Attached Card Shadow and Canvas

[michael-hawker]

@Ryken100 I was playing around to try and test #4587 and noticed another behavior. It may just be related to the oddity of non-templated controls needing a container, but it was a bit odd, so I wanted to check with you first.

If I have a Grid and a Rectangle like so:

<Grid>
      <Rectangle x:Name="Element"
              Height="100"
              Width="100"
              Fill="Red"
              RadiusX="32" RadiusY="32">
        <ui:Effects.Shadow>
          <media:AttachedCardShadow BlurRadius="8"
                                    CornerRadius="32"
                                    Color="Black"
                                    Offset="4,4"
                                    Opacity="1"/>
        </ui:Effects.Shadow>
      </Rectangle>
</Grid>

(Or even just a rectangle by itself on the page without the grid,) the shadow works fine:

However, if I use a Canvas instead, it doesn't work:

    <Canvas>
      <Rectangle x:Name="Element"
              Height="100"
              Width="100"
              Fill="Red"
              Canvas.Top="100"
              Canvas.Left="100"
              RadiusX="32" RadiusY="32">
        <ui:Effects.Shadow>
          <media:AttachedCardShadow BlurRadius="8"
                                    CornerRadius="32"
                                    Color="Black"
                                    Offset="4,4"
                                    Opacity="1"/>
        </ui:Effects.Shadow>
      </Rectangle>
    </Canvas>

If I then wrap the Rectangle in a Border it works again:

    <Canvas>
      <Border Canvas.Top="100" Canvas.Left="100">
      <Rectangle x:Name="Element"
              Height="100"
              Width="100"
              Fill="Red"
              RadiusX="32" RadiusY="32">
        <ui:Effects.Shadow>
          <media:AttachedCardShadow BlurRadius="8"
                                    CornerRadius="32"
                                    Color="Black"
                                    Offset="4,4"
                                    Opacity="1"/>
        </ui:Effects.Shadow>
      </Rectangle>
      </Border>
    </Canvas>

Thoughts?