Multi-touch ScrollViewer eating touch events - wpf

Question

WPF 4.0:
I have scroll viewer with many Sliders inside of it. I want the scroll viewer to pan with touch, and I want the internal slider to also respond to touch.
Unfortunately, the scroll viewer is eating the "TouchMove" events and not passing them down to the slider control. Any idea how to fix this?
Here is my XAML:
<Window x:Class="ScrollingTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ItemsControl ItemsSource="{Binding}">
<ItemsControl.Template>
<ControlTemplate>
<ScrollViewer VerticalScrollBarVisibility="Auto" PanningMode="Both" >
<ItemsPresenter />
</ScrollViewer>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Height="100" BorderThickness="2" BorderBrush="Black">
<Slider Value="{Binding ., Mode=TwoWay}" Width="300" Minimum="0" Maximum="100" />
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</Window>
And my Code-behind:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = Items;
}
public IEnumerable<int> Items
{
get
{
return Enumerable.Range(0, 50);
}
}
}

Answer 1

Please see my answer to this question: ScrollViewer in a touch interface not working properly
I just resolved this issue in our app as well using a custom Thumb control - in my answer I explain what is causing the problem.

Answer 2

This sounds like a case of "routed event marked as handled". Can you try using AddHandler to subscribe to that event, and set the last parameter "handledEventsToo" to true?
Cheers,
Laurent

Answer 3

It's handling the TouchMove event, most likely. There are bubbling events (PreviewTouchMove, etc) you could handle in your Slider control. You would need to coordinate how you want the touch events to be handled.

Answer 4

You can try to make your custom class, derived from ScrollViewer and override OnTouchMove method.
public class CustomScrollViewer : System.Windows.Controls.ScrollViewer
{
protected override void OnTouchMove(System.Windows.Input.TouchEventArgs e)
{
// delete the base.OnTouchMove() call to prevent event being "eat" :)
}
}
Then, you edit the xaml like this:
<Window x:Class="ScrollingTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ItemsControl ItemsSource="{Binding}">
<ItemsControl.Template>
<ControlTemplate>
<local:CustomScrollViewer VerticalScrollBarVisibility="Auto" PanningMode="Both" >
<ItemsPresenter />
</local:CustomScrollViewer>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Height="100" BorderThickness="2" BorderBrush="Black">
<Slider Value="{Binding ., Mode=TwoWay}" Width="300" Minimum="0" Maximum="100" />
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</Window>