bug#24169: 25.1.50; Line numbers disappear when horizontally scrolled

[Eli Zaretskii]

> From: ivan <ivan.brennan@gmail.com>
> Date: Sat, 6 Aug 2016 12:02:09 -0400
> 
> Using linum-mode displays line numbers to the left of the left fringe. I 
> would expect them to remain visible
> regardless of any horizontal scrolling, since that's how the left fringe 
> behaves (not to mention numerous other
> editors and applications). However, when using line-truncation, the line 
> numbers disappear when the text is
> horizontally scrolled. I think this is worth fixing, because it would be more 
> useful and look better (the dead
> space takes up screen real-estate and makes me sad).

It's a bug in the design of linum-mode: it puts the overlay that
displays the line numbers on the first character of each line.  So
when that first character is not displayed, the overlay is not shown
either.

A possible fix would be to move the overlay to the first visible
character after the horizontal scroll.  Patches welcome.

Thanks.