bug#27008: 26.0.50; auto-hscroll-mode and scroll-left

[Eli Zaretskii]

> From: Stephen Berman <stephen.berman@gmx.net>
> Cc: 27008@debbugs.gnu.org
> Date: Wed, 31 May 2017 16:18:26 +0200
> 
> There is one minor issue: with auto-hscroll-mode set to `current-line'
> and (scroll-left 32 t), when I scroll vertically by holding down <down>
> or C-n or <up> or C-p, the motion is less smooth than usual.  With the
> same auto-hscroll-mode setting but no scroll-left, vertical scrolling is
> smoother, but still not as smooth as with auto-hscroll-mode set to t or
> nil (with either of these settings, vertical scrolling seems slightly
> less smooth with (scroll-left 32 t) than with no scroll-left, though the
> difference is less noticeable than with auto-hscroll-mode set to
> current-line).

The display engine is working harder when this mode is on, and some
optimizations are disabled.  I didn't see a way of implementing this
that would avoid more expensive redisplay.  Sorry.

> But I don't think this is a serious annoyance, so unless you see an
> easy fix for it, I think you should commit the patch as is to
> master.

OK, thanks, will do.