How To: Recognize Application Gestures

The following example demonstrates how to erase ink when a user makes a ScratchOut gesture on an InkCanvas. This example assumes an InkCanvas, called inkCanvas1, is declared in the XAML file.

Example

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Ink;
using System.Collections.ObjectModel;

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();

        if (inkCanvas1.IsGestureRecognizerAvailable)
        {
            inkCanvas1.EditingMode = InkCanvasEditingMode.InkAndGesture;
            inkCanvas1.Gesture += new InkCanvasGestureEventHandler(inkCanvas1_Gesture);
            inkCanvas1.SetEnabledGestures(
                new ApplicationGesture[] { ApplicationGesture.ScratchOut });
        }
    }

    void inkCanvas1_Gesture(object sender, InkCanvasGestureEventArgs e)
    {
        ReadOnlyCollection<GestureRecognitionResult> gestureResults =
            e.GetGestureRecognitionResults();

        // Check the first recognition result for a gesture.
        if ((gestureResults[0].RecognitionConfidence ==
            RecognitionConfidence.Strong) &&
           (gestureResults[0].ApplicationGesture ==
            ApplicationGesture.ScratchOut))
        {
            StrokeCollection hitStrokes = inkCanvas1.Strokes.HitTest(
                                            e.Strokes.GetBounds(), 10);

            if (hitStrokes.Count > 0)
            {
                inkCanvas1.Strokes.Remove(hitStrokes);
            }
        }
    }
}

Imports System
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Ink
Imports System.Collections.ObjectModel

Class Window1
    Inherits Window

    Public Sub New()
        InitializeComponent()

        If inkCanvas1.IsGestureRecognizerAvailable Then
            inkCanvas1.EditingMode = InkCanvasEditingMode.InkAndGesture
            AddHandler inkCanvas1.Gesture, AddressOf inkCanvas1_Gesture
            inkCanvas1.SetEnabledGestures(New ApplicationGesture() {ApplicationGesture.ScratchOut})
        End If

    End Sub 'New

    Sub inkCanvas1_Gesture(ByVal sender As Object, ByVal e As InkCanvasGestureEventArgs) 

        Dim gestureResults As ReadOnlyCollection(Of GestureRecognitionResult) = _
                              e.GetGestureRecognitionResults()
        
        ' Check the first recognition result for a gesture.
        If gestureResults(0).RecognitionConfidence = _
           RecognitionConfidence.Strong AndAlso _
           gestureResults(0).ApplicationGesture = _
           ApplicationGesture.ScratchOut Then

            Dim hitStrokes As StrokeCollection = _
                inkCanvas1.Strokes.HitTest(e.Strokes.GetBounds(), 10)

            If hitStrokes.Count > 0 Then
                inkCanvas1.Strokes.Remove(hitStrokes)
            End If
        End If
    
    End Sub 'inkCanvas1_Gesture
End Class 'Window1

See Also

Reference

ApplicationGesture
InkCanvas
Gesture