How to: Specify a Custom Popup Position

This example shows how to specify a custom position for a Popup control when the Placement property is set to Custom.

When the Placement property is set to Custom, the Popup calls a defined instance of the CustomPopupPlacementCallback delegate. This delegate returns a set of possible points that are relative to the top left corner of the target area and the top left corner of the Popup. The Popup placement occurs at the point that provides the best visibility.

The following example shows how to define the position of a Popup by setting the Placement property to Custom. It also shows how to create and assign a CustomPopupPlacementCallback delegate in order to position the Popup. The callback delegate returns two CustomPopupPlacement objects. If the Popup is hidden by a screen edge at the first position, the Popup is placed at the second position.

 <Popup Name="popup1"  
        PlacementTarget ="{Binding ElementName=myButton}" 
        Placement="Custom">
  <TextBlock Height="60" Width="200" 
             Background="LightGray"
             TextWrapping="Wrap">Popup positioned by using
  CustomPopupPlacement callback delegate</TextBlock>
</Popup>
public CustomPopupPlacement[] placePopup(Size popupSize,
                                           Size targetSize,
                                           Point offset)
{
    CustomPopupPlacement placement1 =
       new CustomPopupPlacement(new Point(-50, 100), PopupPrimaryAxis.Vertical);

    CustomPopupPlacement placement2 =
        new CustomPopupPlacement(new Point(10, 20), PopupPrimaryAxis.Horizontal);

    CustomPopupPlacement[] ttplaces =
            new CustomPopupPlacement[] { placement1, placement2 };
    return ttplaces;
}
popup1.CustomPopupPlacementCallback =
    new CustomPopupPlacementCallback(placePopup);

For the complete sample, see Popup Placement Sample.

Reference

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