WPF Multi-touch tracking touch points - wpf

Question

I'm trying to do a simple application that, when a user touchs a screen, app creates simple point, ellipse, or sth 2d object, and when user moves his finger it should follow, but also when there is a scond touch at the same time new object also has to be created and do the same thing with respect to users movement. Whenever user fingersup, object will be deleted.
To do this, I'm trying to change the touchdrawing code from this link http://www.cookingwithxaml.com/recipes/wpf4/wpf4touch.zip but I couldn't figure out which method should I need to change ?
Can you give advice about that please ?
Thanks.

Answer 1

Here is some sample xaml/C# code that does what I think you want:
MainWindow.xaml:
<Window x:Class="MultitouchExperiments.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Canvas
x:Name="TouchCanvas"
TouchDown="TouchCanvas_TouchDown" TouchUp="TouchCanvas_TouchUp"
TouchMove="TouchCanvas_TouchMove" TouchLeave="TouchCanvas_TouchLeave"
TouchEnter="TouchCanvas_TouchEnter"
VerticalAlignment="Stretch" HorizontalAlignment="Stretch"
Background="Black"
IsManipulationEnabled="True" />
</Grid>
</Window>
MainWindow.xaml.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Diagnostics;
namespace MultitouchExperiments
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
Dictionary<TouchDevice, Ellipse> _Followers = new Dictionary<TouchDevice, Ellipse>();
public MainWindow()
{
InitializeComponent();
}
private void TouchCanvas_TouchDown(object sender, TouchEventArgs e)
{
TouchCanvas.CaptureTouch(e.TouchDevice);
Ellipse follower = new Ellipse();
follower.Width = follower.Height = 50;
follower.Fill = Brushes.White;
follower.Stroke = Brushes.White;
TouchPoint point = e.GetTouchPoint(TouchCanvas);
follower.RenderTransform = new TranslateTransform(point.Position.X, point.Position.Y);
_Followers[e.TouchDevice] = follower;
TouchCanvas.Children.Add(follower);
}
private void TouchCanvas_TouchUp(object sender, TouchEventArgs e)
{
TouchCanvas.ReleaseTouchCapture(e.TouchDevice);
TouchCanvas.Children.Remove(_Followers[e.TouchDevice]);
_Followers.Remove(e.TouchDevice);
}
private void TouchCanvas_TouchMove(object sender, TouchEventArgs e)
{
if (e.TouchDevice.Captured == TouchCanvas)
{
Ellipse follower = _Followers[e.TouchDevice];
TranslateTransform transform = follower.RenderTransform as TranslateTransform;
TouchPoint point = e.GetTouchPoint(TouchCanvas);
transform.X = point.Position.X;
transform.Y = point.Position.Y;
}
}
private void TouchCanvas_TouchLeave(object sender, TouchEventArgs e)
{
//Debug.WriteLine("leave " + e.TouchDevice.Id);
}
private void TouchCanvas_TouchEnter(object sender, TouchEventArgs e)
{
//Debug.WriteLine("enter " + e.TouchDevice.Id);
}
}
}