Silverlight : Visibility of the content overflowing off a custom panel

Question

Hi there,

I just wrote a custom panel, name it MyList, working more or less like a simple List. I use it into an ItemControl as an ItemsPanel. The grid surrounding my ItemsControl got a width of x If MyList got a width of X too, its childs (elements) will overflow (as a div style overflow visible in html), but if it width is explictly > x, its childs are not visible outside my list (as expected) (as a div style overflow hidden in html).

I double checked values from MeasureOverride and ArrangeOverride and they are invariably thoses affected to MyPanel, the ItemTemplate.

I never understand how Silverlight decides when overflow is visible or hidden, but especially in this case, it's weird !