Change parent properties through trigger - wpf

Question

I have the following XAML for a ComboBox custom design
<ControlTemplate TargetType="{x:Type ToggleButton}" x:Key="ComboBoxToggleButtonTemplate">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="32" />
</Grid.ColumnDefinitions>
<Border BorderBrush="{StaticResource CleoComboBoxBorderBrush}" BorderThickness="1,1,1,1" x:Name="Border" Background="{StaticResource CleoComboBoxBackgroundBrush}" Grid.ColumnSpan="2" />
<Border x:Name="Border2" Margin="1,1,1,1" BorderBrush="{StaticResource CleoComboBoxBorderBrush}" BorderThickness="0,0,0,0" Background="{StaticResource CleoComboBoxBackgroundBrush}" Grid.Column="0" />
<Path Margin="0,0,3,0" Data="M0,0 L4,4 8,0z" HorizontalAlignment="Center" Fill="{StaticResource CleoComboBoxToggleButtonBrush}" x:Name="Arrow" VerticalAlignment="Center" Width="8" Grid.Column="1" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsFocused" Value="True">
<Setter Property="BorderBrush" TargetName="Border" Value="{StaticResource CleoComboBoxBorderSelectedBrush}" />
<Setter Property="BorderThickness" TargetName="Border" Value="2" />
<Setter Property="Shape.Fill" TargetName="Arrow" Value="{StaticResource CleoComboBoxBorderSelectedBrush}" />
</Trigger>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="BorderBrush" TargetName="Border" Value="{StaticResource CleoComboBoxBorderHoverBrush}" />
<Setter Property="BorderThickness" TargetName="Border" Value="2" />
<Setter Property="BorderBrush" TargetName="Border2" Value="{StaticResource CleoComboBoxBorderHoverBrush}" />
<Setter Property="BorderThickness" TargetName="Border2" Value="1,1,0,1" />
<Setter Property="Shape.Fill" TargetName="Arrow" Value="{StaticResource CleoComboBoxBorderHoverBrush}" />
</Trigger>
<Trigger Property="IsChecked" Value="True">
<Setter Property="BorderBrush" TargetName="Border" Value="{StaticResource CleoComboBoxBorderSelectedBrush}" />
<Setter Property="BorderThickness" TargetName="Border" Value="2" />
<Setter Property="BorderBrush" TargetName="Border2" Value="{StaticResource CleoComboBoxBorderSelectedBrush}" />
<Setter Property="BorderThickness" TargetName="Border2" Value="1,1,0,1" />
<Setter Property="Shape.Fill" TargetName="Arrow" Value="{StaticResource CleoComboBoxBorderSelectedBrush}" />
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Background" TargetName="Border" Value="#FFEEEEEE" />
<Setter Property="BorderBrush" TargetName="Border" Value="#FFAAAAAA" />
<Setter Property="Background" TargetName="Border2" Value="#FFEEEEEE" />
<Setter Property="BorderBrush" TargetName="Border2" Value="#FFAAAAAA" />
<Setter Property="Foreground" Value="#FF888888" />
<Setter Property="Shape.Fill" TargetName="Arrow" Value="#66ADADAD" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
<ControlTemplate TargetType="{x:Type TextBox}" x:Key="ComboBoxTextBoxTemplate">
<Border x:Name="PART_ContentHost" Background="{StaticResource CleoComboBoxBackgroundBrush}" Focusable="False" />
</ControlTemplate>
<Style TargetType="{x:Type ComboBoxItem}">
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
<Setter Property="Foreground" Value="{StaticResource CleoComboBoxTextBrush}" />
<Setter Property="OverridesDefaultStyle" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ComboBoxItem}">
<Border x:Name="Border" SnapsToDevicePixels="True" Padding="4,4,4,4" BorderBrush="Transparent" BorderThickness="1,1,1,1">
<ContentControl ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" />
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsHighlighted" Value="True">
<Setter Property="Background" TargetName="Border" Value="{StaticResource CleoComboBoxHighlightedItemBackgroundBrush}"/>
<Setter Property="BorderBrush" TargetName="Border" Value="{StaticResource CleoComboBoxHighlightedItemBorderBrush}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Foreground" Value="#FF888888"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style TargetType="{x:Type ComboBox}">
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="OverridesDefaultStyle" Value="True" />
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
<Setter Property="ScrollViewer.CanContentScroll" Value="True" />
<Setter Property="TextElement.Foreground" Value="{StaticResource CleoComboBoxTextBrush}" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ComboBox}">
<Grid x:Name="Grid">
<ToggleButton ClickMode="Press" x:Name="ToggleButton" IsChecked="{Binding Path=IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"
Focusable="False" Grid.Column="2" Template="{StaticResource ComboBoxToggleButtonTemplate}" />
<ContentPresenter Margin="3,3,23,3" HorizontalAlignment="Left" x:Name="ContentSite" VerticalAlignment="Center"
ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" Content="{TemplateBinding SelectionBoxItem}" IsHitTestVisible="False" />
<TextBox Margin="3,3,23,3" Visibility="Hidden" HorizontalAlignment="Left" x:Name="PART_EditableTextBox" Background="Transparent"
VerticalAlignment="Center" Style="{x:Null}" IsReadOnly="False" Focusable="True" xml:space="preserve" Template="{StaticResource ComboBoxTextBoxTemplate}" />
<Popup Placement="Bottom" x:Name="Popup" Focusable="False" AllowsTransparency="True" IsOpen="{TemplateBinding IsDropDownOpen}" PopupAnimation="Fade">
<Grid MinWidth="{TemplateBinding ActualWidth}" MaxHeight="{TemplateBinding ComboBox.MaxDropDownHeight}" x:Name="DropDown" SnapsToDevicePixels="True">
<Border BorderBrush="{StaticResource CleoComboBoxBorderBrush}" BorderThickness="1,1,1,1" x:Name="DropDownBorder" Background="{StaticResource CleoComboBoxBackgroundBrush}" />
<ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
<ItemsPresenter KeyboardNavigation.DirectionalNavigation="Contained" />
</ScrollViewer>
</Grid>
</Popup>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="HasItems" Value="False">
<Setter Property="MinHeight" TargetName="DropDownBorder" Value="95" />
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Foreground" Value="#FF888888" />
</Trigger>
<Trigger Property="IsGrouping" Value="True">
<Setter Property="ScrollViewer.CanContentScroll" Value="False" />
</Trigger>
<Trigger Property="Window.AllowsTransparency" SourceName="Popup" Value="True">
<Setter Property="Margin" TargetName="DropDownBorder" Value="0,2,0,0" />
</Trigger>
<Trigger Property="IsEditable" Value="True">
<Setter Property="KeyboardNavigation.IsTabStop" Value="False" />
<Setter Property="Visibility" TargetName="PART_EditableTextBox" Value="Visible" />
<Setter Property="Visibility" TargetName="ContentSite" Value="Hidden" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
In the ComboBoxToggleButtonTemplate I have added a Trigger for the IsFocussed property where the value is true and want to change the border color and thickness (amongst other things)
I have tried this trigger in the ComboBox style as well but I cannot seem to get this to work at all, and really hitting a brick wall as to what the issue may be, can anyone shed any light on this please?

Answer 1

A combo box toggle button never gets the focus, so using that as a trigger wouldn't work. The focus always stays with the edit / static text or the item list in the drop down.

Answer 2

The Condition has to look something like this
<Condition Binding="{Binding IsFocussed, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type ComboBox}}}" Value="true"/>
when templating from within the Toggle Button.