problem with scrolling horizontal for mac users with 2-finger gesture swiping left and right: stutters and not smooth.
digged around and found the cause of problem at line 1568 on github sly.js
scrolling.curDelta = ((o.horizontal ? event.deltaY || event.deltaX : event.deltaY) || -event.wheelDelta);
appears to be working correctly when changed to
scrolling.curDelta = ((o.horizontal ? event.deltaX : event.deltaY) || -event.wheelDelta);
hope this is helpful ^^