WPF TreeViewItem mystery mouseover style - wpf

Question

I'm at my wits end over this, I've spent the better part of the last two days playing with it and googling. When I mouseover my TreeView it works as expected, until you get over the Expander/text at this point a different background and border brush are applied. I've gone silly into trying to eliminate this and nothing at all seems to work. My last overkill attempt below still left me with no idea what is going on.
I assume it's something simple that is just flying over my head, and I know this silly amount of triggers is not required.
As requested, here's a screenshot Issue
And what is desired is the effect that you see where the text is blue and the background is transparent. The background and border brush when over the expander is not wanted
<TreeView x:Name="textureTreeView" ItemsSource="{Binding Category}" Margin="0" SelectedItemChanged="textureTreeView_SelectedItemChanged" Background="#00000000" BorderBrush="{x:Null}" Foreground="#00000000" IsTextSearchEnabled="True">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type local1:CategoryViewModel}" ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}" IsHitTestVisible="False"/> <!-- This eliminated the text from causing the issue -->
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.Resources>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Foreground" Value="#FFA1A1A1"/>
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
<Setter Property="FontWeight" Value="Normal"/>
<Style.Triggers>
<Trigger Property="IsFocused" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="Foreground" Value="#FFFFFFFF"/>
</Trigger>
<Trigger Property="Expander.IsMouseOver" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="Grid.IsMouseOver" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="StackPanel.IsMouseOver" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="TextBlock.IsMouseOver" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="ItemsPresenter.IsMouseOver" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="Path.IsMouseOver" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="ToggleButton.IsMouseOver" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="ToggleButton.IsChecked" Value="true">
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="ToggleButton.IsMouseOver" Value="true"/>
<Condition Property="ToggleButton.IsChecked" Value="true"/>
</MultiTrigger.Conditions>
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="ToggleButton.IsMouseOver" Value="true"/>
<Condition Property="ToggleButton.IsChecked" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</MultiTrigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
Update: Thanks to #Gui's suggestion I've managed to drill down farther into exactly what is happening. There is an unnamed Border that is pulling template properties that is applying the style.
I've already tried removing all my style templates, I have no idea where this is being pulled from, and while I'm now working on it, I'm having a very difficult time addressing the border itself to set a different style.
Update: For the life of me I can't get this border to take a styling, it doesn't seem to be part of any of the control templates I've downloaded.

Answer 1

I got it working!
I tried like a million things, and no templates or setters would stick. Finally I put the control template directly into the treeviewitem's style with an override setter, and it worked. I'm having one small issue with getting the expander fill colour to set on the treeviewitem's mouseover, but this isn't a huge issue for me.
In Resources:
<SolidColorBrush x:Key="GlyphBrush" Color="#FFA1A1A1" />
<Style x:Key="ExpandCollapseToggleStyle" TargetType="ToggleButton">
<Setter Property="Foreground" Value="#FFFFFF"/>
<Setter Property="Focusable" Value="False"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ToggleButton">
<Grid Width="15" Height="13" Background="Transparent">
<Path x:Name="ExpandPath" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="1,1,1,1" Fill="{StaticResource GlyphBrush}" Data="M 4 0 L 8 4 L 4 8 Z"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="True">
<Setter Property="Data" TargetName="ExpandPath" Value="M 0 4 L 8 4 L 4 8 Z"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="TreeViewItemFocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Border>
<Rectangle Margin="0,0,0,0" StrokeThickness="5" Stroke="#FF717171" StrokeDashArray="1 2" Opacity="0"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Then in the page:
<TreeView x:Name="textureTreeView" ItemsSource="{Binding Category}" SelectedItemChanged="textureTreeView_SelectedItemChanged" Background="#00000000" BorderBrush="{x:Null}" Foreground="#00000000" IsTextSearchEnabled="True">
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type local1:CategoryViewModel}" ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}" IsHitTestVisible="False"/>
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.Resources>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="HorizontalContentAlignment" Value="{Binding Path=HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding Path=VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="Padding" Value="1,0,0,0"/>
<Setter Property="Foreground" Value="#FFA1A1A1"/>
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
<Setter Property="FontWeight" Value="Normal"/>
<Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisual}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="19" Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition/>
</Grid.RowDefinitions>
<ToggleButton x:Name="Expander" Style="{StaticResource ExpandCollapseToggleStyle}" IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press"/>
<Border Name="Bd" Grid.Column="1" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
<ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"/>
</Border>
<ItemsPresenter x:Name="ItemsHost" Grid.Row="1" Grid.Column="1" Grid.ColumnSpan="2"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsFocused" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="Foreground" Value="#FFFFFFFF"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Border.Background" Value="#00000000"/>
<Setter Property="Background" Value="#00000000"/>
<Setter Property="BorderBrush" Value="#00000000"/>
<Setter Property="Foreground" Value="#FF58A6C3"/>
</Trigger>
<Trigger Property="IsExpanded" Value="false">
<Setter TargetName="ItemsHost" Property="Visibility" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter TargetName="Expander" Property="Visibility" Value="Hidden"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasHeader" Value="false"/>
<Condition Property="Width" Value="Auto"/>
</MultiTrigger.Conditions>
<Setter TargetName="PART_Header" Property="MinWidth" Value="75"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasHeader" Value="false"/>
<Condition Property="Height" Value="Auto"/>
</MultiTrigger.Conditions>
<Setter TargetName="PART_Header" Property="MinHeight" Value="19"/>
</MultiTrigger>
<Trigger Property="IsSelected" Value="true">
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="Foreground" Value="#ffffffff"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="true"/>
<Condition Property="IsSelectionActive" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>