GNU bug report logs - #13399
24.3.50; Word-wrap can't wrap at zero-width space U-200B

Previous Next

Full log

View this message in rfc822 format

From: martin rudalics <rudalics <at> gmx.at>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 13399 <at> debbugs.gnu.org
Subject: bug#13399: 24.3.50; Word-wrap can't wrap at zero-width space U-200B
Date: Fri, 11 Jan 2013 09:16:45 +0100

>> As can be seen in the window showing *foo*,
>> lines are not regularly wrapped at that character.
>
> You mean, not wrapped at all.  Witness the continuation bitmaps in the
> fringes, which shouldn't appear when a line is wrapped.

I thought these bitmaps appear when a line is wrapped.

> If anything, this is a missing feature, since word-wrap is explicitly
> coded to break lines only on SPC and TAB characters.

The doc-string of `word-wrap' says

  When word-wrapping is on, continuation lines are wrapped at the space
  or tab character nearest to the right window edge

Since U-200B is a space character the line should wrap at it.  Also

  this character is intended for invisible word separation and for line
  break control; it has no width, but its presence between two
  characters does not prevent increased letter spacing in justification

and Emacs apparently does handle it specially since it reserves a few
pixels when drawing it.  But documentation on `word-wrap' is scarce ...

> See the
> IT_DISPLAYING_WHITESPACE macro in xdisp.c.

I tried to understand the code but failed.

> If we want to add more characters to the set, we should probably
> arrange a special char-table for this, and have it exposed to Lisp, so
> it could be customized.  Patches are welcome.

IIUC all breakable spaces are between U-2000 and U-200B so maybe a
character table is not needed.

Anway, exposing displayed text to Lisp would be great.  We'd just need
two functions - one that gets the pixel width of an arbitrary buffer
string wrt a specific window, and one that gets the pixel height of an
arbitrary buffer string (newlines ignored) wrt a specific window.  This
way we could get rid of lots of problems currently hidden in the display
engine ...

martin

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.