Value="{StaticResource MaterialDesignDiscreteSliderHorizontal}" />
     <Setter Property="UseLayoutRounding" Value="False" />
     <Setter Property="wpf:ElevationAssist.Elevation" Value="Dp1" />
+    <Setter Property="wpf:SliderAssist.FocusSliderOnClick" Value="True" />
     <Style.Triggers>
       <Trigger Property="IsEnabled" Value="False">
         <Setter Property="Foreground" Value="{DynamicResource MaterialDesign.Brush.CheckBox.Disabled}" />
@@ -1016,6 +1016,7 @@
     <Setter Property="Template" Value="{StaticResource MaterialDesignDiscreteSliderVertical}" />
     <Setter Property="UseLayoutRounding" Value="False" />
     <Setter Property="wpf:ElevationAssist.Elevation" Value="Dp1" />
+    <Setter Property="wpf:SliderAssist.FocusSliderOnClick" Value="True" />
     <Style.Triggers>
       <Trigger Property="IsEnabled" Value="False">
         <Setter Property="Foreground" Value="{DynamicResource MaterialDesign.Brush.CheckBox.Disabled}" />

src/MaterialDesignThemes.Wpf/TreeHelper.cs

@@ -144,22 +144,4 @@ 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);
-        }
-    }
 }