bug#19334: 25.0.50; Display bug with zero width fringe

[Eli Zaretskii]

> From: Helmut Eller <eller.helmut@gmail.com>
> Cc: 19334@debbugs.gnu.org
> Date: Wed, 10 Dec 2014 17:45:14 +0100
> 
> On Wed, Dec 10 2014, Eli Zaretskii wrote:
> 
> >> then two lines are used, the last column of the first line is empty, an
> >> arrow appears in the right fringe, and the cursor is displayed in the
> >> second column of the second line.  See attached screenshot.
> >
> > It's a feature: one column is reserved for R2L lines, which will have
> > to show the continuation glyph on the left, because there's no fringe
> > there.
> 
> Apparently not a "pay as you go" feature as I never use R2L lines.

Alas, we don't have a mechanism for adapting the geometry of screen
lines dynamically.  It is calculated when the display of a window
begins, and then used all the way until redisplay of that window is
completed.

If people are annoyed by this "payment", we could perhaps have a
defcustom that would disable the usurpation of that column, but then
people shouldn't complain if/when they see strange effects in R2L
lines (which can happen even if you don't expect them).