bug#34476: fluffy whitespace in the mode-line, despite it running off the screen

[Eli Zaretskii]

> Date: Mon, 10 Aug 2020 17:46:41 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: contovob@tcd.ie, 34476@debbugs.gnu.org
> 
> While doing some further testing, I found a flaw in the implementation
> that I need to resolve before pushing the branch.  I have an idea, but
> I need to test how well it works.

Turns out my original idea of post-processing the glyphs is
unworkable.  The problem I didn't consider is that glyphs are only
produced up to the limit of the window-width, so once the full
mode-line becomes longer than that, any post-processing cannot
recover the glyphs beyond the window edge, because they were never
produced in the first place.

The alternative which I would like to try implementing is to modify
the code of display_string so that it doesn't produce multiple space
glyphs, replacing them with a single glyph, when this option is
non-nil.  Since display_mode_element always calls display_string to
produce the glyphs, this should allow us to solve the problem cleanly.
Stay tuned.