Question

Question

1. How do you print a FlowDocument that have BlockUIContainer?
2. How can I force a Measure/Update/Arrange on a FlowDocument?

Background

I have a generated FlowDocument with paragraphs of text with a few Rectangle elements filled DrawingBrushes from a resource dictionary and BlockUIContainer with custom controls.

The document renders correctly when viewed in any of the FlowDocument* controls HOWEVER when the document is converted to a FixedDocument/XpsDocument, none of the Rectangle or BlockUIContainer elements render.

I’m almost certain it is because the control has not been measured/arranged, however cannot figure out how to force that to happen before it is converted to the XpsDocument.

• I have walked the LogicalTree recursively and done the following,

  UIElement element = (UIElement)d;
  element.Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity));
  element.Arrange(new Rect(element.DesiredSize));
  element.UpdateLayout();
  

  where d is a DependencyObject. I can see that this sets the ActualWidth and ActualHeight properties when break-pointed in the debugger.

• I have tried forcing the Dispatcher to render as suggested by Will ♦.

Code used to print the XpsDocument

public class XpsDocumentConverter
{

    public static XpsDocumentReference CreateXpsDocument(FlowDocument document)
    {
        // Need to clone the document so that the paginator can work
        FlowDocument clonedDocument = DocumentHelper.Clone<FlowDocument>(document);

        Uri uri = new Uri(String.Format("pack://temp_{0}.xps/", Guid.NewGuid().ToString("N")));
        MemoryStream ms = new MemoryStream();

        Package pkg = Package.Open(ms, FileMode.Create, FileAccess.ReadWrite);
        PackageStore.AddPackage(uri, pkg);
        XpsDocument xpsDocument = new XpsDocument(pkg, CompressionOption.Normal, uri.AbsoluteUri);

        XpsSerializationManager rsm = new XpsSerializationManager(new XpsPackagingPolicy(xpsDocument), false);
        DocumentPaginator paginator = new FixedDocumentPaginator(clonedDocument, A4PageDefinition.Default);
        rsm.SaveAsXaml(paginator);

        return new XpsDocumentReference(ms, xpsDocument);
    }

}

As you can see I’m also using a custom DocumentPaginator named ‘FixedDocumentPaginator’; however I will not post that code as I doubt the issue is there as by the time it starts paginating the document in GetPage(int pageNumber) everything has already been converted a Visual and it is too late for layout.

---

Edit

Hmm. As I typed this, a thought just occurred to me that the cloned document may not have had a Measure/Arrange/UpdateLayout done.

Question: How can I force a Measure/Update/Arrange on a FlowDocument?

A possible hack that I could work would be to show the cloned document in one of the FlowDocumentViewers (perhaps off-screen).

Another possible solution that I just learnt about and haven’t tried would be to call: ContextLayoutManager.From(Dispatcher.CurrentDispatcher).UpdateLayout();

ContextLayoutManager walks the logical tree for you and updates the layout.

Code used for cloning the document

public static FlowDocument Clone(FlowDocument originalDocument)
{
    FlowDocument clonedDocument = new FlowDocument();
    TextRange sourceDocument = new TextRange(originalDocument.ContentStart, originalDocument.ContentEnd);
    TextRange clonedDocumentRange = new TextRange(clonedDocument.ContentStart, clonedDocument.ContentEnd);
    try
    {
        using (MemoryStream ms = new MemoryStream())
        {
            sourceDocument.Save(ms, DataFormats.XamlPackage);
            clonedDocumentRange.Load(ms, DataFormats.XamlPackage);
        }

        clonedDocument.ColumnWidth = originalDocument.ColumnWidth;
        clonedDocument.PageWidth = originalDocument.PageWidth;
        clonedDocument.PageHeight = originalDocument.PageHeight;
        clonedDocument.PagePadding = originalDocument.PagePadding;
        clonedDocument.LineStackingStrategy = clonedDocument.LineStackingStrategy;

        return clonedDocument;
    }
    catch (Exception)
    {               
    }

    return null;
} 

Answer 1

Posting this as future reference for others that are having similar rendering issues with FlowDocument/FixedDocument/XpsDocument.

A few things to note:

• BlockUIContainers are not cloned when you use the above method. This was not immediately obvious until I printed the logical tree out the debug window using some helper methods (these methods are posted below – they are incredibly useful).
• You need to display the document in a viewer and briefly show it on screen. Below is the helper method that I wrote to do this for me.

