[Win] Variants

8 files changed, 309 insertions, 11 deletions

diff --git a/Xamarin.PropertyEditing.Windows/BoolsToVisibilityConverter.cs b/Xamarin.PropertyEditing.Windows/BoolsToVisibilityConverter.cs
index 9923ddd..770ac2b 100644
--- a/Xamarin.PropertyEditing.Windows/BoolsToVisibilityConverter.cs
+++ b/Xamarin.PropertyEditing.Windows/BoolsToVisibilityConverter.cs
@@ -10,15 +10,15 @@ namespace Xamarin.PropertyEditing.Windows
 	{
 		public object Convert (object[] values, Type targetType, object parameter, CultureInfo culture)
 		{
-			bool value = false;
 			if (values != null) {
-				value = (bool)values[0];
-				for (int i = 1; i < values.Length; i++) {
-					value = value && (bool)values[i];
+				for (int i = 0; i < values.Length; i++) {
+					object v = values[i];
+					if (v == DependencyProperty.UnsetValue || !(bool) v)
+						return Visibility.Collapsed;
 				}
 			}
 
-			return (value) ? Visibility.Visible : Visibility.Collapsed;
+			return Visibility.Visible;
 		}
 
 		public object[] ConvertBack (object value, Type[] targetTypes, object parameter, CultureInfo culture)
diff --git a/Xamarin.PropertyEditing.Windows/NegativeThicknessConverter.cs b/Xamarin.PropertyEditing.Windows/NegativeThicknessConverter.cs
new file mode 100644
index 0000000..a7580ac
--- /dev/null
+++ b/Xamarin.PropertyEditing.Windows/NegativeThicknessConverter.cs
@@ -0,0 +1,31 @@
+using System;
+using System.Globalization;
+using System.Windows;
+using System.Windows.Data;
+
+namespace Xamarin.PropertyEditing.Windows
+{
+	/// <summary>
+	/// Inverts a given thickness
+	/// </summary>
+	internal class NegativeThicknessConverter
+		: IValueConverter
+	{
+		public object Convert (object value, Type targetType, object parameter, CultureInfo culture)
+		{
+			Thickness t;
+			if (value is Thickness thickness) {
+				t = thickness;
+			} else {
+				t = new Thickness (0);
+			}
+
+			return new Thickness (t.Left * -1, t.Top * -1, t.Right * -1, t.Bottom * -1);
+		}
+
+		public object ConvertBack (object value, Type targetType, object parameter, CultureInfo culture)
+		{
+			throw new NotImplementedException ();
+		}
+	}
+}
\ No newline at end of file
diff --git a/Xamarin.PropertyEditing.Windows/PropertyPresenter.cs b/Xamarin.PropertyEditing.Windows/PropertyPresenter.cs
index cb1dc55..ebca5e3 100644
--- a/Xamarin.PropertyEditing.Windows/PropertyPresenter.cs
+++ b/Xamarin.PropertyEditing.Windows/PropertyPresenter.cs
@@ -1,9 +1,16 @@
+using System;
 using System.Collections;
+using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
+using System.Windows.Media;
+using Xamarin.PropertyEditing.ViewModels;
 
 namespace Xamarin.PropertyEditing.Windows
 {
+	[TemplatePart (Name = "addVariant", Type = typeof(ButtonBase))]
+	[TemplatePart (Name = "removeVariant", Type = typeof (ButtonBase))]
 	internal class PropertyPresenter
 		: ContentControl
 	{
@@ -16,6 +23,7 @@ namespace Xamarin.PropertyEditing.Windows
 		{
 			Loaded += OnLoaded;
 			Unloaded += OnUnloaded;
+			DataContextChanged += OnDataContextChanged;
 		}
 
 		public static readonly DependencyProperty LabelProperty = DependencyProperty.Register (
@@ -56,6 +64,95 @@ namespace Xamarin.PropertyEditing.Windows
 			set { SetValue (ShowPropertyButtonProperty, value); }
 		}
 
