Flick.js revision 16f6ce56ed5f7889fc7449bba668a85f8a39bd84
/**
* The gestures module provides gesture events such as "flick", which normalize user interactions
* across touch and mouse or pointer based input devices. This layer can be used by application developers
* to build input device agnostic components which behave the same in response to either touch or mouse based
* interaction.
*
* <p>Documentation for events added by this module can be found in the event document for the <a href="YUI.html#events">YUI</event> global.</p>
*
* @module event-gestures
*/
/**
* Adds support for a "flick" event, which is fired at the end of a touch or mouse based flick gesture, and provides
* velocity of the flick, along with distance and time information.
*
* @module event-gestures
* @submodule event-flick
*/
var EVENT = ("ontouchstart" in Y.config.win && !Y.UA.chrome) ? {
start: "touchstart",
end: "touchend"
} : {
start: "mousedown",
end: "mouseup"
},
START = "start",
END = "end",
OWNER_DOCUMENT = "ownerDocument",
MIN_VELOCITY = "minVelocity",
MIN_DISTANCE = "minDistance",
PREVENT_DEFAULT = "preventDefault",
_FLICK_START = "_fs",
_FLICK_START_HANDLE = "_fsh",
_FLICK_END_HANDLE = "_feh",
NODE_TYPE = "nodeType";
/**
* Sets up a "flick" event, that is fired whenever the user initiates a flick gesture on the node
* where the listener is attached. The subscriber can specify a minimum distance or velocity for
* which the event is to be fired. The subscriber can also specify if there is a particular axis which
* they are interested in - "x" or "y". If no axis is specified, the axis along which there was most distance
* covered is used.
*
* <p>It is recommended that you use Y.bind to set up context and additional arguments for your event handler,
* however if you want to pass the context and arguments as additional signature arguments to "on",
* you need to provide a null value for the configuration object, e.g: <code>node.on("flick", fn, null, context, arg1, arg2, arg3)</code></p>
*
* @event flick
* @for YUI
* @param type {string} "flick"
* @param fn {function} The method the event invokes. It receives an event facade with an e.flick object containing the flick related properties: e.flick.time, e.flick.distance, e.flick.velocity and e.flick.axis, e.flick.start.
* @param cfg {Object} Optional. An object which specifies any of the following:
* <dl>
* <dt>minDistance (in pixels, defaults to 10)</dt>
* <dd>The minimum distance between start and end points, which would qualify the gesture as a flick.</dd>
* <dt>minVelocity (in pixels/ms, defaults to 0)</dt>
* <dd>The minimum velocity which would qualify the gesture as a flick.</dd>
* <dt>preventDefault (defaults to true)</dt>
* <dd>Can be set to true/false to prevent default behavior as soon as the touchstart/touchend or mousedown/mouseup is received so that things like scrolling or text selection can be
* prevented. This property can also be set to a function, which returns true or false, based on the event facade passed to it.</dd>
* </dl>
* @return {EventHandle} the detach handle
*/
Y.Event.define('flick', {
on: function (node, subscriber, ce) {
var startHandle = node.on(EVENT[START],
this._onStart,
this,
node,
subscriber,
ce);
subscriber[_FLICK_START_HANDLE] = startHandle;
},
detach: function (node, subscriber, ce) {
var startHandle = subscriber[_FLICK_START_HANDLE],
endHandle = subscriber[_FLICK_END_HANDLE];
if (startHandle) {
startHandle.detach();
subscriber[_FLICK_START_HANDLE] = null;
}
if (endHandle) {
endHandle.detach();
subscriber[_FLICK_END_HANDLE] = null;
}
},
processArgs: function(args) {
var params = (args.length > 3) ? Y.merge(args.splice(3, 1)[0]) : {};
if (!(MIN_VELOCITY in params)) {
params[MIN_VELOCITY] = this.MIN_VELOCITY;
}
if (!(MIN_DISTANCE in params)) {
params[MIN_DISTANCE] = this.MIN_DISTANCE;
}
if (!(PREVENT_DEFAULT in params)) {
params[PREVENT_DEFAULT] = this.PREVENT_DEFAULT;
}
Y.log("flick, processArgs : minDistance =" + params.minDistance + ", minVelocity =" + params.minVelocity + ", preventDefault = " + params.preventDefault);
return params;
},
_onStart: function(e, node, subscriber, ce) {
var start = true, // always true for mouse
endHandle,
doc,
preventDefault = subscriber._extra.preventDefault,
origE = e;
if (e.touches) {
start = (e.touches.length === 1);
e = e.touches[0];
}
if (start) {
if (preventDefault) {
// preventDefault is a boolean or function
if (!preventDefault.call || preventDefault(e)) {
origE.preventDefault();
}
}
e.flick = {
time : new Date().getTime()
};
subscriber[_FLICK_START] = e;
endHandle = subscriber[_FLICK_END_HANDLE];
if (!endHandle) {
doc = (node.get(NODE_TYPE) === 9) ? node : node.get(OWNER_DOCUMENT);
endHandle = doc.on(EVENT[END], Y.bind(this._onEnd, this), null, node, subscriber, ce);
subscriber[_FLICK_END_HANDLE] = endHandle;
}
}
},
_onEnd: function(e, node, subscriber, ce) {
var endTime = new Date().getTime(),
start = subscriber[_FLICK_START],
valid = !!start,
endEvent = e,
startTime,
time,
preventDefault,
params,
xyDistance,
distance,
velocity,
axis;
if (valid) {
if (e.changedTouches) {
if (e.changedTouches.length === 1 && e.touches.length === 0) {
endEvent = e.changedTouches[0];
} else {
valid = false;
}
}
if (valid) {
params = subscriber._extra;
preventDefault = params[PREVENT_DEFAULT];
if (preventDefault) {
// preventDefault is a boolean or function
if (!preventDefault.call || preventDefault(e)) {
endEvent.preventDefault();
}
}
startTime = start.flick.time;
endTime = new Date().getTime();
time = endTime - startTime;
xyDistance = [
endEvent.pageX - start.pageX,
endEvent.pageY - start.pageY
];
axis = params.axis || (Math.abs(xyDistance[0]) >= Math.abs(xyDistance[1])) ? 'x' : 'y';
distance = xyDistance[(axis === 'x') ? 0 : 1];
velocity = (time !== 0) ? distance/time : 0;
if (isFinite(velocity) && (Math.abs(distance) >= params[MIN_DISTANCE]) && (Math.abs(velocity) >= params[MIN_VELOCITY])) {
e.type = "flick";
e.flick = {
time:time,
distance: distance,
velocity:velocity,
axis: axis,
start : start
};
ce.fire(e);
}
subscriber[_FLICK_START] = null;
}
}
},
MIN_VELOCITY : 0,
MIN_DISTANCE : 0,
PREVENT_DEFAULT : true
});