Printing in Silverlight 4

We have an application structured roughly like this:

<Grid x:Name="LayoutRoot">
  <ScrollViewer>
<Canvas x:Name="canvas">
  <StackPanel> < Button /><Slider /><Button /></StackPanel>
  <custom:Blob />
  <custom:Blob />
  <custom:Blob />
</Canvas>
  </ScrollViewer>
</Grid>

Each Blob consists of 1 or more rectangles, lines, and text boxes; they are positioned anywhere on the canvas.

If I print the document using the LayoutRoot:

PrintDocument pd = new PrintDocument();
pd += (s, pe) => { pe.PageVisual = LayoutRoot; };
pd.Print("Blobs");

... it is like a print-screen -- the scrollbars, the sliders, the blobs that are visible -- are printed.

If I set PageVisual = canvas, nothing is printed.

How can I get all the blob objects, and just those objects, to print? Do I need to copy them i开发者_运维问答nto another container, and give that container to PageVisual? Can I use a ViewBox to make sure they all fit on one page?

Thanks for any pointers....

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First idea that came to mind while reading your post was the size of your canvas that groups your Blob objects. So found some interesting fragments that might help you:

In addition to specifying the UIElement, you can get the physical size of the print area with the PrintPageEventArgs..::.PrintableArea property. If the UIElement exceeds the PrintableArea, the content will be clipped at the bounds of the PrintableArea. The dimensions of the printable area are in screen-based pixels.

and

You use the PrintPageEventArgs..::.HasMorePages property to print a document with multiple pages. The default for PrintPageEventArgs..::.HasMorePages is false, so it does not need to be set for one-page documents. However, if there are multiple pages to print, you set the PrintPageEventArgs..::.HasMorePages property to true to indicate that there are additional pages to print. You set PrintPageEventArgs..::.HasMorePages back to false in the PrintPage event handler, when the last page is being printed.

Documentation article

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You can apply a scale tranform on the LayoutRoot before printing.

But I have run across a problem where LayoutRoot stays scaled down/up after printing. (Question asked here)