+		public static readonly DependencyProperty ShowVariantsProperty = DependencyProperty.Register (
+			"ShowVariants", typeof(bool), typeof(PropertyPresenter), new PropertyMetadata (true));
+
+		public bool ShowVariants
+		{
+			get { return (bool) GetValue (ShowVariantsProperty); }
+			set { SetValue (ShowVariantsProperty, value); }
+		}
+
+		public static readonly DependencyProperty LineBrushProperty = DependencyProperty.Register (
+			"LineBrush", typeof (Brush), typeof (PropertyPresenter), new FrameworkPropertyMetadata (Brushes.White, FrameworkPropertyMetadataOptions.AffectsRender));
+
+		public Brush LineBrush
+		{
+			get { return (Brush)GetValue (LineBrushProperty); }
+			set { SetValue (LineBrushProperty, value); }
+		}
+
+		public static readonly DependencyProperty LineThicknessProperty = DependencyProperty.Register (
+			"LineThickness", typeof (double), typeof (PropertyPresenter), new FrameworkPropertyMetadata (1d, FrameworkPropertyMetadataOptions.AffectsRender));
+
+		public static readonly DependencyProperty VariantBackgroundBrushProperty = DependencyProperty.Register (
+			"VariantBackgroundBrush", typeof(Brush), typeof(PropertyPresenter), new FrameworkPropertyMetadata (default(Brush), FrameworkPropertyMetadataOptions.AffectsRender));
+
+		public Brush VariantBackgroundBrush
+		{
+			get { return (Brush) GetValue (VariantBackgroundBrushProperty); }
+			set { SetValue (VariantBackgroundBrushProperty, value); }
+		}
+
+		public double LineThickness
+		{
+			get { return (double)GetValue (LineThicknessProperty); }
+			set { SetValue (LineThicknessProperty, value); }
+		}
+
+		public override void OnApplyTemplate ()
+		{
+			this.addButton = GetTemplateChild ("addVariant") as ButtonBase;
+			this.removeButton = GetTemplateChild ("removeVariant") as ButtonBase;
+			if (this.removeButton != null) {
+				this.removeButton.Click += OnRemoveVariantClicked;
+			}
+
+			this.variationRow = (RowDefinition) GetTemplateChild ("variationRow");
+			this.variationsList = GetTemplateChild ("variationsList") as ItemsControl;
+		}
+
+		protected override void OnRender (DrawingContext drawingContext)
+		{
+			if (this.pvm == null)
+				return;
+
+			base.OnRender (drawingContext);
+			if (!this.pvm.HasVariantChildren && !this.pvm.IsVariant)
+				return;
+
+			drawingContext.DrawRectangle (VariantBackgroundBrush, null, new Rect (0, 0, ActualWidth, ActualHeight));
+
+			var pen = new Pen (LineBrush, LineThickness);
+			double centerLeft = Math.Round (Padding.Left / 2);
+
+			if (this.pvm.HasVariantChildren) {
+				if (this.addButton == null)
+					throw new InvalidOperationException ("addVariant button missing from PropertyPresenter template");
+
+				Point start = this.addButton.TranslatePoint (new Point (this.addButton.ActualWidth / 2, this.addButton.ActualHeight), this);
+				drawingContext.DrawLine (pen, new Point (centerLeft, start.Y), new Point (centerLeft, ActualHeight));
+			} else if (this.pvm.IsVariant) {
+				if (this.removeButton == null)
+					throw new InvalidOperationException ("removeButton button missing from PropertyPresenter template");
+
+				Point start = new Point (centerLeft, 0);
+				Point end = new Point (centerLeft, (this.pvm.GetIsLastVariant ()) ? this.variationRow.ActualHeight / 2 : ActualHeight);
+				drawingContext.DrawLine (pen, start, end);
+				start = new Point (centerLeft, this.variationRow.ActualHeight / 2);
