The Following Example shows how the PlacementMode enumeration values help you place the Popup window and adjust its position when screen boundaries obscure its content.
PlacementMode = Absolute
A Popup control is positioned relative to the upper-left corner of the screen and offset by the HorizontalOffset and VerticalOffset properties.
PlacementMode = AbsolutePoint
A Popup control is positioned relative to the upper-left corner of the screen and offset by the HorizontalOffset and VerticalOffset properties.
PlacementMode = Bottom
A Popup control is positioned where the control aligns its upper edge with the lower edge of the PlacementTarget and aligns its left edge with the left edge of the PlacementTarget.
If the lower edge of the screen hides all or part of the Popup, the control realigns with the upper edge of the PlacementTarget. If the upper edge of the screen hides all or part of this new position, the control realigns with the lower edge of the screen. After these adjustments, if the control is still partially hidden by the upper edge of the screen, the control realigns with the upper edge of the screen.
PlacementMode = Center
A position of the Popup control where the control centers itself over the PlacementTarget.
