IncrementalHitTester Class

Definition

Dynamically performs hit testing on a Stroke.

C#
public abstract class IncrementalHitTester
Inheritance
IncrementalHitTester
Derived

Examples

The following example demonstrates how to add points to the IncrementalHitTester when the user inputs data with the stylus. The example includes a StrokeHit event handler that erases the part of the Stroke that the user intersects. To create a control that enables a user to erase ink, see How to: Erase Ink on a Custom Control.

C#

// Prepare to collect stylus packets. Get the 
// IncrementalHitTester from the InkPresenter's 
// StrokeCollection and subscribe to its StrokeHitChanged event.
protected override void OnStylusDown(StylusDownEventArgs e)
{
    base.OnStylusDown(e);

    EllipseStylusShape eraserTip = new EllipseStylusShape(3, 3, 0);
    eraseTester = 
        presenter.Strokes.GetIncrementalStrokeHitTester(eraserTip);
    eraseTester.StrokeHit += new StrokeHitEventHandler(eraseTester_StrokeHit);
    eraseTester.AddPoints(e.GetStylusPoints(this));
}

// Collect the StylusPackets as the stylus moves.
protected override void OnStylusMove(StylusEventArgs e)
{
    if (eraseTester.IsValid)
    {
        eraseTester.AddPoints(e.GetStylusPoints(this));
    }
}

// Unsubscribe from the StrokeHitChanged event when the
// user lifts the stylus.
protected override void OnStylusUp(StylusEventArgs e)
{

    eraseTester.AddPoints(e.GetStylusPoints(this));
    eraseTester.StrokeHit -= new
        StrokeHitEventHandler(eraseTester_StrokeHit);
    eraseTester.EndHitTesting();
}

// When the stylus intersects a stroke, erase that part of
// the stroke.  When the stylus dissects a stoke, the 
// Stroke.Erase method returns a StrokeCollection that contains
// the two new strokes.
void eraseTester_StrokeHit(object sender,
    StrokeHitEventArgs args)
{
    StrokeCollection eraseResult =
        args.GetPointEraseResults();
    StrokeCollection strokesToReplace = new StrokeCollection();
    strokesToReplace.Add(args.HitStroke);
   
    // Replace the old stroke with the new one.
    if (eraseResult.Count > 0)
    {
        presenter.Strokes.Replace(strokesToReplace, eraseResult);
    }
    else
    {
        presenter.Strokes.Remove(strokesToReplace);
    }
}

Remarks

The IncrementalHitTester dynamically determines whether the user "hits" a Stroke. This class enables you to provide immediate feedback to the user in situations such as selecting and erasing ink.

There are two classes that inherit from IncrementalHitTester:

The following table lists where to learn how to manage digital ink on a custom control.

To do this… See this article
Create a control that collects digital ink Creating an Ink Input Control
Create a control that enables the user to select ink How to: Select Ink from a Custom Control
Create a control that enables the user to point-erase ink How to: Erase Ink on a Custom Control

XAML Text Usage

This class is not typically used in XAML.

Properties

IsValid

Gets whether the IncrementalHitTester is hit testing.

Methods

AddPoint(Point)

Adds a Point to the IncrementalHitTester.

AddPoints(IEnumerable<Point>)

Adds points to the IncrementalHitTester.

AddPoints(StylusPointCollection)

Adds the specified StylusPoint objects to the IncrementalHitTester.

AddPointsCore(IEnumerable<Point>)

Adds points to the IncrementalHitTester.

EndHitTesting()

Releases resources used by the IncrementalHitTester.

Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
ToString()

Returns a string that represents the current object.

(Inherited from Object)

Applies to

Product Versions
.NET Framework 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
Windows Desktop 3.0, 3.1, 5, 6, 7, 8, 9