+				end = this.removeButton.TranslatePoint (new Point (0, this.removeButton.ActualHeight / 2), this);
+				drawingContext.DrawLine (pen, start, new Point (end.X, start.Y));
+				start = new Point (end.X + this.removeButton.ActualWidth, start.Y);
+				end = this.variationsList.TranslatePoint (new Point (0, 0), this);
+				drawingContext.DrawLine (pen, start, new Point (end.X, start.Y));
+			}
+		}
+
+		private PropertyViewModel pvm;
+		private ButtonBase addButton, removeButton;
+		private RowDefinition variationRow;
+		private ItemsControl variationsList;
+
 		private void OnLoaded (object sender, RoutedEventArgs e)
 		{
 			IsSubProperty = this.FindParentUnless<PropertyPresenter, PropertyEditorPanel>() != null;
@@ -64,6 +161,54 @@ namespace Xamarin.PropertyEditing.Windows
 		private void OnUnloaded (object sender, RoutedEventArgs e)
 		{
 			IsSubProperty = false;
+			DataContext = null;
+		}
+
+		private void OnDataContextChanged (object sender, DependencyPropertyChangedEventArgs e)
+		{
+			if (this.pvm != null) {
+				this.pvm.CreateVariantRequested -= OnCreateVariantRequested;
+			}
+
+			this.pvm = e.NewValue as PropertyViewModel;
+			if (this.pvm != null && this.pvm.RequestCreateVariantCommand.CanExecute (null)) {
+				this.pvm.CreateVariantRequested += OnCreateVariantRequested;
+			}
+		}
+
+		private void OnCreateVariantRequested (object sender, CreateVariantEventArgs e)
+		{
+			var variation = CreateVariantWindow.RequestVariant (this, this.pvm.Property);
+			if (variation != null)
+				e.Variation = Task.FromResult (variation);
+		}
+
+		private void OnRemoveVariantClicked (object sender, RoutedEventArgs e)
+		{
+			var parent = (FrameworkElement) VisualTreeHelper.GetParent (this);
+			while (!(parent != null && parent.DataContext is PanelGroupViewModel)) {
+				parent = (FrameworkElement) VisualTreeHelper.GetParent (parent);
+			}
+
+			// Ensure we re-draw background and lines if we removed a variant
+			if (parent != null) {
+				bool start = false;
+				int count = VisualTreeHelper.GetChildrenCount (parent);
+				for (int i = 0; i < count; i++) {
+					var element = (FrameworkElement) VisualTreeHelper.GetChild (parent, i);
+					if (element.DataContext == DataContext)
+						continue;
+
+					if (element.DataContext is PropertyViewModel elementVm) {
+						if (Equals (elementVm.Property, this.pvm.Property)) {
+							start = true;
+							element = element.FindChildOrSelf<PropertyPresenter> ();
+							element.InvalidateVisual ();
+						} else if (start)
+							return;
+					}
+				}
+			}
 		}
 	}
 }
\ No newline at end of file
diff --git a/Xamarin.PropertyEditing.Windows/Themes/Resources.xaml b/Xamarin.PropertyEditing.Windows/Themes/Resources.xaml
index cfd9603..e191771 100644
--- a/Xamarin.PropertyEditing.Windows/Themes/Resources.xaml
+++ b/Xamarin.PropertyEditing.Windows/Themes/Resources.xaml
@@ -4,7 +4,9 @@
 					xmlns:drawing="clr-namespace:Xamarin.PropertyEditing.Drawing;assembly=Xamarin.PropertyEditing"
 					xmlns:theme="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero"
 					xmlns:prop="clr-namespace:Xamarin.PropertyEditing.Properties;assembly=Xamarin.PropertyEditing"
-					xmlns:system="clr-namespace:System;assembly=mscorlib">
+					xmlns:system="clr-namespace:System;assembly=mscorlib"
+					xmlns:vm="clr-namespace:Xamarin.PropertyEditing.ViewModels;assembly=Xamarin.PropertyEditing"
+					xmlns:pe="clr-namespace:Xamarin.PropertyEditing;assembly=Xamarin.PropertyEditing">
 