ForceRenderFlowDocument

private static string ForceRenderFlowDocumentXaml = 
@"<Window xmlns=""http://schemas.microsoft.com/netfx/2007/xaml/presentation""
          xmlns:x=""http://schemas.microsoft.com/winfx/2006/xaml"">
       <FlowDocumentScrollViewer Name=""viewer""/>
  </Window>";

public static void ForceRenderFlowDocument(FlowDocument document)
{
    using (var reader = new XmlTextReader(new StringReader(ForceRenderFlowDocumentXaml)))
    {
        Window window = XamlReader.Load(reader) as Window;
        FlowDocumentScrollViewer viewer = LogicalTreeHelper.FindLogicalNode(window, "viewer") as FlowDocumentScrollViewer;
        viewer.Document = document;
        // Show the window way off-screen
        window.WindowStartupLocation = WindowStartupLocation.Manual;
        window.Top = Int32.MaxValue;
        window.Left = Int32.MaxValue;
        window.ShowInTaskbar = false;
        window.Show();
        // Ensure that dispatcher has done the layout and render passes
        Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Loaded, new Action(() => {}));
        viewer.Document = null;
        window.Close();
    }
}

Edit: I just added window.ShowInTaskbar = false to the method as if you were quick you could see the window appear in the taskbar.

The user will never “see” the window as it is positioned way off-screen at Int32.MaxValue – a trick that was common back in the day with early multimedia authoring (e.g. Macromedia/Adobe Director).

For people searching and finding this question, I can tell you that there is no other way to force the document to render.

Visual and Logical Tree Helpers

public static string WriteVisualTree(DependencyObject parent)
{
    if (parent == null)
        return "No Visual Tree Available. DependencyObject is null.";

    using (var stringWriter = new StringWriter())
    using (var indentedTextWriter = new IndentedTextWriter(stringWriter, "  "))
    {               
        WriteVisualTreeRecursive(indentedTextWriter, parent, 0);
        return stringWriter.ToString();
    }
}

private static void WriteVisualTreeRecursive(IndentedTextWriter writer, DependencyObject parent, int indentLevel)
{
    if (parent == null)
        return;

    int childCount = VisualTreeHelper.GetChildrenCount(parent);
    string typeName = parent.GetType().Name;
    string objName = parent.GetValue(FrameworkElement.NameProperty) as string;

    writer.Indent = indentLevel;
    writer.WriteLine(String.Format("[{0:000}] {1} ({2}) {3}", indentLevel, 
                                                              String.IsNullOrEmpty(objName) ? typeName : objName, 
                                                              typeName, childCount)
                    );

    for (int childIndex = 0; childIndex < childCount; ++childIndex)
        WriteVisualTreeRecursive(writer, VisualTreeHelper.GetChild(parent, childIndex), indentLevel + 1);
}

public static string WriteLogicalTree(DependencyObject parent)
{
    if (parent == null)
        return "No Logical Tree Available. DependencyObject is null.";

    using (var stringWriter = new StringWriter())
    using (var indentedTextWriter = new IndentedTextWriter(stringWriter, "  "))
    {
        WriteLogicalTreeRecursive(indentedTextWriter, parent, 0);
        return stringWriter.ToString();
    }
}

private static void WriteLogicalTreeRecursive(IndentedTextWriter writer, DependencyObject parent, int indentLevel)
{
    if (parent == null)
        return;

    var children = LogicalTreeHelper.GetChildren(parent).OfType<DependencyObject>();
    int childCount = children.Count();

    string typeName = parent.GetType().Name;
    string objName = parent.GetValue(FrameworkElement.NameProperty) as string;

    double actualWidth = (parent.GetValue(FrameworkElement.ActualWidthProperty) as double?).GetValueOrDefault();
    double actualHeight = (parent.GetValue(FrameworkElement.ActualHeightProperty) as double?).GetValueOrDefault();

    writer.Indent = indentLevel;
    writer.WriteLine(String.Format("[{0:000}] {1} ({2}) {3}", indentLevel,
                                                              String.IsNullOrEmpty(objName) ? typeName : objName,
                                                              typeName, 
                                                              childCount)
                    );

    foreach (object child in LogicalTreeHelper.GetChildren(parent))
    {
        if (child is DependencyObject)
            WriteLogicalTreeRecursive(writer, (DependencyObject)child, indentLevel + 1);
    }

}

Usage

#if DEBUG
    Debug.WriteLine("--- Start -------");
    Debug.WriteLine(VisualAndLogicalTreeHelper.WriteLogicalTree(document));
    Debug.WriteLine("--- End -------");
#endif