Firefox scrolling is abrupt

[lisa761]

Sometimes, while casually scrolling through data-sets in Firefox the rendering messes up the order of visible rows. For instance, you would be at 155th row, but due to the rendering of next set and deletion of previous one, the first visible row changes. Sometimes this change is as significant as 10 rows. This does not seem to be the case in chrome (as significantly).

This probably requires better calculations for the scroll position.