bug#1254: 23.0.60; linum-mode display problem with variable-pitch font

[Chong Yidong <cyd@stupidchicken.com>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> I cannot reproduce the problem with X11 on OSX and thus cannot test
>> this. Would it work to interpret the margin width in terms of the
>> broadest glyph in a font, so other packages would benefit too?
>
> Not only that's not really possible with the current code's limitations,
> but it would also be a bad idea: in most fonts the widest glyph is
> pretty hideously wide, so you'd end up with margins that are much
> too wide.

I looked at this some more.  Apparently, the workaround of making the
linum face fixed pitch doesn't work, because the margin width always
uses the default glyph width.  Apparently, the default glyph width is
too narrow when using some variable-pitch fonts (in my case, DejaVu
Sans).

I don't know any completely satisfactory way to resolve this.  One
possible workaround is for linume.el to provide an option to add an
extra column to the margin width.