Find ancestor in DataTemplate

Question

I'm trying to show popup on DataTemplate element TextEdit (from DevExpress), according to this and this topics I created something like that:

<DataTemplate x:Key="SomeTemplate">
    <dxe:TextEdit x:Name="SomeTextEdit" Text="{Binding DisplayText, Mode=OneWay}" 
                    EditMode="InplaceInactive">
        <dxe:TextEdit.ContextMenu>
            <ContextMenu/>
        </dxe:TextEdit.ContextMenu>
        <Popup PlacementTarget="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type dxe:TextEdit}}}" IsOpen="{Binding IsKeyboardFocused, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type dxe:TextEdit}}, Mode=OneWay}">
            <TextBlock Background="White">
                <TextBlock.Text>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</TextBlock.Text>
            </TextBlock>
        </Popup>
    </dxe:TextEdit>
</DataTemplate>

And it don't work, in Diagnostic Tool Events window I get message:

Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='DevExpress.Xpf.Editors.TextEdit', AncestorLevel='1''. BindingExpression:(no path); DataItem=null; target element is 'Popup' (Name=''); target property is 'PlacementTarget' (type 'UIElement')

Why is that?

Answer 1

Popup will use different VisualTree and we cannot use RelativeSource binding method to find element from main VisualTree.Still you can set PlacementTarget via ElementName binding. You can use like this,

<Popup IsOpen="{Binding PlacementTarget.IsKeyboardFocused, RelativeSource={RelativeSource Mode=Self},Mode=OneWay}" PlacementTarget="{Binding ElementName=SomeTextEdit}">
    <TextBlock Background="White" Text="Hi" />
</Popup>