bug#4469: 23.1; visual-line-fringe-indicators w/ 80 column lines

bug#4469: 23.1; visual-line-fringe-indicators w/ 80 column lines

[Reiner Steib]

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Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

Consider the following file with line of exactly 80 columns:

$ cat 80columns
12345678901234567890123456789012345678901234567890123456789012345678901234567890
line 2...01234567890123456789012345678901234567890123456789012345678901234567890
line 3...01234567890123456789012345678901234567890123456789012345678901234567890

$ emacs-23-1 -geometry 80x10 -Q \
  --eval "(setq visual-line-fringe-indicators
            '(left-curly-arrow right-curly-arrow))" 80columns

The the buffer is displayed fine: Three lines that fit into 80 columns
displayed in 3 "visual lines".


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Then do M-x visual-line-mode RET and get this: "visual line breaks"
are inserted.  The buffer is displayed as 6 "visual lines".


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In fact, I now notice that setting visual-line-fringe-indicators is
irrelevant for the bug.

With ...

$ emacs-23-1 -geometry 80x10 -Q 80columns -f visual-line-mode

... I get:


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As the lines fit into 80 columns, visual-line-mode should not insert
"visual line breaks".

In GNU Emacs 23.1.1 (i686-pc-linux-gnu, GTK+ Version 2.12.9)
 of 2009-07-30 on primula
Windowing system distributor `The X.Org Foundation', version 11.0.10400090
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  visual-line-mode: t
  transient-mark-mode: t

Recent input:
<help-echo> M-x v i s <tab> u <tab> <return> M-x r 
e p o r t - e m a c s - b u g <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...
Visual-Line mode enabled

Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/

bug#4469: 23.1; visual-line-fringe-indicators w/ 80 column lines

[Lars Magne Ingebrigtsen]

Reiner Steib <reinersteib+gmane@imap.cc> writes:

> As the lines fit into 80 columns, visual-line-mode should not insert
> "visual line breaks".

I can confirm that this issue is still in Emacs 24.

It seems like a simple off-by-one error to me.  A line with 80 columns
in an 80-column wide Emacs gets a visual line break, while you'd expect
that to happen at 81 columns instead.  Wouldn't you?

-- 
(domestic pets only, the antidote for overdose, milk.)
  bloggy blog http://lars.ingebrigtsen.no/

bug#4469: 23.1; visual-line-fringe-indicators w/ 80 column lines

[Eli Zaretskii]

> From: Lars Magne Ingebrigtsen <larsi@gnus.org>
> Date: Sun, 18 Sep 2011 10:28:39 +0200
> 
> It seems like a simple off-by-one error to me.  A line with 80 columns
> in an 80-column wide Emacs gets a visual line break, while you'd expect
> that to happen at 81 columns instead.  Wouldn't you?

It isn't an off-by-one.  You want the overflow-newline-into-fringe
feature together with word-wrap, but this combination was never
implemented.  I will try to see if it can be easily added, but don't
hold your breath.

If it isn't easy, we will have to mark it "wishlist" and leave it
alone for now.