bug#1425: Longlines mode not preserving text properties

[Peter Seibel]

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the emacs-pretest-bug@gnu.org mailing list.

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

I have some code that applies text properties via the
write-region-annotate-functions and after-insert-file-functions
mechanism in a major mode that also uses longlines-mode. When my text
properties span a soft newline longlines mode doesn't preserve them
when it converts spaces to newlines and back.

The following patch seems to fix my problem but perhaps someone who
groks longlines mode could come up with a more elegant solution.

--- longlines.el.orig   2008-11-24 14:50:17.000000000 -0800
+++ longlines.el        2008-11-24 14:58:22.000000000 -0800
@@ -240,7 +240,7 @@
 If wrapping is performed, point remains on the line.  If the line does
 not need to be wrapped, move point to the next line and return t."
   (if (longlines-set-breakpoint)
-      (progn (insert-before-markers ?\n)
+      (progn (insert-before-markers-and-inherit ?\n)
             (backward-char 1)
              (delete-char -1)
             (forward-char 1)
@@ -347,7 +347,13 @@
       (goto-char (min beg end))
       (while (search-forward "\n" reg-max t)
         (unless (get-text-property (match-beginning 0) 'hard)
-          (replace-match " ")))
+         (let* ((pos (match-beginning 0))
+                (props (text-properties-at pos nil)))
+           (replace-match " ")
+           (let* ((hard-start (member 'hard props))
+                  (after-hard (cddr hard-start))
+                  (newprops (nconc (ldiff props hard-start) after-hard)))
+           (set-text-properties pos (1+ pos) newprops) nil))))
       (set-buffer-modified-p mod)
       end)))


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In GNU Emacs 22.0.99.1 (powerpc-apple-darwin8.9.0, Carbon Version 1.6.0)
 of 2007-05-06 on beagle
Windowing system distributor `Apple Inc.', version 10.4.11
configured using `configure  '--without-x' '--prefix=/usr/local''

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
  locale-coding-system: iso-8859-1
  default-enable-multibyte-characters: t

Major mode: Coders at Work Editing

Minor modes in effect:
  longlines-mode: t
  encoded-kbd-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-services-mode: t
  erc-ring-mode: t
  erc-pcomplete-mode: t
  erc-netsplit-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-autojoin-mode: t
  smart-quote-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  use-hard-newlines: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
n s SPC m e c h a n i s m . C-a M-q <down> <down> C-e
SPC I t SPC a l s o <M-backspace> <M-backspace> <backspace>
<backspace> SPC i n SPC a SPC m a j o r SPC m o d e
SPC t h a t SPC a l s o SPC u s e s SPC l o n g l i
n e s SPC m o d e . SPC T h e SPC M-b M-b <backspace>
- C-e t e x t SPC p r o p e r t i e s SPC M-b M-b M-b
C-k W h e n SPC m y SPC m e <backspace> <backspace>
t e x t SPC p r o p e r t i e s SPC s p a n SPC a SPC
s o f t SPC n e w l i n e SPC M-q C-a C-e SPC l o n
g <M-backspace> t h e SPC <M-backspace> l o n g l i
n e s SPC m o d e SPC M-b M-b C-e M-b C-e d o e s n
' t SPC p r e s e r v e SPC t h e m SPC w h e n SPC
i t SPC c o n v e r t s SPC s p a c e s SPC t o SPC
n e w l i n e s SPC a n d SPC b a c k . M-q C-a C-e
SPC <backspace> C-v C-v M-v M-v C-v M-< <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <up> <up> <down> C-SPC <up> <up> <up> <up> <up>
M-w C-x k <return> M-x r e p o r t <tab> <return>

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-- 
Peter Seibel
http://www.codersatwork.com/
http://www.gigamonkeys.com/blog/