canvas 超出部分自动隐藏

<Canvas x:Name="a" Background="White" Loaded="LayoutRoot_Loaded">

<Canvas.Clip>

<RectangleGeometry RadiusX="5" RadiusY="5" Rect="0,0, 300, 50" />

</Canvas.Clip>

<Canvas.Triggers>

<EventTrigger RoutedEvent="Canvas.Loaded" >

<BeginStoryboard>

<Storyboard x:Name="animation" Storyboard.TargetProperty="(Canvas.Left)" RepeatBehavior="Forever" >

<DoubleAnimation Storyboard.TargetName="ScrollingText" From="0" To="-820" Duration="0:0:20" />

<DoubleAnimation Storyboard.TargetName="ScrollingText2" From="820" To="0" Duration="0:0:20" />

</Storyboard>

</BeginStoryboard>

</EventTrigger>

</Canvas.Triggers>

<TextBlock x:Name="ScrollingText" FontFamily="Comic Sans MS" FontSize="36" Foreground="Green" Text="I have downloaded the moded bios for the x200 which is revision 3.03. The new 3.05 Bios for x200 add some support for Windows 7. " />

<TextBlock x:Name="ScrollingText2" FontFamily="Comic Sans MS" FontSize="36" Foreground="Green" Text="I have downloaded the moded bios for the x200 which is revision 3.03. The new 3.05 Bios for x200 add some support for Windows 7. " />

</Canvas>

启到作用的是canvas.clip