sourcegit/src/Resources/Styles/ToggleButton.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style x:Key="Style.ToggleButton.Expender" TargetType="{x:Type ToggleButton}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Grid Background="Transparent" Margin="4,0">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto"/>
                            <ColumnDefinition Width="*"/>
                        </Grid.ColumnDefinitions>

                        <Path
                            x:Name="ExpanderIcon"
                            Grid.Column="0"
                            Width="10" Height="10"
                            Style="{DynamicResource Style.Icon}"
                            Data="{DynamicResource Icon.Down}"
                            Fill="{DynamicResource Brush.FG2}"
                            RenderTransformOrigin=".5,.5">
                            <Path.RenderTransform>
                                <RotateTransform Angle="270"/>
                            </Path.RenderTransform>
                        </Path>
                        
                        <ContentPresenter Grid.Column="1"/>
                    </Grid>

                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter TargetName="ExpanderIcon" Property="RenderTransform">
                                <Setter.Value>
                                    <RotateTransform Angle="0"/>
                                </Setter.Value>
                            </Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    
    <Style x:Key="Style.ToggleButton.Filter" TargetType="{x:Type ToggleButton}">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="BorderThickness" Value="0"/>

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Grid>
                        <Path 
                            x:Name="Icon" 
                            Height="12"
                            Style="{DynamicResource Style.Icon}"
                            Fill="Transparent"
                            Stroke="{DynamicResource Brush.FG2}"
                            StrokeThickness="1"
                            Data="{DynamicResource Icon.Filter}"/>
                    </Grid>

                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter TargetName="Icon" Property="Fill" Value="{DynamicResource Brush.FG2}"/>
                        </Trigger>
                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="IsChecked" Value="False"/>
                                <Condition Property="IsMouseOver" Value="True"/>
                            </MultiTrigger.Conditions>
                            <Setter TargetName="Icon" Property="Fill" Value="{DynamicResource Brush.FG2}"/>
                        </MultiTrigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="Style.ToggleButton.Orientation" TargetType="{x:Type ToggleButton}">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="BorderThickness" Value="0"/>

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Grid Background="Transparent">
                        <Path 
                            x:Name="Icon"
                            Width="18"
                            Height="18"
                            Style="{DynamicResource Style.Icon}"
                            Fill="{DynamicResource Brush.Border1}"
                            Data="{DynamicResource Icon.Horizontal}"/>
                    </Grid>

                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter TargetName="Icon" Property="Data" Value="{DynamicResource Icon.Vertical}"/>
                        </Trigger>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter TargetName="Icon" Property="Fill" Value="{DynamicResource Brush.Accent1}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="Style.ToggleButton.ListOrTree" TargetType="{x:Type ToggleButton}">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="BorderThickness" Value="0"/>

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Grid Background="Transparent">
                        <Path 
                            x:Name="Icon" 
                            Height="12"
                            Width="12"
                            Style="{DynamicResource Style.Icon}"
                            Fill="Transparent"
                            Stroke="{DynamicResource Brush.FG}"
                            StrokeThickness=".4"
                            Data="{DynamicResource Icon.Tree}"/>
                    </Grid>

                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter TargetName="Icon" Property="Data" Value="{DynamicResource Icon.List}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="Style.ToggleButton.SplitDirection" TargetType="{x:Type ToggleButton}">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="BorderThickness" Value="0"/>

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Grid Background="Transparent">
                        <Path 
                            x:Name="Icon" 
                            Height="12"
                            Width="12"
                            Style="{DynamicResource Style.Icon}"
                            Fill="Transparent"
                            Stroke="{DynamicResource Brush.FG}"
                            StrokeThickness=".4"
                            Data="{DynamicResource Icon.SplitVertical}"/>
                    </Grid>

                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter TargetName="Icon" Property="Data" Value="{DynamicResource Icon.SplitHorizontal}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>