Note: these are early notes based on some initial experiments with the Silverlight 5 beta, apply a pinch of salt to what you read.

You’ll find a new class in the Silverlight 5 beta framework called the RichTextBoxOverflow – this is a really simple but really clever idea in that you can set up a RichTextBox and then you can tell it to overflow any content that doesn’t fit into that textbox into a RichTextBoxOverflow. It really is that simple so something along the lines of;

  <Grid
    x:Name="LayoutRoot"
    Background="White">
    <Grid.ColumnDefinitions>
      <ColumnDefinition />
      <ColumnDefinition />
    </Grid.ColumnDefinitions>
    <RichTextBox
      OverflowContentTarget="{Binding ElementName=overflow}" />
    <RichTextBoxOverflow
      Grid.Column="1"
      x:Name="overflow" />
  </Grid>

and you can (sort of) see the effect below as I fill the first RichTextBox and the content flows into the second one;

I took this a little bit further and spend 20 mins or so putting together a simple sample that allows for dynamic addition of RichTextBoxOverflows with a limited amount of support for dragging them around on the screen. Here it is running in the page;