Erratic behavior if "Cursor Surrounding Lines" > 0 and/or "Smooth Scrolling" is set

[gasparschott]

If the Editor pref "Cursor Surrounding Lines" is set to be greater than 0 (e.g., 6 lines) and/or if "Smooth Scrolling" is set, sync scrolling gets confused and results in erratic up and down scrolling or continued scrolling in one or both panes even after the user has stopped actively scrolling. I encountered a similar problem in a split editor HTML project I was working on; in my case it was a rounding issue in the math when working with the height of iframe/textarea elements and the scroll position. My solution was to round numbers to at most 1 or 2 decimal places.