     <ResourceDictionary.MergedDictionaries>
         <ResourceDictionary Source="MenuButtonStyle.xaml" />
@@ -43,6 +45,7 @@
 	<local:BoolsToVisibilityConverter x:Key="BoolsToVisibilityConverter" />
 	<local:CommonBrushToBrushConverter x:Key="BrushConverter" />
 	<local:CommonColorToColorConverter x:Key="ColorConverter" />
+	<local:NegativeThicknessConverter x:Key="NegativeThicknessConverter" />
 	<local:GroupedEditorPropertySelector x:Key="GroupedEditorSelector" />
 
 	<Style TargetType="local:CombinablePredefinedValuesEditor">
@@ -1504,8 +1507,40 @@
 		</Setter>
 	</Style>
 
+	<Style x:Key="VariantButton" TargetType="Button">
+		<Setter Property="Background" Value="Transparent" />
+		<Setter Property="BorderThickness" Value="0" />
+		<Setter Property="FontSize" Value="9" />
+		<Setter Property="Height" Value="10" />
+		<Setter Property="Width" Value="10" />
+		<Setter Property="Foreground" Value="{DynamicResource PropertyButtonBorderBrush}" />
+		<Setter Property="VerticalAlignment" Value="Center" />
+		<Setter Property="SnapsToDevicePixels" Value="True" />
+		<Setter Property="UseLayoutRounding" Value="True" />
+		<Setter Property="Template">
+			<Setter.Value>
+				<ControlTemplate TargetType="Button">
+					<Border Background="{TemplateBinding Background}" BorderThickness="{TemplateBinding BorderThickness}" BorderBrush="{TemplateBinding BorderBrush}">
+						<ContentPresenter />
+					</Border>
+				</ControlTemplate>
+			</Setter.Value>
+		</Setter>
+		<Setter Property="FocusVisualStyle" Value="{DynamicResource GenericVisualFocusStyle}" />
+		<Style.Triggers>
+			<Trigger Property="IsMouseOver" Value="True">
+				<Trigger.Setters>
+					<Setter Property="Background" Value="{DynamicResource ToggleItemMouseOverBackgroundBrush}" />
+				</Trigger.Setters>
+			</Trigger>
+		</Style.Triggers>
+	</Style>
+
 	<Style TargetType="local:PropertyPresenter">
 		<Setter Property="MinHeight" Value="24" />
+		<Setter Property="VariantBackgroundBrush" Value="{DynamicResource PanelGroupSecondaryBackgroundBrush}" />
+		<Setter Property="LineBrush" Value="{DynamicResource VariantLineBrush}" />
+		<Setter Property="SnapsToDevicePixels" Value="True" />
 		<Setter Property="Template">
 			<Setter.Value>
 				<ControlTemplate TargetType="local:PropertyPresenter">
@@ -1518,17 +1553,74 @@
 								<ColumnDefinition Name="propertyButtonColumn" Width="12" />
 							</Grid.ColumnDefinitions>
 							<Grid.RowDefinitions>
+								<RowDefinition Name="variationRow" Height="Auto" />
 								<RowDefinition Height="Auto" MinHeight="24" />
 								<RowDefinition Height="*" />
 								<RowDefinition Height="Auto" />
 							</Grid.RowDefinitions>
 
