XPS export off-screen RenderSurface

Hi SciChart,

We are experiencing a SciChart XPS export issue.

I am using a FlowDocumentPageViewer with a FlowDocument containing SciChart graphs. My goal is to export all pages of the FlowDocument to an XPS file using the XamlRenderSurface to save in vector graphics. However, I’m facing an issue where only the currently selected page exports correctly, while the other pages display empty graphs.

By default, we employ the VisualXcceleratorRenderSurface for all SciChart render surfaces. Before exporting, I programmatically switch them to XamlRenderSurface to save in vector graphics. This approach works well when all the graphs have been rendered on-screen at least once with the new surface type before exporting. However, if a graph hasn’t been rendered on-screen before exporting, it appears empty, and only the graphs from the selected page export correctly. You can find code snippets below.

XAML code:

<s:SciChartSurface
    x:Name="PART_Surface"
    ...
    RenderSurface="{TemplateBinding RenderType, Converter={StaticResource RenderTypeConverter}}"
    ...

Converter:

public class RenderTypeConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        // Set render settings
        return (RenderType)value switch
        {
            RenderType.DirectX => new VisualXcceleratorRenderSurface(),
            RenderType.HighQuality => new HighQualityRenderSurface(),
            RenderType.HighSpeed => new HighSpeedRenderSurface(),
            RenderType.Vector => new XamlRenderSurface(),
            _ => new HighSpeedRenderSurface(),
        };
    }
    ...
}

Export:

private void ExportVector(string fullPath)
{
    // Sets the RenderType to Vector for all surfaces
    // This invokes RenderTypeConverter to set the RenderSurface to XamlRenderSurface
    // Since they are bound in the XAML code
    SetAxesSurfacesRenderToVector();

    XPS_Export_AllPagesOfFlowDocument(fullPath);

    // DirectX is always the default for all surfaces that we use
    ResetAxesSurfacesToDirectX();
}
private void XPS_Export_AllPagesOfFlowDocument(string fullPath)
{
    using (var package = Package.Open(fullPath, FileMode.Create))
    {
        using (var xpsDocument = new XpsDocument(package, CompressionOption.Maximum))
        {
            var xpsSerializationManager = new XpsSerializationManager(new XpsPackagingPolicy(xpsDocument), false);
            var documentPaginator = ((IDocumentPaginatorSource)FlowDocument)?.DocumentPaginator;
            xpsSerializationManager.SaveAsXaml(documentPaginator);

            xpsDocument.Close();
        }
    }
}

The binding and the converter works for all offscreen elements, yet the they won’t take effect until rendered on screen at least once.
I have to select each page manually, after setting all graphs to use XamlRenderSurface, so each would be rendered on screen at least once before the export.

My question is: How can I export XamlRenderSurfaces that are off-screen and haven’t been rendered on-screen before the export process?

You can find an image below showcasing the problem.

Thank you and looking forward to your reply!

Best Regards,
Kaloyan Krastev