core/src/ons/gesture-detector.js
function getRotation(start, end) {
    // need two fingers
    if (start.length >= 2 && end.length >= 2) {
      return this.getAngle(end[1], end[0]) - this.getAngle(start[1], start[0]);
    }
    return 0;
  }
function getRotation(start, end) {
    // need two fingers
    if (start.length >= 2 && end.length >= 2) {
      return this.getAngle(end[1], end[0]) - this.getAngle(start[1], start[0]);
    }
    return 0;
  }
function getRotation ( start , end ) { // need two fingers if ( start . length >= 2 && end . length >= 2 ) { return this . getAngle ( end [ 1 ] , end [ 0 ] ) - this . getAngle ( start [ 1 ] , start [ 0 ] ) ; } return 0 ; }
calculate the rotation degrees between two touchLists
@param {Array} start array of touches
@param {Array} end array of touches
@return {Number} rotation
calculate the rotation degrees between two touchLists