Re: Line number in mode-line with column-number-mode on in GNU Emacs 23.x

[Eli Zaretskii <eliz@gnu.org>]

> From: Peter Dyballa <Peter_Dyballa@Web.DE>
> Date: Fri, 25 Dec 2009 11:51:58 +0100
> 
> In compilation mode it happens that the line number is substituted to  
> "??" although I've set line-number-display-limit to nil, i.e., GNU  
> Emacs should not stop counting. I also set line-number-display-limit- 
> width (first) to 625, although some lines can be as long as a few  
> 10,000 characters (later set to 62,500, but no change).

The code seems to remember that a window had long lines, and once that
happens, this window will not have line numbers, until you switch to
another buffer.  Is that your case -- that you enlarged
line-number-display-limit-width only _after_ you saw "??" instead of a
line number?  If so, does it help to switch to a different buffer and
then switch back to the original one in the same window?

Failing that, I don't see any explanation for what you report.
Perhaps try stepping with a debugger through decode_mode_spec, or
submit a bug report with a clear recipe to reproduce this behavior.

> Is there a way to force display of the line number?

I don't see one, except enlarging line-number-display-limit-width to a
very large number (but not too large -- Emacs multiplies it by about
100 (depending on your window height), and if the result overflows,
you get the opposite of what you wanted.

Maybe we should allow nil as a value, meaning unlimited line width.

> Is it suppressed because of duration of high CPU load?

This code runs during redisplay, so it's not a good idea for it to be
too slow.  But I never profiled this, so I have no idea if it really
can be slow for long lines.