Viewbox
The Viewbox element
automatically scales its content to fill the space available. Strictly
speaking, Viewbox is not a panel—it
derives from Decorator. This means
that unlike most panels, it can have only one child. However, its
capability to adjust the size of its content in order to adapt to its
surroundings makes it a useful layout tool.
Figure 3-22 shows a window that
doesn't use a Viewbox but probably
should. The window's content is a Canvas containing a rather small drawing.
Example 3-19 shows the markup.

Figure 3-22. Canvas without Viewbox
Example 3-19. Canvas without Viewbox
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<Canvas Width="18" Height="18" VerticalAlignment="Center">
<Ellipse Canvas.Left="1" Canvas.Top="1" Width="16" Height="16"
Fill="Yellow" Stroke="Black" />
<Ellipse Canvas.Left="4.5" Canvas.Top="5" Width="2.5" Height="3"
Fill="Black" />
<Ellipse Canvas.Left="11" Canvas.Top="5" Width="2.5" Height="3"
Fill="Black" />
<Path Data="M 5,10 A 3,3 90 0 0 13,10" Stroke="Black" />
</Canvas>
</Window>We can use a Viewbox to resize
the content automatically. It will expand it to be large enough to fill
the space, as shown in Figure 3-23. (If
you're wondering why the drawing doesn't touch the edges of the window,
it's because the Canvas is slightly
larger than the drawing it contains.)
Figure 3-23. Canvas with Viewbox
All we had to do to get ...