Peter Lubbers - Pro HTML 5 Programming

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CHAPTER 11 ■ THE FUTURE OF HTML5
Unlike the other mobile device events, the touch events need to represent that there are multiple
points of data—the many potential fingers—present at the same time. As such, the API for touch
handling is a little bit more complex as shown in Listing 11-2.
Listing 11-2. Touch API
function touchMove(event) {
// the touches list contains an entry for every finger currently touching the screen
var touches = event.touches;
// the changedTouches list contains only those finger touches modified at this
// moment in time, either by being added, removed, or repositioned
varchangedTouches = event.changedTouches;
// targetTouches contains only those touches which are placed in the node
// where this listener is registered
vartargetTouches = event.targetTouches;
// once you have the touches you'd like to track, you can reference
// most attributes you would normally get from other event objects
varfirstTouch = touches[0];
varfirstTouchX = firstTouch.pageX;
varfirstTouchY = firstTouch.pageY;
}
// register one of the touch listeners for our example
node.addEventListener("touchmove", touchMove, false);
You may find that the device’s native event handling interferes with your handling of the touch and
gesture events. In those cases, you should make the following call:
event.preventDefault();
This overrides the behavior of the default browser interface and handles the event yourself. Until the
mobile events are standardized, it is recommended that you consult the documentation of the devices
you are targeting with your application.
Peer-to-Peer Networking
We haven’t seen the end of advanced networking in web applications either. With both HTTP and
WebSocket, there is a client (the browser or other user agent) and a server (the host of the URL). Peer-topeer
(P2P) networking allows clients to communicate directly. This is often more efficient than sending
all data through a server. Efficiency, of course, reduces hosting costs and improves application
performance. P2P should make for faster multiplayer games and collaboration software.
Another immediate application for P2P combined with the device element is efficient video chat in
HTML5. In peer-to-peer video chat, conversation partners would be able to send data directly to each
other without routing through a central server. Outside of HTML5, P2P video chat has been wildly
popular in applications like Skype. Because of the high bandwidth required by streaming video, it is
likely that neither of those applications would have been possible without peer-to-peer communication.