Preventing deformation in XAML Grid's background when resizing

Answer 1

I would make it two brushes, one anchored to the right, and one anchored to the left. Something like this:

<Grid>
     <GeometryXXX Geometry="M0,1 0,0 0.4,0 0.45,0.5 0.4,1Z" Width="300" HorizontalAlignment="Left" Brush="#FF6A00">
     <GeometryXXX Geometry="M0,1 0,0 0.4,0 0.45,0.5 0.4,1Z" Width="300" HorizontalAlignment="Right" Brush="#FF0000">
     <TextBlock Foreground="White" VerticalAlignment="Center">Some text</TextBlock>
</Grid>

I don't have my compiler open, and I don't remember the name of the Geometry drawing object.

The other way of doing it would be to create a valueconverter, and do something like:

...
    <GeometryDrawing Geometry="{Binding Width, ValueConverter=LeftAngledThing}" Brush="#FF6A00" />
    <GeometryDrawing Geometry="{Binding Width, ValueConverter=LeftAngledThing}" Brush="#FF0000" />
...

You would need to look up the exact syntax for how to do this though, as I don't remember it right now.