https://www.wien2002.at/plugins/magiczoomplus/classes/magictoolbox.utils.js

1function onMagicTap(e) {
2    var mzObj = e.getTarget(),
3        tap = {
4            id: e.changedTouches[0].identifier,
5            ts: e.timeStamp,
6            x: e.changedTouches[0].clientX,
7            y: e.changedTouches[0].clientY
8        },
9        tap0;
10    while ( mzObj && 'a' !== mzObj.tagName.toLowerCase() ) {
11        mzObj = mzObj.parentNode;
12    }
13    if (!mzObj) {
14        return;
15    }
16
17    if ( 'touchstart' == e.type ) {
18        mzObj.tap = tap;
19    } else if ( 'touchend' == e.type ) {
20        tap0 = mzObj.tap;
21        mzObj.tap = null;
22        if (!tap0) {
23            return;
24        };
25
26        if (tap.id === tap0.id && tap.ts - tap0.ts <= 200
27            && Math.sqrt(Math.pow(tap.x-tap0.x,2) + Math.pow(tap.y-tap0.y,2)) <= 15
28        ) {
29            e.stop();
30            if (mzObj.onclick) {
31                mzObj.onclick();
32            };
33            return;
34        }
35    }
36}