How to enable horizontal scrolling with mouse?

Question

I cannot determine how to scroll horizontally using the mouse wheel. Vertical scrolling works well automatically, but I need to scroll my content horizontally. My code looks like this:

<ListBox x:Name="receiptList"
         Margin="5,0"
         Grid.Row="1"
         ItemTemplate="{StaticResource receiptListItemDataTemplate}"
         ItemsSource="{Binding OpenReceipts}"
         ScrollViewer.VerticalScrollBarVisibility="Disabled">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel Orientation="Horizontal"
                        ScrollViewer.HorizontalScrollBarVisibility="Visible"/>
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
</ListBox>

My item template looks like this:

<DataTemplate x:Key="receiptListItemDataTemplate">
    <RadioButton GroupName="Numbers"
                 Command="{Binding Path=DataContext.SelectReceiptCommand,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type POS:PointOfSaleControl}}}"
                 CommandParameter="{Binding }"
                 Margin="2,0"
                 IsChecked="{Binding IsSelected}">
        <RadioButton.Template>
            <ControlTemplate TargetType="{x:Type RadioButton}" >
                <Grid x:Name="receiptGrid" >
                    <Grid>
                        <Border BorderThickness="2" 
                                BorderBrush="Green" 
                                Height="20" 
                                Width="20">
                            <Grid x:Name="radioButtonGrid" 
                                  Background="DarkOrange">
                                <TextBlock x:Name="receiptLabel"
                                           HorizontalAlignment="Center"
                                           VerticalAlignment="Center"
                                           Text="{Binding Path=NumberInQueue, Mode=OneWay}"
                                           FontWeight="Bold"
                                           FontSize="12"
                                           Foreground="White">
                                </TextBlock>
                            </Grid>
                        </Border>
                    </Grid>
                </Grid>

                <ControlTemplate.Triggers>
                    <Trigger Property="IsChecked" Value="True">
                        <Setter Property="Margin" 
                                TargetName="receiptGrid" 
                                Value="2,2,-1,-1"/>
                        <Setter Property="Background"
                                TargetName="radioButtonGrid" 
                                Value="Maroon"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </RadioButton.Template>
    </RadioButton>          
</DataTemplate>

Is there another method or control that I need to add to get that functionality?

Answer 1

Here's a complete behaviour. Add the below class to your code, then in your XAML set the attached property to true on any UIElement that contains a ScrollViewer as a visual child.

<MyVisual ScrollViewerHelper.ShiftWheelScrollsHorizontally="True" />

The class:

public static class ScrollViewerHelper
{
    public static readonly DependencyProperty ShiftWheelScrollsHorizontallyProperty
        = DependencyProperty.RegisterAttached("ShiftWheelScrollsHorizontally",
            typeof(bool),
            typeof(ScrollViewerHelper),
            new PropertyMetadata(false, UseHorizontalScrollingChangedCallback));

    private static void UseHorizontalScrollingChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var element = d as UIElement;

        if (element == null)
            throw new Exception("Attached property must be used with UIElement.");

        if ((bool)e.NewValue)
            element.PreviewMouseWheel += OnPreviewMouseWheel;
        else
            element.PreviewMouseWheel -= OnPreviewMouseWheel;
    }

    private static void OnPreviewMouseWheel(object sender, MouseWheelEventArgs args)
    {
        var scrollViewer = ((UIElement)sender).FindDescendant<ScrollViewer>();

        if (scrollViewer == null)
            return;

        if (Keyboard.Modifiers != ModifierKeys.Shift)
            return;

        if (args.Delta < 0)
            scrollViewer.LineRight();
        else
            scrollViewer.LineLeft();

        args.Handled = true;
    }

    public static void SetShiftWheelScrollsHorizontally(UIElement element, bool value) => element.SetValue(ShiftWheelScrollsHorizontallyProperty, value);
    public static bool GetShiftWheelScrollsHorizontally(UIElement element) => (bool)element.GetValue(ShiftWheelScrollsHorizontallyProperty);

    [CanBeNull]
    private static T FindDescendant<T>([CanBeNull] this DependencyObject d) where T : DependencyObject
    {
        if (d == null)
            return null;

        var childCount = VisualTreeHelper.GetChildrenCount(d);

        for (var i = 0; i < childCount; i++)
        {
            var child = VisualTreeHelper.GetChild(d, i);

            var result = child as T ?? FindDescendant<T>(child);

            if (result != null)
                return result;
        }

        return null;
    }
}

This answer fixes a few bugs in Johannes' answer, such as not filtering by Shift key, scrolling both horizontally and vertically at the same time (motion was diagonal) and the inability to disable the behaviour by setting the property to false.

Answer 2

I wrote an Attached Property for this purpose to reuse it on every ItemsControl containing an ScrollViewer. FindChildByType is an Telerik extension but can also be found here.

 public static readonly DependencyProperty UseHorizontalScrollingProperty = DependencyProperty.RegisterAttached(
            "UseHorizontalScrolling", typeof(bool), typeof(ScrollViewerHelper), new PropertyMetadata(default(bool), UseHorizontalScrollingChangedCallback));

        private static void UseHorizontalScrollingChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
        {
            ItemsControl itemsControl = dependencyObject as ItemsControl;

            if (itemsControl == null) throw new ArgumentException("Element is not an ItemsControl");

            itemsControl.PreviewMouseWheel += delegate(object sender, MouseWheelEventArgs args)
            {
                ScrollViewer scrollViewer = itemsControl.FindChildByType<ScrollViewer>();

                if (scrollViewer == null) return;

                if (args.Delta < 0)
                {
                    scrollViewer.LineRight();
                }
                else
                {
                    scrollViewer.LineLeft();
                }
            };
        }


        public static void SetUseHorizontalScrolling(ItemsControl element, bool value)
        {
            element.SetValue(UseHorizontalScrollingProperty, value);
        }

        public static bool GetUseHorizontalScrolling(ItemsControl element)
        {
            return (bool)element.GetValue(UseHorizontalScrollingProperty);
        }