bug#14598: 24.3; global-hl-line-mode + text-scale-adjust + next-line + scrolling

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 15 Jun 2013 23:48:51 +0100
> From: E Sabof <esabof@gmail.com>
> Cc: psainty@orcon.net.nz, 14598@debbugs.gnu.org
> 
> > > One way to do it would be for modes to identify themselves, by setting
> > > auto-window-vscroll to t.
> >
> > Then every mode will need to do that.
> >
> 
> The idea is that in practice, the functionality isn't needed most of the
> time, but backfires with text-scale-adjust. The only two modes that I use
> that mix images and text are org-mode and w3m.

There are many more, and I expect more and more to do so.

> > > A perhaps better approach might be to make auto-window-vscroll only act
> > on
> > > lines significantly larger than default height (x4?), and not on any line
> > > with a non-standard height.
> >
> > You need to consider the window height as well (or only that), not
> > just the default font size.  And if we go that way, I'd argue that
> > vscroll should be used regardless of the value of auto-window-vscroll.
> >
> 
> At the moment I'm a bit confused as to how auto-window-vscroll works right
> now. I might try to dig a bit deeper at some point, and put together a
> prototype of how I think it should work.

What do you mean by "how auto-window-vscroll works"?  If you mean how
its value is taken into account, look at line-move-partial.  If you
mean anything else, please ask.