IncrementalHitTester Class
Dynamically performs hit testing on a Stroke.
Assembly: PresentationCore (in PresentationCore.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
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 IncrementalLassoHitTester hit tests strokes by determining whether a lasso path surrounds it.
The IncrementalStrokeHitTester hit tests strokes by determining where an eraser path intersects it.
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 | |
Create a control that enables the user to select ink | |
Create a control that enables the user to point-erase ink |
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.
' 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. Private 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
System.Windows.Ink.IncrementalHitTester
System.Windows.Ink.IncrementalLassoHitTester
System.Windows.Ink.IncrementalStrokeHitTester
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.