From 0161bfbeec544ad0c3dd0fcde2183fc1655013c7 Mon Sep 17 00:00:00 2001
From: punker76 <punkerat76@gmail.com>
Date: Thu, 12 Dec 2019 15:30:20 +0100
Subject: [PATCH] Add new attached property
 TreeViewItemHelper.ToggleButtonStyle

Add this new attached property to make it possible to set the inner ToggleButton style. The default is `MahApps.Styles.ToggleButton.ExpandCollapse`.
---
 .../Controls/Helper/TreeViewItemHelper.cs     | 36 +++++++++++++++++++
 .../Styles/Controls.TreeView.xaml             |  9 +++--
 2 files changed, 42 insertions(+), 3 deletions(-)
 create mode 100644 src/MahApps.Metro/Controls/Helper/TreeViewItemHelper.cs

diff --git a/src/MahApps.Metro/Controls/Helper/TreeViewItemHelper.cs b/src/MahApps.Metro/Controls/Helper/TreeViewItemHelper.cs
new file mode 100644
index 0000000000..ef30eea9be
--- /dev/null
+++ b/src/MahApps.Metro/Controls/Helper/TreeViewItemHelper.cs
@@ -0,0 +1,36 @@
+using System.ComponentModel;
+using System.Windows;
+using System.Windows.Controls;
+
+namespace MahApps.Metro.Controls
+{
+    public static class TreeViewItemHelper
+    {
+        public static readonly DependencyProperty ToggleButtonStyleProperty
+            = DependencyProperty.RegisterAttached(
+                "ToggleButtonStyle",
+                typeof(Style),
+                typeof(TreeViewItemHelper),
+                new FrameworkPropertyMetadata((Style)null, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure));
+
+        /// <summary>
+        /// Gets the toggle button style used for the TreeViewItem expander.
+        /// </summary>
+        [Category(AppName.MahApps)]
+        [AttachedPropertyBrowsableForType(typeof(TreeViewItem))]
+        public static Style GetToggleButtonStyle(UIElement element)
+        {
+            return (Style)element.GetValue(ToggleButtonStyleProperty);
+        }
+
+        /// <summary>
+        /// Sets the toggle button style used for the TreeViewItem expander.
+        /// </summary>
+        [Category(AppName.MahApps)]
+        [AttachedPropertyBrowsableForType(typeof(TreeViewItem))]
+        public static void SetToggleButtonStyle(UIElement element, Style value)
+        {
+            element.SetValue(ToggleButtonStyleProperty, value);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/MahApps.Metro/Styles/Controls.TreeView.xaml b/src/MahApps.Metro/Styles/Controls.TreeView.xaml
index dc0dd266bc..fc53e4bd56 100644
--- a/src/MahApps.Metro/Styles/Controls.TreeView.xaml
+++ b/src/MahApps.Metro/Styles/Controls.TreeView.xaml
@@ -15,6 +15,7 @@
         <Setter Property="Foreground" Value="{DynamicResource MahApps.Brushes.Black}" />
         <Setter Property="Height" Value="16" />
         <Setter Property="Margin" Value="1" />
+        <Setter Property="MinWidth" Value="19" />
         <Setter Property="Template">
             <Setter.Value>
                 <ControlTemplate TargetType="{x:Type ToggleButton}">
@@ -77,6 +78,7 @@
         <Setter Property="Controls:ItemHelper.HoverSelectedBackgroundBrush" Value="{DynamicResource MahApps.Brushes.Accent}" />
         <Setter Property="Controls:ItemHelper.SelectedBackgroundBrush" Value="{DynamicResource MahApps.Brushes.Accent2}" />
         <Setter Property="Controls:ItemHelper.SelectedForegroundBrush" Value="{DynamicResource MahApps.Brushes.AccentSelectedColor}" />
+        <Setter Property="Controls:TreeViewItemHelper.ToggleButtonStyle" Value="{StaticResource MahApps.Styles.ToggleButton.ExpandCollapse}" />
         <Setter Property="FocusVisualStyle" Value="{x:Null}" />
         <Setter Property="Foreground" Value="{DynamicResource MahApps.Brushes.Text}" />
         <Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, Mode=OneWay, FallbackValue=Stretch, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
@@ -97,13 +99,14 @@
                                   VerticalAlignment="Stretch"
                                   Background="Transparent">
                                 <Grid.ColumnDefinitions>
-                                    <ColumnDefinition Width="Auto" MinWidth="19" />
+                                    <ColumnDefinition Width="Auto" />
                                     <ColumnDefinition Width="*" />
                                 </Grid.ColumnDefinitions>
                                 <ToggleButton x:Name="Expander"
+                                              Grid.Column="0"
                                               ClickMode="Press"
                                               IsChecked="{Binding Path=IsExpanded, RelativeSource={x:Static RelativeSource.TemplatedParent}, Mode=TwoWay}"
-                                              Style="{StaticResource MahApps.Styles.ToggleButton.ExpandCollapse}" />
+                                              Style="{TemplateBinding Controls:TreeViewItemHelper.ToggleButtonStyle}" />
                                 <ContentPresenter x:Name="PART_Header"
                                                   Grid.Column="1"
                                                   HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
@@ -188,7 +191,7 @@
         <!--  default to 0  -->
         <Setter Property="BorderThickness" Value="0" />
         <Setter Property="HorizontalContentAlignment" Value="Stretch" />
-        <Setter Property="Padding" Value="1" />
+        <Setter Property="Padding" Value="0" />
         <Setter Property="SnapsToDevicePixels" Value="True" />
         <Setter Property="Template">
             <Setter.Value>