bug#29053: 26.0.90: scroller cannot be dragged to bottom of window

[charles@aurox.ch (Charles A. Roelli)]

> Date: Sun, 29 Oct 2017 14:22:06 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> CC: 29053@debbugs.gnu.org
> Reply-to: Eli Zaretskii <eliz@gnu.org>
> 
> > Date: Sun, 29 Oct 2017 13:00:14 +0100
> > From: charles@aurox.ch (Charles A. Roelli)
> > 
> > In comparison, when doing the same from 26.0.90 (a recent build --
> > 4189d0e, 2017-10-29), the scrolling lags about 2 seconds behind
> > (possibly another issue)
> 
> Almost certainly another issue.  It is best to visit the file with
> find-file-literally to be sure.

Thanks for suggesting that.  There is no scroll lag when visiting the
file literally, and the main issue introduced in this bug report
persists.

> > and I cannot bring the scroller to the
> > bottom of the window -- I only reach "98% L32461".  Actually, the
> > mouse pointer tracking seems to be off by some vertical pixel offset,
> > such that if I click and drag the scroller, when the mouse pointer
> > reaches halfway down the scroll bar, the scroller is not under it, but
> > only 40% or 45% down.
> 
> This seems to be toolkit-specific -- on MS-Windows, I see no such
> issues: I can scroll to the last line and even beyond (the last
> display is with EOB on the topmost line).

Under NS I had the same behavior until 26.0.90.  I will bisect to see
where the problem was introduced.