-							<ToggleButton Name="delveButton" Grid.Column="0" Style="{DynamicResource StandaloneToggleStyle}" Width="11" Height="11" Visibility="{Binding HasItems,ElementName=subProperties,Converter={StaticResource BoolToVisibilityConverter}}" />
-							<TextBlock Name="Label" Margin="0,3,0,3" Grid.Row="0" Grid.Column="1" Text="{TemplateBinding Label}" ToolTip="{Binding Property.Description,Mode=OneTime}" VerticalAlignment="Center" TextWrapping="NoWrap" TextTrimming="CharacterEllipsis" />
-							<ContentPresenter Grid.Row="0" Grid.RowSpan="2" Grid.Column="2" Margin="4,2,0,2" IsEnabled="{Binding Property.CanWrite}" MinHeight="20" />
-							<local:PropertyButton Grid.Row="0" Grid.RowSpan="2" Grid.Column="3" ValueSource="{Binding ValueSource}" IsEnabled="{Binding Property.CanWrite,Mode=OneTime}"/>
+							<Button Name="addVariant" Grid.Column="0" Grid.Row="1" Margin="{TemplateBinding Padding,Converter={StaticResource NegativeThicknessConverter}}" Style="{StaticResource VariantButton}" Command="{Binding RequestCreateVariantCommand,Mode=OneTime}" ToolTip="{x:Static prop:Resources.AddVariant}" AutomationProperties.Name="{x:Static prop:Resources.AddVariant}">
+								<Button.Visibility>
+									<MultiBinding Converter="{StaticResource BoolsToVisibilityConverter}">
+										<Binding Path="HasVariations" Mode="OneTime" />
+										<Binding RelativeSource="{RelativeSource TemplatedParent}" Path="ShowVariants" />
+										<Binding Path="IsEnabled" RelativeSource="{RelativeSource Self}" />
+									</MultiBinding>
+								</Button.Visibility>
+
+								<Grid Width="6" Height="6" VerticalAlignment="Center" HorizontalAlignment="Center">
+									<Line X1="0" X2="6" Y1="3" Y2="3" Stroke="{Binding RelativeSource={RelativeSource AncestorType=Button},Path=Foreground}" StrokeThickness="1" />
+									<Line X1="3" X2="3" Y1="0" Y2="6" Stroke="{Binding RelativeSource={RelativeSource AncestorType=Button},Path=Foreground}" StrokeThickness="1" />
+								</Grid>
+							</Button>
+
+							<Grid Grid.Column="0" Grid.ColumnSpan="4" Grid.Row="0" Visibility="{Binding IsVariant,Mode=OneTime,Converter={StaticResource BoolToVisibilityConverter},FallbackValue=Collapsed}">
+								<Grid.ColumnDefinitions>
+									<ColumnDefinition Width="Auto" />
+									<ColumnDefinition Width="*" />
+								</Grid.ColumnDefinitions>
+
+								<Button Name="removeVariant" Grid.Column="0" Command="{Binding RemoveVariationCommand,Mode=OneTime}" Style="{StaticResource VariantButton}" ToolTip="{x:Static prop:Resources.RemoveVariant}" AutomationProperties.Name="{x:Static prop:Resources.RemoveVariant}">
+									<Grid RenderTransformOrigin="0.5,0.5" Width="6" Height="6" VerticalAlignment="Center" HorizontalAlignment="Center">
+										<Grid.RenderTransform>
+											<RotateTransform Angle="45" />
+										</Grid.RenderTransform>
+
+										<Line X1="0" X2="6" Y1="3" Y2="3" Stroke="{Binding RelativeSource={RelativeSource AncestorType=Button},Path=Foreground}" StrokeThickness="1" />
+										<Line X1="3" X2="3" Y1="0" Y2="6" Stroke="{Binding RelativeSource={RelativeSource AncestorType=Button},Path=Foreground}" StrokeThickness="1" />
+									</Grid>
+								</Button>
+
+								<ItemsControl Margin="5,2,0,2" Name="variationsList" Grid.Column="1" ItemsSource="{Binding Variation,Mode=OneTime}" Focusable="False">
+									<ItemsControl.ItemsPanel>
+										<ItemsPanelTemplate>
+											<VirtualizingStackPanel Orientation="Horizontal" />
+										</ItemsPanelTemplate>
+									</ItemsControl.ItemsPanel>
+									<ItemsControl.ItemTemplate>
+										<DataTemplate DataType="pe:PropertyVariationOption">
+											<Border Background="{DynamicResource VariantBackgroundBrush}" MinHeight="14" Padding="5,0,5,0" Margin="0,0,2,0">
+												<!-- We need to base this font size on some VS setting. !-->
+												<TextBlock Foreground="{DynamicResource VariantForegroundBrush}" FontSize="9px" VerticalAlignment="Center">
+													<TextBlock.Text>
+														<MultiBinding StringFormat="{}{0}: {1}" Mode="OneTime">
+															<Binding Path="Category" Mode="OneTime" />
+															<Binding Path="Name" Mode="OneTime" />
+														</MultiBinding>
+													</TextBlock.Text>
+												</TextBlock>
+											</Border>
+										</DataTemplate>
+									</ItemsControl.ItemTemplate>
+								</ItemsControl>
+							</Grid>
+
+							<ToggleButton Name="delveButton" Grid.Column="0" Grid.Row="0" Style="{DynamicResource StandaloneToggleStyle}" Width="11" Height="11" Visibility="{Binding HasItems,ElementName=subProperties,Converter={StaticResource BoolToVisibilityConverter}}" />
+							<TextBlock Name="Label" Margin="0,3,0,3" Grid.Row="1" Grid.Column="1" Text="{TemplateBinding Label}" ToolTip="{Binding Property.Description,Mode=OneTime}" VerticalAlignment="Center" TextWrapping="NoWrap" TextTrimming="CharacterEllipsis" />
+							<ContentPresenter Grid.Row="1" Grid.RowSpan="2" Grid.Column="2" Margin="4,2,0,2" IsEnabled="{Binding Property.CanWrite}" MinHeight="20" />
+							<local:PropertyButton Grid.Row="1" Grid.RowSpan="2" Grid.Column="3" ValueSource="{Binding ValueSource}" IsEnabled="{Binding Property.CanWrite,Mode=OneTime}"/>
 
