show-paren-mode indicates mismatch for escaped parentheses

[Ralf Angeli]

In LaTeX escaped parentheses like \(a^2+b^2=c^2\) are used for marking
inline math.  `show-paren-mode' indicates mismatches when moving point
over the opening or closing parentheses.  In order to prevent this, I
think, it should not try to match an escaped paren in the first place.
The following patch achieves this by performing the search for a
matching paren only if an even number of escape chars or none is found
before the character in question:

*** Paren.el    10 Aug 2005 15:24:59 +0200      1.64
--- paren.el    18 Oct 2005 11:28:58 +0200      
***************
*** 144,151 ****
  (defun show-paren-function ()
    (if show-paren-mode
        (let ((oldpos (point))
!           (dir (cond ((eq (syntax-class (syntax-after (1- (point)))) 5) -1)
!                        ((eq (syntax-class (syntax-after (point)))      4) 1)))
            pos mismatch face)
        ;;
        ;; Find the other end of the sexp.
--- 144,158 ----
  (defun show-paren-function ()
    (if show-paren-mode
        (let ((oldpos (point))
!           (dir (cond ((and (eq (syntax-class (syntax-after (1- (point)))) 5)
!                            (zerop (mod (save-excursion
!                                          (backward-char)
!                                          (skip-syntax-backward "\\/")) 2)))
!                       -1)
!                      ((and (eq (syntax-class (syntax-after (point))) 4)
!                            (zerop (mod (save-excursion
!                                          (skip-syntax-backward "\\/")) 2)))
!                       1)))
            pos mismatch face)
        ;;
        ;; Find the other end of the sexp.


In GNU Emacs 22.0.50.1 (i686-pc-linux-gnu, GTK+ Version 2.6.10)
 of 2005-10-18 on neutrino
X server distributor `The X.Org Foundation', version 11.0.60802000
configured using `configure '--with-gtk''

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

Major mode: LaTeX

Minor modes in effect:
  reftex-mode: t
  desktop-save-mode: t
  display-time-mode: t
  iswitchb-mode: t
  recentf-mode: t
  show-paren-mode: t
  encoded-kbd-mode: t
  mouse-wheel-mode: t
  auto-compression-mode: t
  menu-bar-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
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-x C-f s c <tab> v e r b <tab> 8 <tab> <return> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <left> <return> <return> a SPC \ ( b \ ) SPC 
c <right> <left> <left> <left> <left> <up> <right> 
C-x C-s C-x C-f C-a C-k / d a <tab> s h o <tab> <return> 
C-n C-n C-M-x C-x b <return> C-f C-f C-f C-f C-f C-f 
C-f C-f C-f SPC ( d ) SPC e C-b C-b C-b C-b C-b C-b 
C-b C-b C-b C-b C-b C-b C-x C-s M-x r e p o r <tab> 
<return>

Recent messages:
Starting new Ispell process...
Loading reftex...done
Loading reftex-auc...done
Loading reftex-dcr...done
Automatic display of crossref information was turned on
Loading skeleton...done
Wrote /home/angeli/scratch/verbatim-test8.tex
show-paren-function
Wrote /home/angeli/scratch/verbatim-test8.tex
Loading emacsbug...done