I've seen this question asked a lot, however, to the opposite of what I'm looking for. While other people want a control to size itself based on the size of text, I'm trying to figure out is if there is a way to grow the size of text to the amount of space available.
Take the idea of a digital clock window and you want the numbers stating the time to grow (or shrink) based on the size of the window the clock is in. If there isn't a way to automatically do this any pointers to a programmatic way I can get this accomplished?
The WPF Viewbox control will grow / shrink its contents to the available space:
http://www.wpftutorial.net/ViewBox.html
Just place your TextBlock within a ViewBox:
<Viewbox Stretch="Uniform" Width="50" Height="50">
<TextBlock Text="Test" />
</Viewbox>
Of course, your Viewbox is typically scaled by its container, but hopefully you get the idea!
来源：https://stackoverflow.com/questions/4794355/how-to-grow-shrink-a-textblock-font-size-to-the-available-space-in-wpf