RawStylusInput.NotifyWhenProcessed(Object) Method

Definition

Namespace:

System.Windows.Input.StylusPlugIns

Assembly:

PresentationCore.dll

Subscribes to the application thread's corresponding stylus methods.

public:
 void NotifyWhenProcessed(System::Object ^ callbackData);

public void NotifyWhenProcessed (object callbackData);

member this.NotifyWhenProcessed : obj -> unit

Public Sub NotifyWhenProcessed (callbackData As Object)

Parameters

callbackData

Object

The data to pass to the application thread.

Examples

The following example creates a StylusPlugIn that checks for the Down gesture. The StylusPlugIn calls NotifyWhenProcessed in OnStylusUp to subscribe to the OnStylusUpProcessed method, which is called from the application thread.

class RecognizerPlugin : StylusPlugIn
{
    GestureRecognizer recognizer;
    
    // StylusPointCollection that contains the stylus points of the current
    // stroke.
    StylusPointCollection points;

    // Keeps track of the stylus to check whether two styluses are used on the
    // digitizer.
    int currentStylus;

    public RecognizerPlugin()
        : base()
    {
        recognizer = new GestureRecognizer();
    }

    // Collect the points as the user draws the stroke.
    protected override void OnStylusDown(RawStylusInput rawStylusInput)
    {
        // If points is not null, there is already a stroke taking place
        // on the digitizer, so don't create a new StylusPointsCollection.
        if (points == null)
        {
            points = new StylusPointCollection(rawStylusInput.GetStylusPoints().Description);
            points.Add(rawStylusInput.GetStylusPoints());
            currentStylus = rawStylusInput.StylusDeviceId;
        }
    }

    // Collect the points as the user draws the stroke.
    protected override void OnStylusMove(RawStylusInput rawStylusInput)
    {
        // Check whether the stylus that started the stroke is the same, and
        // that the element hasn't lost focus since the stroke began.
            if (points != null && currentStylus == rawStylusInput.StylusDeviceId)
        {
            points.Add(rawStylusInput.GetStylusPoints());
        }
    }

    // Collect the points as the user draws the stroke.
    protected override void OnStylusUp(RawStylusInput rawStylusInput)
    {
        // Check whether the stylus that started the stroke is the same, and
        // that the element hasn't lost focus since the stroke began.
        if (points != null && currentStylus == rawStylusInput.StylusDeviceId)
        {
            points.Add(rawStylusInput.GetStylusPoints());

            // Subscribe to the OnStylusUpProcessed method.
            rawStylusInput.NotifyWhenProcessed(points);
        }

        points = null;
        currentStylus = 0;
    }
        
    // If the element loses focus, stop collecting the points and don't
    // perform gesture recognition.
    protected override void OnStylusLeave(RawStylusInput rawStylusInput, bool confirmed)
    {
        if (confirmed)
        {
            // Clear the StylusPointCollection
            points = null;
            currentStylus = 0;
        }
    }

    // This method is called on the application thread.
    protected override void OnStylusUpProcessed(object callbackData, bool targetVerified)
    {
        // Check that the element actually receive the OnStylusUp input.
        if (targetVerified && recognizer.IsRecognizerAvailable)
        {
            StylusPointCollection strokePoints = callbackData as StylusPointCollection;

            if (strokePoints == null)
            {
                return;
            }

            // Create a StrokeCollection to pass to the GestureRecognizer.
            Stroke newStroke = new Stroke(strokePoints);
            StrokeCollection strokes = new StrokeCollection();
            strokes.Add(newStroke);

            ReadOnlyCollection<GestureRecognitionResult> results = recognizer.Recognize(strokes);

            // If the GestureRecognizer recognizes the stroke as a Down
            // gesture with strong confidence, raise an event.
            if (results[0].ApplicationGesture == ApplicationGesture.Down &&
                results[0].RecognitionConfidence == RecognitionConfidence.Strong)
            {
                //raise event
            }
        }
    }
}

