Tries to scroll e by x and y pixel, make the smooth scrolling animation last duration milliseconds
Scroll continuously until scrollstop is called.
Pass an x and y velocity, or just a y velocity.
If only a single arg is passed, it will be treated as y (vertical scroll).
Can also pass a multiplier, intented to be used as a numeric arg when :scrollstart is bound to a key.
Velocity unit = px/second
Call after scrollstart() to cease scrolling.
Tries to find a node which can be scrolled either x pixels to the right or y pixels down among the Elements in {nodes} and children of these Elements.
This function used to be recursive but isn't anymore due to various attempts at optimizing the function in order to reduce GC pressure.