-							<ItemsControl Name="subProperties" Background="{DynamicResource PanelGroupSecondaryBackgroundBrush}" Margin="-19,0,0,0" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="4" ItemsSource="{TemplateBinding ItemsSource}" ItemTemplate="{DynamicResource PropertyEditorTemplate}">
+							<ItemsControl Name="subProperties" Background="{DynamicResource PanelGroupSecondaryBackgroundBrush}" Margin="{TemplateBinding Padding,Converter={StaticResource NegativeThicknessConverter}}" Grid.Row="3" Grid.Column="0" Grid.ColumnSpan="4" ItemsSource="{TemplateBinding ItemsSource}" ItemTemplate="{DynamicResource PropertyEditorTemplate}">
 								<ItemsControl.Visibility>
 									<MultiBinding Converter="{StaticResource BoolsToVisibilityConverter}">
 										<Binding ElementName="delveButton" Path="IsChecked" />
diff --git a/Xamarin.PropertyEditing.Windows/Themes/VS.Dark.xaml b/Xamarin.PropertyEditing.Windows/Themes/VS.Dark.xaml
index 880df43..cb76cf1 100644
--- a/Xamarin.PropertyEditing.Windows/Themes/VS.Dark.xaml
+++ b/Xamarin.PropertyEditing.Windows/Themes/VS.Dark.xaml
@@ -16,6 +16,10 @@
 	<SolidColorBrush x:Key="GroupBackgroundBrush">#252526</SolidColorBrush>
 	<SolidColorBrush x:Key="GroupBorderBrush">#434346</SolidColorBrush>
 
