isScrollInProgress

Whether a scroll block currently holds the position, for a caller that shows or disables something while the pane is traveling.

It is true from the moment a block takes the position - a step before the block's first line, since it waits there for the block it took the position from to unwind - until that block returns or is ended. It answers that and nothing more: the user's own scrolling arrives as discrete wheel and keyboard events with neither a start nor an end, so it is not an interval to report.