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StrokeCollection.HitTest Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Indicates whether a specified StylusPointCollection intersects with a StrokeCollection object.

Namespace:  System.Windows.Ink
Assembly:  System.Windows (in System.Windows.dll)

Syntax

'Declaration
Public Function HitTest ( _
    stylusPointCollection As StylusPointCollection _
) As StrokeCollection

public StrokeCollection HitTest(
    StylusPointCollection stylusPointCollection
)

Parameters

Return Value

Type: System.Windows.Ink.StrokeCollection
A StrokeCollection that contains the strokes that intersect with the points in the specified StylusPointCollection.

Remarks

Consider a StrokeCollection named MyStrokes that contain strokes S0 - S2, and a StylusPointCollection named MySPC that contains points P0 - P3. The following illustration shows the position of these strokes and points.

Hit-Test for StrokeCollection

If you make the following HitTest call, the returned StrokeCollection contains S1 and S2.

MyStrokes.HitTest(MySPC)

Examples

The following code demonstrates the HitTest method. If you draw a stroke that intersects an existing stroke collection, the color of the existing stroke changes to red.

Run this sample

<Canvas>
    <Rectangle Height="500" Width="500" Stroke="Black" Margin="50,50,0,0" />
    <InkPresenter x:Name="MyIP" Height="500" Width="500" Background="Transparent" Margin="50,50,0,0"
              MouseLeftButtonDown="MyIP_MouseLeftButtonDown"
              MouseMove="MyIP_MouseMove"
              LostMouseCapture="MyIP_LostMouseCapture" />
</Canvas>

    Private MyStroke As Stroke

    Public Sub New()
        MyBase.New()
        InitializeComponent()
        SetBoundary()
    End Sub

    'A new stroke object, MyStroke, is created and is added to the StrokeCollection object
    'of the InkPresenter, MyIP
    Private Sub MyIP_MouseLeftButtonDown(ByVal sender As Object, ByVal e As MouseEventArgs)
        MyIP.CaptureMouse()
        Dim MyStylusPointCollection As StylusPointCollection = New StylusPointCollection
        MyStylusPointCollection.Add(e.StylusDevice.GetStylusPoints(MyIP))
        MyStroke = New Stroke(MyStylusPointCollection)
        MyStroke.DrawingAttributes.Color = Colors.Yellow
        MyStroke.DrawingAttributes.Width = 8
        MyIP.Strokes.Add(MyStroke)
    End Sub

    'StylusPoint objects are collected from the MouseEventArgs and added to MyStroke.
    Private Sub MyIP_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs)
        If (Not (MyStroke) Is Nothing) Then
            MyStroke.StylusPoints.Add(e.StylusDevice.GetStylusPoints(MyIP))
            Dim HitStrokes As StrokeCollection = New StrokeCollection
            HitStrokes = MyIP.Strokes.HitTest(e.StylusDevice.GetStylusPoints(MyIP))
            'Change the color of the strokes that the new strokes intersects with.
            Dim i As Integer = 0
            Do While (i _
                        < (HitStrokes.Count - 1))
                HitStrokes(i).DrawingAttributes.Color = Colors.Red
                i = (i + 1)
            Loop
        End If
    End Sub

    'MyStroke is completed
    Private Sub MyIP_LostMouseCapture(ByVal sender As Object, ByVal e As MouseEventArgs)
        MyStroke = Nothing
    End Sub


Stroke MyStroke;

//A new stroke object named MyStroke is created. MyStroke is added to the StrokeCollection of the InkPresenter named MyIP
private void MyIP_MouseLeftButtonDown(object sender, MouseEventArgs e)
{
    MyIP.CaptureMouse();

    StylusPointCollection MyStylusPointCollection = new StylusPointCollection();
    MyStylusPointCollection.Add(e.StylusDevice.GetStylusPoints(MyIP));

    MyStroke = new Stroke(MyStylusPointCollection);
    MyStroke.DrawingAttributes.Color = Colors.Yellow;
    MyStroke.DrawingAttributes.Width = 8;

    MyIP.Strokes.Add(MyStroke);
}

//StylusPoint objects are collected from the MouseEventArgs and added to MyStroke.
private void MyIP_MouseMove(object sender, MouseEventArgs e)
{
    if (MyStroke != null)
    {
        MyStroke.StylusPoints.Add(e.StylusDevice.GetStylusPoints(MyIP));
        StrokeCollection HitStrokes = new StrokeCollection();
        HitStrokes = MyIP.Strokes.HitTest(e.StylusDevice.GetStylusPoints(MyIP));
        //Change the color of the strokes that the new strokes intersects with.
        for (int i = 0; i < HitStrokes.Count - 1; i++)
        {
            HitStrokes[i].DrawingAttributes.Color = Colors.Red;
        }

    }
}

//MyStroke is completed
private void MyIP_LostMouseCapture(object sender, MouseEventArgs e)
{
    MyStroke = null;
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.