event-gestures/js/Flick.js

	Flick.js revision 870b1351b8dad6efd508aacc807cd53dbd43b7c8
// TODO: Better way to sniff 'n' switch touch support?
var TOUCH = "ontouchstart" in Y.config.win,

    TOUCH_EVENT_MAP = {
        start: "touchstart",
        end: "touchend"
    },

    MOUSE_EVENT_MAP = {
        start: "mousedown",
        end: "mouseup"
    },

    EVENT = (TOUCH) ? TOUCH_EVENT_MAP : MOUSE_EVENT_MAP,

    START = "start",
    END = "end",

    OWNER_DOCUMENT = "ownerDocument",
    MIN_VELOCITY = "minVelocity",
    MIN_DISTANCE = "minDistance",

    FLICK_START = "_flickStart",
    FLICK_START_HANDLE = "_flickStartHandle",
    FLICK_END_HANDLE = "_flickEndHandle";

Y.Event.define('flick', {

    init: function (node, subscriber, ce) {

        var startHandle = node.on(EVENT[START],
            Y.bind(this._onStart, this),
            null, // Don't want stuff mixed into the facade
            node,
            subscriber,
            ce);

        node.setData(FLICK_START_HANDLE, startHandle);
    },

    destroy: function (node, subscriber, ce) {

        var startHandle = node.getData(FLICK_START_HANDLE),
            endHandle = node.getData(FLICK_END_HANDLE);

        if (startHandle) {
            startHandle.detach();
            node.setData(FLICK_START_HANDLE, null);
        }

        if (endHandle) {
            endHandle.detach();
            node.setData(FLICK_END_HANDLE, null);
        }
    },

    processArgs: function(args) {
        var params = (args[3]) ? args.splice(3, 1) : {};

        if (!(MIN_VELOCITY in params)) {
            params.minVelocity = this.MIN_VELOCITY;
        }

        if (!(MIN_DISTANCE in params)) {
            params.minDistance = this.MIN_DISTANCE;
        }

        return params;
    },

    _onStart: function(e, node, subscriber, ce) {

        var start = true, // always true for mouse
            endHandle,
            doc;

        if (e.touches) {
            start = (e.touches.length === 1);
            e = e.touches[0];
        }

        if (start) {

            e.preventDefault();

            node.setData(FLICK_START, {
                time : new Date().getTime(),
                pageX: e.pageX,
                pageY: e.pageY,
                clientX: e.clientX,
                clientY: e.clientY
            });

            endHandle = node.getData(FLICK_END_HANDLE);

            if (!endHandle) {
                doc = node.get(OWNER_DOCUMENT);

                endHandle = doc.on(EVENT[END], Y.bind(this._onEnd, this), null, node, subscriber, ce);
                node.setData(FLICK_END_HANDLE,endHandle);
            }
        }
    },

    _onEnd: function(e, node, subscriber, ce) {

        var endTime = new Date().getTime(),
            valid = node.getData(FLICK_START),
            start = valid,
            endEvent = e,

            startTime,
            time,
            params,
            xyDistance,
            distance,
            absDistance,
            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) {

                startTime = start.time;
                endTime = new Date().getTime();
                time = endTime - startTime;

                params = subscriber._extra;

                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];
                absDistance = Math.abs(distance);
                velocity = absDistance/time;

                if (isFinite(velocity) && velocity >= params.minVelocity && absDistance >= params.minDistance) {
                    ce.fire({
                        distance:distance,
                        time:time,
                        velocity:velocity,
                        axis:axis,
                        start: start,
                        end : {
                            time: endTime,
                            clientX: endEvent.clientX,
                            clientY: endEvent.clientY,
                            pageX: endEvent.pageX,
                            pageY: endEvent.pageY
                        }
                    });
                }

                node.setData(FLICK_START, null);
            }
        }
    },

    MIN_VELOCITY : 0,
    MIN_DISTANCE : 10
});