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How to: Specify a Custom Popup Position

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

Example

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.

XAML 
 <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>
C# 
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;
}
C# 
popup1.CustomPopupPlacementCallback =
    new CustomPopupPlacementCallback(placePopup);

For the complete sample, see Popup Placement Sample.

See also