WPF DocumentViewer enable scroll on touch screen for XPS document - wpf

Question

When showing an XPS document in the DocumentViewer control of a WPF application it does not allow you to scroll its content on a touch enabled tablet just my moving your fingers over the screen.
Instead it selects the text. The only way of scrolling on a touch enabled device is by using the vertical scrollbar.
Is there a way to enable touch scrolling by moving your fingers on the content itself instead of on the vertical scrollbar?
By overriding some styles I could prevent the text selection but it still does not allow me to scroll. ( https://stackoverflow.com/a/415155/187650 )

Answer 1

I had the same problem and i made a solution and it works perfectly.
I made an own Xps Document class to set URI dynamically:
public class ManualXpsDocument : XpsDocument
{
private const string _uriOfDoc= "...\\path.xps";
public ManualXpsDocument(FileAccess fileAccess) : base(_uriOfDoc, fileAccess)
{
}
}
Here is the xaml part of window (or control):
<Grid.Resources>
<ObjectDataProvider x:Key="myDataSource" MethodName="GetFixedDocumentSequence"
ObjectType="{x:Type manual:ManualXpsDocument}">
<ObjectDataProvider.ConstructorParameters>
<io:FileAccess>Read</io:FileAccess>
</ObjectDataProvider.ConstructorParameters>
</ObjectDataProvider>
</Grid.Resources>
<DocumentViewer x:Name="Viewer" Document="{Binding Source={StaticResource myDataSource}}">
<DocumentViewer.Resources>
<Style TargetType="ToolBar">
<Setter Property="Visibility" Value="Collapsed" />
</Style>
<Style TargetType="{x:Type ContentControl}">
<Setter Property="Visibility" Value="Collapsed" />
</Style>
</DocumentViewer.Resources>
<DocumentViewer.Style>
<Style TargetType="{x:Type DocumentViewer}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DocumentViewer}">
<controls:CustomScrollViewer x:Name="PART_ContentHost">
<controls:CustomScrollViewer.Style>
<Style TargetType="{x:Type ScrollViewer}">
<Setter Property="Focusable" Value="false" />
<Setter Property="IsDeferredScrollingEnabled" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ScrollViewer}">
<Border BorderBrush="#00000000"
BorderThickness="0,2,0,0">
<Grid Background="{TemplateBinding Background}"
SnapsToDevicePixels="true">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<ScrollContentPresenter Name="PART_ScrollContentPresenter"
ScrollViewer.IsDeferredScrollingEnabled="True"
KeyboardNavigation.DirectionalNavigation="Local"
CanContentScroll="True"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
<controls:CustomScrollBar Name="PART_VerticalScrollBar"
Style="{DynamicResource ScrollBar}"
Grid.Column="1"
Value="{TemplateBinding VerticalOffset}"
Maximum="{TemplateBinding ScrollableHeight}"
ViewportSize="{TemplateBinding ViewportHeight}"
Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}" />
<controls:CustomScrollBar Name="PART_HorizontalScrollBar"
Grid.Row="1"
Grid.ColumnSpan="2"
Style="{DynamicResource ScrollBar}"
Orientation="Horizontal"
Value="{TemplateBinding HorizontalOffset}"
Maximum="{TemplateBinding ScrollableWidth}"
ViewportSize="{TemplateBinding ViewportWidth}"
Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}" />
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</controls:CustomScrollViewer.Style>
</controls:CustomScrollViewer>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</DocumentViewer.Style>
</DocumentViewer>
Here is The xaml.cs part of Window (or control):
public ctor()
{
InitializeComponent();
PreviewTouchMove += ScrollingHandler;
}
private void ScrollingHandler(object sender, TouchEventArgs e)
{
TouchPoint tp = e.GetTouchPoint(Viewer);
if (tp.Action == TouchAction.Move)
{
//_scrollingInt is not necessary but Move procedure of Viewer has const value to scroll and the optimalization is recommended.
if (_lastYPosition > tp.Position.Y + _scrollingInt)
{
Viewer.MoveDown();
_lastYPosition = tp.Position.Y;
}
else if (_lastYPosition < tp.Position.Y - _scrollingInt)
{
Viewer.MoveUp();
_lastYPosition = tp.Position.Y;
}
}
// Viewer.IsHitTestVisible = false; this setting can disable the selection too,but if you use this, the hyperlinks won't work too.
Viewer.GetType().GetProperty("IsSelectionEnabled", BindingFlags.Instance | BindingFlags.NonPublic).SetValue(Viewer, false, null);
//set false "IsSelectionEnabled" "hidden" property instead of Viewer.IsHitTestVisible = false, because the hyperlinks will work too.
e.Handled = true;
}
ScrollingHandler method solve the problem. This procedure do the scrolling of document viewer and disable the selection but the hyperlink function still available.