StylusPlugIn Class

Represents a plug-in that can be added to a control's StylusPlugIns property.

Namespace:  System.Windows.Input.StylusPlugIns
Assembly:  PresentationCore (in PresentationCore.dll)
XMLNS for XAML: Not mapped to an xmlns.

public abstract class StylusPlugIn
This class is not typically used in XAML.

The StylusPlugIn allows you to manipulate StylusPoint objects on separate threads. Separate threads are used so that the ink still renders as the tablet pen inputs data even if the application is doing something else.

To intercept stylus points from the hardware, create a class that inherits from the StylusPlugIn class. The StylusPlugIn class has the following methods that you can override to manipulate StylusPoint objects on a thread in the pen thread pool.

The pen's input is routed to an element's StylusPlugIn on the pen thread. Since 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 make sure the input was routed correctly before performing an operation, subscribe to and perform the operation in the OnStylusDownProcessed, OnStylusMoveProcessed, or OnStylusUpProcessed method. These methods are invoked by the main application thread after accurate hit-testing has been performed. To subscribe to these methods, call the NotifyWhenProcessed method in the method that occurs on the pen thread. For example, if you call NotifyWhenProcessed in OnStylusMove, the OnStylusMoveProcessed occurs.

NoteNote:

If you use a StylusPlugIn inside a control, you should test the plug-in and control extensively to make sure they do not throw any unintended exceptions.

The following example creates a custom StylusPlugIn that constrains the ink to a certain area on the control.

// EventArgs for the StrokeRendered event. 
public class StrokeRenderedEventArgs : EventArgs
{
    StylusPointCollection strokePoints;

    public StrokeRenderedEventArgs(StylusPointCollection points)
    {
        strokePoints = points;
    }

    public StylusPointCollection StrokePoints
    {
        get
        {
            return strokePoints;
        }
    }
}

// EventHandler for the StrokeRendered event. 
public delegate void StrokeRenderedEventHandler(object sender, StrokeRenderedEventArgs e);

// A StylusPlugin that restricts the input area 
class FilterPlugin : StylusPlugIn
{
    StylusPointCollection collectedPoints;
    int currentStylus = -1;
    public event StrokeRenderedEventHandler StrokeRendered;

    protected override void OnStylusDown(RawStylusInput rawStylusInput)
    {
        // Run the base class before modifying the data 
        base.OnStylusDown(rawStylusInput);

        if (currentStylus == -1)
        {
            StylusPointCollection pointsFromEvent = rawStylusInput.GetStylusPoints();

            // Create an emtpy StylusPointCollection to contain the filtered 
            // points.
            collectedPoints = new StylusPointCollection(pointsFromEvent.Description);

            // Restrict the stylus input and add the filtered  
            // points to collectedPoints. 
            StylusPointCollection points = FilterPackets(pointsFromEvent);
            rawStylusInput.SetStylusPoints(points);
            collectedPoints.Add(points);

            currentStylus = rawStylusInput.StylusDeviceId;
        }
    }

    protected override void OnStylusMove(RawStylusInput rawStylusInput)
    {
        // Run the base class before modifying the data 
        base.OnStylusMove(rawStylusInput);

        if (currentStylus == rawStylusInput.StylusDeviceId)
        {
            StylusPointCollection pointsFromEvent = rawStylusInput.GetStylusPoints();

            // Restrict the stylus input and add the filtered  
            // points to collectedPoints. 
            StylusPointCollection points = FilterPackets(pointsFromEvent);
            rawStylusInput.SetStylusPoints(points);
            collectedPoints.Add(points);
        }
    }

    protected override void OnStylusUp(RawStylusInput rawStylusInput)
    {
        // Run the base class before modifying the data 
        base.OnStylusUp(rawStylusInput);

        if (currentStylus == rawStylusInput.StylusDeviceId)
        {
            StylusPointCollection pointsFromEvent = rawStylusInput.GetStylusPoints();

            // Restrict the stylus input and add the filtered  
            // points to collectedPoints. 
            StylusPointCollection points = FilterPackets(pointsFromEvent);
            rawStylusInput.SetStylusPoints(points);
            collectedPoints.Add(points);

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

            currentStylus = -1;
        }
    }

    private StylusPointCollection FilterPackets(StylusPointCollection stylusPoints)
    {
        // Modify the (X,Y) data to move the points  
        // inside the acceptable input area, if necessary 
        for (int i = 0; i < stylusPoints.Count; i++)
        {
            StylusPoint sp = stylusPoints[i];
            if (sp.X < 50) sp.X = 50;
            if (sp.X > 250) sp.X = 250;
            if (sp.Y < 50) sp.Y = 50;
            if (sp.Y > 250) sp.Y = 250;
            stylusPoints[i] = sp;
        }

        // Return the modified StylusPoints. 
        return stylusPoints;
    }

    // This 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)
        {
            StylusPointCollection strokePoints = callbackData as StylusPointCollection;

            if (strokePoints == null)
            {
                return;
            }

            // Raise the StrokeRendered event so the consumer of the plugin can 
            // add the filtered stroke to its StrokeCollection.
            StrokeRenderedEventArgs e = new StrokeRenderedEventArgs(strokePoints);
            OnStrokeRendered(e);
        }

    }

    protected virtual void OnStrokeRendered(StrokeRenderedEventArgs e)
    {
        if (StrokeRendered != null)
        {
            StrokeRendered(this, e);
        }
    }
}

System.Object
  System.Windows.Input.StylusPlugIns.StylusPlugIn
    System.Windows.Input.StylusPlugIns.DynamicRenderer

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0
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