Class RecognizerPlugin
    Inherits StylusPlugIn
    Private recognizer As GestureRecognizer

    ' StylusPointCollection that contains the stylus points of the current
    ' stroke.
    Private points As StylusPointCollection

    ' Keeps track of the stylus to check whether two styluses are used on the
    ' digitizer.
    Private currentStylus As Integer

    Public Sub New()
        recognizer = New GestureRecognizer()

    End Sub


    ' Collect the points as the user draws the stroke.
    Protected Overrides Sub OnStylusDown(ByVal rawStylusInput As RawStylusInput)

        ' If points is not null, there is already a stroke taking place
        ' on the digitizer, so don't create a new StylusPointsCollection.
        If points Is Nothing Then
            points = New StylusPointCollection(rawStylusInput.GetStylusPoints().Description)
            points.Add(rawStylusInput.GetStylusPoints())
            currentStylus = rawStylusInput.StylusDeviceId
        End If

    End Sub

    ' Collect the points as the user draws the stroke.
    Protected Overrides Sub OnStylusMove(ByVal rawStylusInput As RawStylusInput)

        ' Check whether the stylus that started the stroke is the same, and
        ' that the element hasn't lost focus since the stroke began.
        If Not (points Is Nothing) AndAlso currentStylus = rawStylusInput.StylusDeviceId Then
            points.Add(rawStylusInput.GetStylusPoints())
        End If

    End Sub

    ' Collect the points as the user draws the stroke.
    Protected Overrides Sub OnStylusUp(ByVal rawStylusInput As RawStylusInput)

        ' Check whether the stylus that started the stroke is the same, and
        ' that the element hasn't lost focus since the stroke began.
        If Not (points Is Nothing) AndAlso currentStylus = rawStylusInput.StylusDeviceId Then
            points.Add(rawStylusInput.GetStylusPoints())

            ' Subscribe to the OnStylusUpProcessed method.
            rawStylusInput.NotifyWhenProcessed(points)
        End If

        points = Nothing
        currentStylus = 0

    End Sub

    ' If the element loses focus, stop collecting the points and don't
    ' perform gesture recognition.
    Protected Overrides Sub OnStylusLeave(ByVal rawStylusInput As RawStylusInput, ByVal confirmed As Boolean)

        If confirmed Then
            ' Clear the StylusPointCollection
            points = Nothing
            currentStylus = 0
        End If

    End Sub

    ' This method is called on the application thread.
    Protected Overrides Sub OnStylusUpProcessed(ByVal callbackData As Object, ByVal targetVerified As Boolean)

        ' Check that the element actually receive the OnStylusUp input.
        If targetVerified AndAlso recognizer.IsRecognizerAvailable Then

            Dim strokePoints As StylusPointCollection = callbackData

            If strokePoints Is Nothing Then
                Return
            End If

            ' Create a StrokeCollection to pass to the GestureRecognizer.
            Dim newStroke As New Stroke(strokePoints)
            Dim strokes As New StrokeCollection()
            strokes.Add(newStroke)

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

            ' If the GestureRecognizer recognizes the stroke as a Down
            ' gesture with strong confidence, raise an event.
            If results(0).ApplicationGesture = ApplicationGesture.Down AndAlso _
               results(0).RecognitionConfidence = RecognitionConfidence.Strong Then
                'raise event
            End If
        End If

    End Sub
End Class

Remarks

The pen's input is routed to an element's StylusPlugIn on the pen thread. Because accurate hit-testing cannot be performed on the pen thread, some elements might occasionally receive stylus input intended for other elements. If you need to be sure the input was routed correctly before performing an operation, call the NotifyWhenProcessed method in the method that occurs on the pen thread. The following table lists where to call NotifyWhenProcessed to subscribe to the application thread's method.

Call NotifyWhenProcessed in this method	To subscribe to this method
OnStylusDown	OnStylusDownProcessed
OnStylusMove	OnStylusMoveProcessed
OnStylusUp	OnStylusUpProcessed