Redo functionality on InkCanvas

Question

I am using the InkCanvas and InkToolBar in windows 10 build 14939 to capture user ink strokes.

I would like to do a custom button with Undo/Redo however I have trouble to create the following:

private static InkStroke CreateStroke(List<InkPoint> redoInkPoints) {
     var strokeBuilder = new InkStrokeBuilder();
     Matrix3x2 matr = new Matrix3x2();
     return strokeBuilder.CreateStrokeFromInkPoints(redoInkPoints, matr);
}

However visual studio complaints about the matr variable of

'Argment type 'System.Numerics.Matrix3x2' is not assignable to parameter type 'Windows.Foundation.Numerics.Matrix3x2'

even though I don't have anywhere in my code behind referencing the windows.foundation.numerics.matrix3x2.

Anyone got any idea or example on how I use the CreateStrokeFromInkPoints?

Answer 1

According to your code, I think the problem here is that you've used wrong matrix in InkStrokeBuilder.CreateStrokeFromInkPoints method. While using Matrix3x2 matr = new Matrix3x2();, you are creating a zero matrix. It would collapse all your points into a singularity, which is not a valid value here. To fix this issue, you may use System.Numerics.Matrix3x2.Identity property which represents the identity matrix. And following is a simple sample:

XAML:

<StackPanel>
    <InkCanvas x:Name="inkCanvas" Width="500" Height="200" />
    <Button Click="Button_Click">Add a stroke</Button>
</StackPanel>

Code-behind:

private void Button_Click(object sender, RoutedEventArgs e)
{
    List<InkPoint> inkPoints = new List<InkPoint> { new InkPoint(new Point(10, 10), 0.5f), new InkPoint(new Point(100, 100), 0.5f) };

    InkStroke stroke = CreateStroke(inkPoints);

    inkCanvas.InkPresenter.StrokeContainer.AddStroke(stroke);
}

private static InkStroke CreateStroke(List<InkPoint> redoInkPoints)
{
    var strokeBuilder = new InkStrokeBuilder();
    System.Numerics.Matrix3x2 matr = System.Numerics.Matrix3x2.Identity;
    return strokeBuilder.CreateStrokeFromInkPoints(redoInkPoints, matr);
}