[GNC] "Non-sticky" scroll bars in gnucash registers

[Steve Cohen]

For two years something seemed not quite right about the use of scroll 
bars in Gnucash register windows, but I always just "lived with it" in a 
state of vague , not quite conscious annoyance.

I have finally put my finger on the problem.

When I click in the scroller and move my mouse, whenever the mouse 
leaves the scroll bar area the display snaps back to where it was before 
the scroll operation.  I initially tried to carefully keep the mouse 
within the scroll bar area, and that does prevent the display from 
snapping back - but my new ephiphany is this:  If I do manage not to 
stray from the bounds of the scroll bar before releasing the mouse 
button, then the display stays where my scrolling action left it BUT, 
the moment I subsequently move the mouse out of the scroll bar area, the 
display snaps to its previous position.  In particular this makes it 
impossible to edit an entry that was out of the visible scrolling area 
but became visible after scrolling, as it is gone before I can click it. 
  The only way to get to a row not visible is by using the arrow keys or 
PgUp, PgDown.  Ironically, pressing those keys does move the scroller.

I am running GNUCash version 3.900, which I built from source on 
2018-06-03 on Ubuntu 18.04.

This is highly irritating and non-standard behavior, I think.  Other 
apps do not handle scrolling this way, such as the Thunderbird Mail 
inbox, Libre Office Calc, etc.  I was not able to find a setting that 
would govern this behavior.  Do others experience this, or is it a bug?