Private Function InterpretScratchoutGesture(ByVal stroke As Stroke) As Boolean
    ' Attempt to instantiate a recognizer for scratchout gestures.
    Dim gestures() As ApplicationGesture = {ApplicationGesture.ScratchOut}

    Dim recognizer As New GestureRecognizer(gestures)

    If Not recognizer.IsRecognizerAvailable Then
        Return False
    End If

    ' Determine if the stroke was a scratchout gesture.
    Dim gestureStrokes As StrokeCollection = New StrokeCollection()
    gestureStrokes.Add(stroke)

    Dim results As ReadOnlyCollection(Of GestureRecognitionResult)
    results = recognizer.Recognize(gestureStrokes)

    If results.Count = 0 Then
        Return False
    End If

    ' Results are returned sorted in order strongest-to-weakest; 
    ' we need only analyze the first (strongest) result.
    If (results(0).ApplicationGesture = ApplicationGesture.ScratchOut) Then

        ' Use the scratchout stroke to perform hit-testing and 
        ' erase existing strokes, as necessary.
        Return True
    Else
        ' Not a gesture: display the stroke normally.
        Return False
    End If
End Function