Gesture Handler

The GestureHandler is a component that makes it easy to set up listeners for mouse- and touch-based gestures.

var context = new Famous.createContext('body');
var node = context.addChild();

var DOMElement = require('famous/dom-renderables/DOMElement');
var element = new DOMElement(node);

var GestureHandler = require('famous/components/GestureHandler');
var gestures = new GestureHandler(node);
function callback() { console.log('Gesture'); }
gestures.on('drag', callback);

Currently supported gestures include 'drag', 'tap', 'rotate', and 'pinch'. For touch devices, only up to the first two touches will be accounted for.

Event Payload

Each event callback will receive an object detailing the status ('start', 'move', or 'end') of the gesture, a timestamp, position and velocity information for the first two points of contact and for the center point, and optionally information regarding rotation and scale.

If listeners for 'rotate' and/or 'pinch' are specified, the payload will include .rotation and .scale properties describing the total rotation and scale since the start of the (two-finger) gesture, and delta properties describing the changes since that last time the event was processed. For two-finger gestures, position and velocity information regarding the midpoint of the two pointers will be contained in .center, .centerDelta, and .centerVelocity. For one-finger gestures, these properties will describe the first pointer.

Each payload additionally includes a .points property, describing the number of pointers involved in the gesture, and a .current property describing the number of pointer active immediately after the gesture. For example, in the case that a two-finger 'drag' abruptly ends, leaving no pointers active on the screen, .points will be 2 while .current will be 0.

One such payload is:

    status: "move",
    time: 1432185853220,
    pointers: [
            position: { x: 195, y: 148 },
            delta: { x: 0, y: -2 },
            velocity: { x: 0, y: -111.1111 }
            position: { x: 121, y: 281 },
            delta: { x: -2, y: 2 },
            velocity: { x: -111.1111, y: 111.1111 }
    center: { x: 158, y: 214.5 },
    centerDelta: { x: -1, y: 0 },
    centerVelocity: { x: -55.5555, y: 0 },
    points: 2,
    current: 2,
    taps: 1,
    scale: 1.5261,
    scaleDelta: 0.0302,
    scaleVelocity: 1.6800,
    rotation: 0.0396,
    rotationDelta: -0.0013,
    rotationVelocity: -0.0741

Multi-Tap and Two-Finger-Tap

The payload above includes a .taps property which describes the number of consecutive taps, with each tap falling within a certain configurable threshold of the last. The 'tap' event can be additionally configured to only fire on two-finger taps. To do so, instead of a event name string, one would pass in an options hash as the first parameter to .on:

    event: 'tap',
    points: 2,
    threshold: 100
}, callback);

In the above, callback will only fire for two-finger taps, and .taps in the event payload will be incremented only if consecutive two-finger taps fall within 100ms of each other. By default, .threshold is 250ms.

To implement a double-tap handler, one might do the following in their callback:

function processDoubleTap(e) {
    if (e.taps % 2 === 0) {
        // rest of callback
gestures.on('tap', processDoubleTap);