sketchShear.js

function distortLayer(layer, shearHorizontallyBy, shearVerticallyBy) {
  var shearVerticallyBy = shearVerticallyBy || 0;
  if(!layer.isKindOfClass(MSShapeGroup)) return;
  var path=layer.bezierPathWithTransforms();
  var transform=DKDistortionTransform.transformWithInitialRect(layer.frame().rect());
  transform.shearHorizontallyBy(shearHorizontallyBy);
  transform.shearVerticallyBy(shearVerticallyBy);
  var nextPath = transform.transformBezierPath(path);
  layer.setBezierPath(nextPath);
  doc.reloadInspector();
}

function shearByDegree(layer, angle) {
  var offset=(Math.sqrt(Math.pow(layer.frame().height()/Math.cos(angle * (Math.PI/180)),2)-Math.pow(layer.frame().height(),2)))/2;
  return (angle<0) ? -offset : offset;
}