bug#24633: highlight-region func using (window-hscroll) in :align-to spec can cause inf loop

[Eli Zaretskii <eliz@gnu.org>]

> From: npostavs@users.sourceforge.net
> Cc: 24633@debbugs.gnu.org
> Date: Sat, 22 Oct 2016 15:27:42 -0400
> 
> I tried adding a counter in redisplay_internal, it prevents having a
> tight loop in C.  Actually, the behaviour becomes like the split window
> case: there is additional hscrolling each time the cursor blinks, but it
> can be interrupted with C-g.  That seems adequate behaviour to me, what
> do you think?

Did you see what happens when blink-cursor-mode is turned off?  (If
that's what you meant by "each time the cursor blinks; if not, what
caused it to blink?)

The patch looks OK to me, so if it gives better results than locking
up Emacs with the current code, let's push it to master.

> > Do you really think that a formal grammar, whether accurate/complete
> > or not, is a good way of describing a feature?
> 
> The formal grammar plus the informal description of what the parts mean
> seems a perfectly fine description for _this_ feature.

Not to me, not anywhere close to being fine.  For starters, Emacs Lisp
programmers don't have to be proficient in reading formal grammars.
But that's me.

Thanks.