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PreviewMouseDown does not tunnel as expected

I have the following tree in my application:

MainWindow (Window)
> LayoutRoot (Grid)
  > (MyCustomControl)
    > Item1 (Grid)
      > Button (Button1)

MyCustomControl comes from ItemsControl and displays its items on a StackPanel.

MyCustomControl needs to know when the mouse clicked inside of itself, so I overridden the OnPreviewMouseDown method and expect to find out about any mouse click inside my control.

What happens: if I click inside Button1, the PreviewMouseDown event moves along the tree, and OnPreviewMouseDown is executed as expected. But if I click on Item1, the PreviewMouseDown event will stop right after MainWindow and won't even reach LayoutRoot.

Here are the details of the routed events I received with Snoop :

Click Button1:

(Window)
> (Border)
  > (AdornerDecorator)
    > (ContentPresenter)
      > LayoutRoot (Grid)
        > (MyCustomControl)
          > (Border)
            > (StackPanel)
              > Item1 (Grid)
                > Button1 (Button)
                  > Chrome (ButtonChrome)

Click on item 1:

(Window)
> (Border)

, , .

?

+3
1

, . ControlTemplate, :

<ControlTemplate>
    <ItemsPresenter />
</ControlTemplate>

. ControlTemplate, :

<ControlTemplate>
    <Border Background="{TemplateBinding Background}" ...>
        <ItemsPresenter />
    </Border>
</ControlTemplate>

, Background NULL, . Background Transparent, .

- - ( ), , .

+4

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