WPF FlowDocument Scale to Fit Page

Question

I have a FlowDocument that varies in height due to an ItemsControl in a BlockUIContainer. In some cases, the ItemsControl extends beyond the page height. Is there a way to scale the FlowDocument to fit a page (8.5" X 11") right before printing if needed?

As of right now, the FlowDocument is named 'doc' and the method for printing I am using is:

private void Print_Click(object sender, RoutedEventArgs e)
    {

        PrintDialog pd = new PrintDialog();
        doc.PageHeight = pd.PrintableAreaHeight;
        doc.PageWidth = pd.PrintableAreaWidth;
        doc.ColumnGap = 0;
        doc.ColumnWidth = pd.PrintableAreaWidth;
        IDocumentPaginatorSource dps = doc;
        pd.PrintDocument(dps.DocumentPaginator, "Sheet");
    }

Answer 1

I know it's a bit late, but here is the solution I came up with.

First, we create a wrapper that will generate the document pages for us. Each page will have a scale transformation applied to it before returning it.

public class FittedDocumentPaginator : DocumentPaginator
{
    public DocumentPaginator Base { get; private set; }
    public double Scale { get; private set; }
    private readonly ScaleTransform _sTransform;

    public FittedDocumentPaginator( DocumentPaginator baseDp, double scale )
    {
        if ( baseDp == null )
            throw new ArgumentNullException( "baseDp" );

        Base = baseDp;
        Scale = scale;
        _sTransform = new ScaleTransform( scale, scale );
    }

    public override DocumentPage GetPage( int pageNumber )
    {
        var page = Base.GetPage( pageNumber );
        ( (ContainerVisual)page.Visual ).Transform = _sTransform;

        return page;
    }

    public override bool IsPageCountValid
    {
        get { return Base.IsPageCountValid; }
    }

    public override int PageCount
    {
        get { return Base.PageCount; }
    }

    public override Size PageSize
    {
        get { return Base.PageSize; }
        set { Base.PageSize = value; }
    }

    public override IDocumentPaginatorSource Source
    {
        get { return Base.Source; }
    }
}

Using it is fairly simple:

    private void PrintDocument( PrintDialog pd, FlowDocument document, double scale, string title )
    {
        DocumentPaginator dp = ( (IDocumentPaginatorSource)document ).DocumentPaginator;
        FittedDocumentPaginator fdp = new FittedDocumentPaginator( dp, scale );

        pd.PrintDocument( fdp, title );
    }

If you're interested, here is how we determined the scale. In our case, the document was extended past the page width, but it can easily be modified to accommodate the page height.

    private void Print( FlowDocument document, string title, double documentWidth )
    {
        var pd = new PrintDialog();

        if ( pd.ShowDialog() == true )
        {
            // Set the printing margins.
            Thickness pageMargins = document.PagePadding;
            document.PagePadding = new Thickness( 15.0 );

            // In our case, the document's width is NaN so we have to navigate the visual tree to get the ActualWidth, which is represented by 'documentWidth'.
            double scale = documentWidth / pd.PrintableAreaWidth;

            if ( scale < 1.0 )
            {
                // The report fits on the page just fine. Don't scale.
                scale = 1.0;
            }

            double invScale = 1 / scale;

            document.PageHeight = pd.PrintableAreaHeight * scale;
            document.PageWidth = pd.PrintableAreaWidth * scale;

            DocumentPaginator dp = ( (IDocumentPaginatorSource)document ).DocumentPaginator;
            FittedDocumentPaginator fdp = new FittedDocumentPaginator( dp, invScale );

            pd.PrintDocument( fdp, title );

            // Restore the original values so the GUI isn't altered.
            document.PageHeight = Double.NaN;
            document.PageWidth = Double.NaN;
            document.PagePadding = pageMargins;
        }
    }