+	<SolidColorBrush x:Key="VariantForegroundBrush">#000000</SolidColorBrush>
+	<SolidColorBrush x:Key="VariantBackgroundBrush">#ABABAB</SolidColorBrush>
+	<SolidColorBrush x:Key="VariantLineBrush">#5E5E5E</SolidColorBrush>
+
 	<SolidColorBrush x:Key="AdvancedExpanderCollapsedForegroundBrush">#F1F1F1</SolidColorBrush>
 	<SolidColorBrush x:Key="AdvancedExpanderMouseOverForegroundBrush">#007ACC</SolidColorBrush>
 	<SolidColorBrush x:Key="AdvancedExpanderMouseOverBorderBrush">#3E3E40</SolidColorBrush>
diff --git a/Xamarin.PropertyEditing.Windows/Themes/VS.Light.xaml b/Xamarin.PropertyEditing.Windows/Themes/VS.Light.xaml
index 3e8279a..b881f7f 100644
--- a/Xamarin.PropertyEditing.Windows/Themes/VS.Light.xaml
+++ b/Xamarin.PropertyEditing.Windows/Themes/VS.Light.xaml
@@ -15,6 +15,10 @@
 	<SolidColorBrush x:Key="GroupBackgroundBrush">#FFFFFF</SolidColorBrush>
 	<SolidColorBrush x:Key="GroupBorderBrush">#CCCEDB</SolidColorBrush>
 
+	<SolidColorBrush x:Key="VariantForegroundBrush">#FFFFFF</SolidColorBrush>
+	<SolidColorBrush x:Key="VariantBackgroundBrush">#767676</SolidColorBrush>
+	<SolidColorBrush x:Key="VariantLineBrush">#B7B7B7</SolidColorBrush>
+
 	<SolidColorBrush x:Key="AdvancedExpanderMouseOverForegroundBrush">#007ACC</SolidColorBrush>
 	<SolidColorBrush x:Key="AdvancedExpanderMouseOverBorderBrush">#C9DEF5</SolidColorBrush>
 	<SolidColorBrush x:Key="AdvancedExpanderMouseOverBackgroundBrush">#C9DEF5</SolidColorBrush>
diff --git a/Xamarin.PropertyEditing.Windows/Xamarin.PropertyEditing.Windows.csproj b/Xamarin.PropertyEditing.Windows/Xamarin.PropertyEditing.Windows.csproj
index d3d5f6d..5459fb1 100644
--- a/Xamarin.PropertyEditing.Windows/Xamarin.PropertyEditing.Windows.csproj
+++ b/Xamarin.PropertyEditing.Windows/Xamarin.PropertyEditing.Windows.csproj
@@ -99,6 +99,7 @@
     <Compile Include="IPropertiesHost.cs" />
     <Compile Include="MaterialDesignColorEditorControl.cs" />
     <Compile Include="MultiplyMarginConverter.cs" />
+    <Compile Include="NegativeThicknessConverter.cs" />
     <Compile Include="NullVisibilityConverter.cs" />
     <Compile Include="ObjectEditorControl.cs" />
     <Compile Include="PreviewTemplateSelector.cs" />
diff --git a/Xamarin.PropertyEditing.Windows/XamlHelper.cs b/Xamarin.PropertyEditing.Windows/XamlHelper.cs
index 7f3ac32..7ea99d5 100644
--- a/Xamarin.PropertyEditing.Windows/XamlHelper.cs
+++ b/Xamarin.PropertyEditing.Windows/XamlHelper.cs
@@ -23,6 +23,27 @@ namespace Xamarin.PropertyEditing.Windows
 			}
 		}
 
+		public static T FindChildOrSelf<T> (this UIElement self)
+			where T : UIElement
+		{
+			if (self == null)
+				throw new ArgumentNullException (nameof(self));
+
+			if (self is T t)
+				return t;
+
+			int count = VisualTreeHelper.GetChildrenCount (self);
+			for (int i = 0; i < count; i++) {
+				if (VisualTreeHelper.GetChild (self, i) is UIElement element) {
+					var child = FindChildOrSelf<T> (element);
+					if (child != null)
+						return child;
+				}
+			}
+
+			return null;
+		}
+
 		public static T FindParent<T> (this UIElement self)
 			where T : UIElement
 		{