NumericSpinner.xaml

<UserControl x:Class="Stopbyte.Controls.NumericSpinner"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:Stopbyte.Controls"
             mc:Ignorable="d" x:Name="root_numeric_spinner"
             d:DesignHeight="32" d:DesignWidth="100">
    <UserControl.Resources>
        <ControlTemplate x:Key="updown_button_style" TargetType="Button">
            <Border x:Name="br" BorderThickness="0" BorderBrush="{DynamicResource ThemeBrushDark}" 
                            Background="{DynamicResource ThemeBrush}" CornerRadius="0">
                <ContentPresenter x:Name="cp" TextElement.Foreground="{TemplateBinding Foreground}" 
                                          HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" 
                                          VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
            </Border>
            <ControlTemplate.Triggers>
                <Trigger Property="IsMouseOver" Value="true">
                    <Setter TargetName="br" Property="Background" Value="{DynamicResource ThemeBrushActive}" />
                </Trigger>
                <Trigger Property="IsEnabled" Value="false">
                    <Setter TargetName="br" Property="Background" Value="Silver" />
                </Trigger>
            </ControlTemplate.Triggers>
        </ControlTemplate>

        <Style TargetType="Button">
            <Setter Property="Template" Value="{StaticResource updown_button_style}" />
        </Style>
    </UserControl.Resources>
    <Border>
        <Border.OpacityMask>
            <VisualBrush>
                <VisualBrush.Visual>
                    <Border Background="Black" SnapsToDevicePixels="True"
                            CornerRadius="4"
                            Width="{Binding ActualWidth, RelativeSource={RelativeSource FindAncestor, AncestorType=Border}}"
                            Height="{Binding ActualHeight, RelativeSource={RelativeSource FindAncestor, AncestorType=Border}}" />
                </VisualBrush.Visual>
            </VisualBrush>
        </Border.OpacityMask>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition />
                <RowDefinition />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition />
                <ColumnDefinition Width="22" />
            </Grid.ColumnDefinitions>
            <TextBox x:Name="tb_main" x:FieldModifier="private" FontWeight="Medium" FontSize="14" VerticalContentAlignment="Center" Padding="5,1" 
                     Grid.Column="0" Grid.RowSpan="2" Text="0" />
            <Button x:Name="cmdUp" x:FieldModifier="private" Grid.Column="1" Grid.Row="0" Width="auto" Height="auto" Click="cmdUp_Click">
                <Button.Content>
                    <Path HorizontalAlignment="Center" VerticalAlignment="Center" Fill="Black" Data="M4,0 L0,4 L8,4 z"/>
                </Button.Content>
            </Button>
            <Button x:Name="cmdDown" x:FieldModifier="private" Grid.Column="1" Grid.Row="1" Width="auto" Height="auto" Click="cmdDown_Click">
                <Button.Content>
                    <Path HorizontalAlignment="Center" VerticalAlignment="Center" Fill="Black" Data="M0,0 L8,0 L4,4 z"/>
                </Button.Content>
            </Button>
            <Border BorderBrush="Gray" IsHitTestVisible="False" BorderThickness="1" CornerRadius="4" Grid.RowSpan="2" 
                    Grid.ColumnSpan="2" Padding="0" Margin="0" />
        </Grid>
    </Border>
</UserControl>