IncrementalHitTester Class

Dynamically performs hit testing on a Stroke.

Namespace: System.Windows.Ink
Assembly: PresentationCore (in presentationcore.dll)
XML Namespace:  http://schemas.microsoft.com/winfx/2006/xaml/presentation

'Declaration
Public MustInherit Class IncrementalHitTester
'Usage
Dim instance As IncrementalHitTester

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

The IncrementalHitTester dynamically determines whether the user "hits" a Stroke. This class allows 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

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 allows a user to erase ink, see How to: Erase Ink on a Custom Control.


' Prepare to collect stylus packets. Get the 
' IncrementalHitTester from the InkPresenter's 
' StrokeCollection and subscribe to its StrokeHitChanged event.
Protected Overrides Sub OnStylusDown(ByVal e As StylusDownEventArgs)

    MyBase.OnStylusDown(e)

    Dim eraserTip As New EllipseStylusShape(3, 3, 0)
    eraseTester = presenter.Strokes.GetIncrementalStrokeHitTester(eraserTip)
    AddHandler eraseTester.StrokeHit, _
        AddressOf eraseTester_StrokeHit
    eraseTester.AddPoints(e.GetStylusPoints(Me))

End Sub 'OnStylusDown

' Collect the StylusPackets as the stylus moves.
Protected Overrides Sub OnStylusMove(ByVal e As StylusEventArgs)

    If eraseTester.IsValid Then
        eraseTester.AddPoints(e.GetStylusPoints(Me))
    End If

End Sub 'OnStylusMove

' Unsubscribe from the StrokeHitChanged event when the
' user lifts the stylus.
Protected Overrides Sub OnStylusUp(ByVal e As StylusEventArgs)

    eraseTester.AddPoints(e.GetStylusPoints(Me))

    RemoveHandler eraseTester.StrokeHit, _
        AddressOf eraseTester_StrokeHit
    eraseTester.EndHitTesting()
   
End Sub 'OnStylusUp


' 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.
Sub eraseTester_StrokeHit(ByVal sender As Object, _
        ByVal args As StrokeHitEventArgs)

    Dim eraseResult As StrokeCollection = _
        args.GetPointEraseResults()
    Dim strokesToReplace As New StrokeCollection()
    strokesToReplace.Add(args.HitStroke)

    ' Replace the old stroke with the new one.
    If eraseResult.Count > 0 Then
        presenter.Strokes.Replace(strokesToReplace, eraseResult)
    Else
        presenter.Strokes.Remove(strokesToReplace)
    End If

End Sub 'eraseTester_StrokeHit 


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 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0

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