How to stylise horizontal contextmenu - wpf

Question

I would like to make a contextmenu like the blue one on this image:
I can't figure how to make it so do you have some clues/tutorials/... to share with me?
For now, i'm stuck with this XAML
<Style x:Name="HorizontalContextMenu" TargetType="{x:Type ContextMenu}">
<Setter Property="Background" Value="CadetBlue" />
<Setter Property="BorderBrush" Value="DarkBlue" />
<Setter Property="HorizontalOffset" Value="50"/>
<Setter Property="VerticalOffset" Value="50"/>
<Setter Property="Height" Value="48"/>
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="OverridesDefaultStyle" Value="True" />
<Setter Property="Grid.IsSharedSizeScope" Value="true" />
<Setter Property="HasDropShadow" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ContextMenu">
<Border BorderThickness="0">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="24"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Path Width="100" Height="100"
Data="{DynamicResource RightArrow}"
Fill="Blue" Stretch="Fill"
Grid.Column="0"/>
<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" Grid.Column="1" Orientation="Horizontal"/>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 1

After two days of reflection, i finally achieve this solution:
Frontend XAML
<Button x:Name="btnExpressions" Style="{StaticResource MyMenuButton}" Content="Expressions" Tag="{x:Static iconPacks:PackIconMaterialKind.HeartPulse}" Click="BtnExpressions_Click">
<Button.ContextMenu>
<ContextMenu Style="{StaticResource HorizontalContextMenu}">
<MenuItem Name="BtnA" Header="B" Tag="{x:Static iconPacks:PackIconMaterialKind.RunFast}" Style="{StaticResource HMI}"/>
<MenuItem Name="BtnB" Header="F" Tag="{x:Static iconPacks:PackIconMaterialKind.RunFast}" Style="{StaticResource HMI}"/>
<MenuItem Name="BtnC" Header="T" Tag="{x:Static iconPacks:PackIconMaterialKind.RunFast}" Style="{StaticResource HMI}"/>
</ContextMenu>
</Button.ContextMenu>
</Button>
Style XAML
<Style x:Key="HorizontalContextMenu" TargetType="{x:Type ContextMenu}">
<Setter Property="Background" Value="#AF38789E" />
<Setter Property="BorderThickness" Value="0"/>
<Setter Property="Height" Value="48"/>
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<VirtualizingStackPanel Orientation="Horizontal" Background="Transparent"/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ContextMenu" >
<Border BorderThickness="0">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="10"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Path Data="M0,0.5 L1,0.75 1,0.25Z" Margin="0"
Grid.Column="0"
StrokeThickness="0"
Stroke="{TemplateBinding Background}"
Fill="{TemplateBinding Background}"
Stretch="Fill"
Width="10" Height="20"/>
<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle"Grid.Column="1" Orientation="Horizontal" Background="{TemplateBinding Background}"/>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="HMI" TargetType="MenuItem">
<Setter Property="Foreground" Value="White"/>
<Setter Property="Opacity" Value="0.5"/>
<Setter Property="Width" Value="48" />
<Setter Property="Height" Value="48" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type MenuItem}">
<Border>
<iconPacks:PackIconMaterial Kind="{Binding Tag, RelativeSource={RelativeSource AncestorType=MenuItem}}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Opacity" Value="1" />
</Trigger>
</Style.Triggers>
</Style>
Code behind (VB.NET version)
Private Sub BtnExpressions_Click(sender As Object, e As RoutedEventArgs)
Dim btn As FrameworkElement = sender
If btn IsNot Nothing Then
btn.ContextMenu.PlacementTarget = btn
btn.ContextMenu.Placement = Primitives.PlacementMode.Right
btn.ContextMenu.HorizontalOffset = -10
btn.ContextMenu.VerticalOffset = 0
btn.ContextMenu.IsOpen = True
End If
End Sub
Hope this helps someone else.