问题描述:

Can someone explain this WPF behaviour?

<Page

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

<Grid>

<!-- Rounded mask -->

<Border Name="mask" VerticalAlignment="Top" Background="Black" CornerRadius="48" Height="400" Width="400" />

<StackPanel>

<!-- Use a VisualBrush of 'mask' as the opacity mask -->

<StackPanel.OpacityMask>

<VisualBrush Visual="{Binding ElementName=mask}" />

</StackPanel.OpacityMask>

<Grid>

<Border Background="Red" Height="400" Width="400"/>

<Border Background="Blue" Height="200" Width="400"/>

</Grid>

</StackPanel>

</Grid>

</Page>

As I would expect, the above code generates the following image (Kaxaml):

alt text http://robbertdam.nl/share/11.png

When I change the line

<Border Background="Blue" Height="200" Width="400"/>

in

<Border Background="Blue" Height="200" Width="600"/>

the image is as follow (didn't expect):

alt text http://robbertdam.nl/share/12.png

The corners are not rounded anymore! This question is actually a "scaled down" example of a problem I'm experiencing in my software, which uses similar masks.

How can I work around this?

网友答案:

Add Stretch="None" to the visual brush.

VisualBrush can (and by default will) stretch the image of the visual it is displaying even if the size of the original visual is fixed.

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