all files / src/plugin/ GestureMgr.js

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var GestureMgr = function () {
 
    this._track = [];
};
 
GestureMgr.prototype = {
 
    constructor: GestureMgr,
 
    recognize: function (event, target, root) {
        this._doTrack(event, target, root);
        return this._recognize(event);
    },
 
    clear: function () {
        this._track.length = 0;
        return this;
    },
 
    _doTrack: function (event, target, root) {
        var touches = event.targetTouches;
 
        if (!touches) {
            return;
        }
 
        var trackItem = {
            points: [],
            touches: [],
            target: target,
            event: event
        };
 
        for (var i = 0, len = touches.length; i < len; i++) {
            var touch = touches[i];
            trackItem.points.push([touch.clientX, touch.clientY]);
            trackItem.touches.push(touch);
        }
 
        this._track.push(trackItem);
    },
 
    _recognize: function (event) {
        for (var eventName in recognizers) {
            if (recognizers.hasOwnProperty(eventName)) {
                var gestureInfo = recognizers[eventName](this._track, event);
                if (gestureInfo) {
                    return gestureInfo;
                }
            }
        }
    }
};
 
function dist(pointPair) {
    var dx = pointPair[1][0] - pointPair[0][0];
    var dy = pointPair[1][1] - pointPair[0][1];
 
    return Math.sqrt(dx * dx + dy * dy);
}
 
function center(pointPair) {
    return [
        (pointPair[0][0] + pointPair[1][0]) / 2,
        (pointPair[0][1] + pointPair[1][1]) / 2
    ];
}
 
var recognizers = {
 
    pinch: function (track, event) {
        var trackLen = track.length;
 
        if (!trackLen) {
            return;
        }
 
        var pinchEnd = (track[trackLen - 1] || {}).points;
        var pinchPre = (track[trackLen - 2] || {}).points || pinchEnd;
 
        if (pinchPre
            && pinchPre.length > 1
            && pinchEnd
            && pinchEnd.length > 1
        ) {
            var pinchScale = dist(pinchEnd) / dist(pinchPre);
            !isFinite(pinchScale) && (pinchScale = 1);
 
            event.pinchScale = pinchScale;
 
            var pinchCenter = center(pinchEnd);
            event.pinchX = pinchCenter[0];
            event.pinchY = pinchCenter[1];
 
            return {
                type: 'pinch',
                target: track[0].target,
                event: event
            };
        }
    }
};
 
export default GestureMgr;