Resize container without resizing text controls - wpf

Question

I have a Custom Control containing a Canvas placed inside a Viewbox. This allows me to resize the control and everything inside the Canvas scales beautifully.
Much to my annoyance a requirement to stop any scaling of text within the control has reared its head. All other controls (mainly graphics) should scale, but not text. Text should move to the correct place upon resize, but the font should remain the same.
Any ideas how to do this?

Answer 1

After much head scratching I found a relatively simple workaround.
As I'm not going to need to click on any text in the control I've put all graphics inside one canvas with zOrder 1 and all text in another with zorder 0. Then I put them inside a grid so they overlap:
<ControlTemplate TargetType="{x:Type local:ContourPlot}">
<Border Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}">
<Grid>
<Viewbox>
<Border BorderBrush="Black" BorderThickness="1">
<Canvas x:Name="cvGraph" Width="{TemplateBinding Width}" Height="{TemplateBinding Height}" >
<Rectangle Canvas.Left="40" Canvas.Top="31" Width="48" Height="41" Fill="AliceBlue"/>
</Canvas>
</Border>
</Viewbox>
<Canvas Width="{TemplateBinding Width}" Height="{TemplateBinding Height}" >
<Label x:Name="lblTest" Canvas.Left="0" Canvas.Top="10" Content="Label" FontSize="12" />
</Canvas>
</Grid>
</Border>
</ControlTemplate>