DevCorner

Silverlight 3 Quick Tip: Multitouch support on Windows 7

Silverlight 3 supports Multitouch on Windows 7.

Touch class –provides input information and resides in System.Windows.Input namespace

“FrameReported” event - fired when touch action occurs. Event arguments provide the following info:

• Timestamp: identify the touch event by time
• GetTouchPoints function (over specific UI Element)
• GetPrimaryTouchPoint function (over specific UIElement)
• SuspendMousePromotionUntilTouchUp function
• GetTouchPoints returns TouchPointCollection

In TouchPointCollection first point in the collection is the PrimaryPoint. Each member in collection is TouchPoint. TouchPoint provides following info:

• Position
• Size
• TouchDevice
• Action

Action is from TouchAction enumeration

• Up
• Down
• Move

TouchDevice provides the following info

• Id: identification provided by operation system
• DirectlyOver: topmost UIElement under the point

Sample code for getting touch points and simple manipulation:

//Somewhere in code – subscription for touch events:
Touch.FrameReported += new TouchFrameEventHandler(Touch_FrameReported);

When event arrives:

void Touch_FrameReported(object sender, TouchFrameEventArgs e)
    {
      TouchPointCollection points = e.GetTouchPoints(null);
      TouchPoint primaryPoint = e.GetPrimaryTouchPoint(null);

      if (null != primaryPoint)
      {
        if (primaryPoint.Action == TouchAction.Down)
          e.SuspendMousePromotionUntilTouchUp();

        switch (primaryPoint.Action)
        {
          case TouchAction.Down:
            //Business logic here...
            break;

          case TouchAction.Up:
            //Business logic here...
            break;

          case TouchAction.Move:
            //Business logic here...
            break;
        }
      }

Now you application responds for touch events (if you lucky owned of touch-enabled computer) running Windows 7 :)

Enjoy,

Alex