I can’t find the previous question about the UserPopup. IIRC you were asking about the placement properties.
This is how it works:
The popup closes automatically when the user clicks outside of the popup or a control outside is activated. You can also close it by calling Close(). The Closed even fires when the popup is closed.
It’s a useful control to create complex input widgets, especially if used in conjunction with the tool icons that all input controls accept.