SnapList.xaml

<UserControl x:Class="ATypeSurfaceControls.SnapList"
             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:s="http://schemas.microsoft.com/surface/2008"
             xmlns:local="clr-namespace:ATypeSurfaceControls"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300">
    <UserControl.Resources>
        <local:EndToMarginConverter x:Key="ETMc"/>
        <local:VerticalHalfMarginConverter x:Key="Vc"/>
    </UserControl.Resources>

    <Grid x:Name="LayoutRoot">
        <s:SurfaceListBox x:Name="List" VerticalAlignment="Center" HorizontalAlignment="Stretch"
                            ItemsSource="{Binding ItemsSource, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:SnapList}}}"
                            ScrollViewer.HorizontalScrollBarVisibility="Disabled">
            <s:SurfaceListBox.Style>
                <Style TargetType="{x:Type s:SurfaceListBox}">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type s:SurfaceListBox}">
                                <s:SurfaceScrollViewer HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Hidden" >
                                    <VirtualizingStackPanel Orientation="Vertical" IsItemsHost="True"
                                                            Margin="{Binding ActualHeight, ElementName=LayoutRoot, Converter={StaticResource Vc}}"></VirtualizingStackPanel>
                                </s:SurfaceScrollViewer>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </s:SurfaceListBox.Style>
            <s:SurfaceListBox.ItemContainerStyle>
                <Style TargetType="{x:Type s:SurfaceListBoxItem}">
                    <Setter Property="RenderTransformOrigin">
                        <Setter.Value>
                            <Point X="0.5" Y="0.5"/>
                        </Setter.Value>
                    </Setter>
                    <Setter Property="Height" Value="200"/>
                    <Setter Property="Padding" Value="0"/>
                    <Setter Property="VerticalContentAlignment" Value="Center"/>
                    <Setter Property="Margin" Value="4"/>
                    <Setter Property="ContentTemplate" Value="{Binding ItemContentTemplate, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:SnapList}}}">
                    </Setter>
                    <Setter Property="Template" Value="{Binding ItemTemplate, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:SnapList}}}">
                    </Setter>
                    <EventSetter Event="Selected" Handler="ListItem_Selected"/>
                </Style>
            </s:SurfaceListBox.ItemContainerStyle>
        </s:SurfaceListBox>
        <local:ScrollViewerOffsetMediator x:Name="Mediator" />
    </Grid>
</UserControl>