Window.LayoutTransform -> Why doesn't this work?

<Window x:Class="scaletest.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="scaletest" Height="300" Width="300"
>
<Window.LayoutTransform>
<ScaleTransform CenterX="0.5" CenterY="0.5" ScaleX="2" ScaleY="2" />
</Window.LayoutTransform>
<StackPanel>
<Button>test</Button>
</StackPanel>
</Window>

Why does the scale transform doesn't do anything? If I put the same transform on the stackpanel.layouttransform, it works, but that's not what i want.

[790 byte] By [Simon] at [2007-12-24]