bug#9698: 24.0.90; Inserting 0x2215 produces 0x29F5

bug#9698: 24.0.90; Inserting 0x2215 produces 0x29F5

[Eli Zaretskii]

 Type: a C-x 8 RET 2215 RET b

 You will see the expected: a∕b

 Now type: א C-x 8 RET 2215 RET ב

 And you will see something entirely different: א∕ב

 There's a glyphless character displayed between the two letters whose
 code is 0x29F5 (or at least that's what Emacs shows in the empty
 rectangle on my system; YMMV if you have a different font set).
 Interestingly enough, "C-x =" claims that both characters are 0x2215
 and are displayed using the same font...

Bug or feature?  If a feature, what is the intent here?


In GNU Emacs 24.0.90.1 (i386-mingw-nt5.1.2600)
 of 2011-09-26 on HOME-C4E4A596F7
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4)'

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: ENU
  value of $XMODIFIERS: nil
  locale-coding-system: cp1255
  default enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  desktop-save-mode: t
  show-paren-mode: t
  display-time-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  temp-buffer-resize-mode: t
  line-number-mode: t

Recent input:
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <C-end> C-w <return> 
R u n SPC . / a u t o g e n . s h <switch-frame> <switch-frame> 
, SPC a n d SPC B o b ' s SPC y o u r SPC u n c l e 
. <return> <C-home> C-c C-s <switch-frame> d d d d 
d d d d C-z C-z C-z C-z C-z C-z C-z C-z C-z C-z C-z 
C-z C-z C-z C-z C-z C-z C-z C-z M-: ( g e t - c h a 
r - c o d e - p r o p e r t y SPC # x 2 2 1 5 SPC ' 
b i d i - c l a s s ) <return> M-: <up> <C-right> <C-right> 
<C-right> <C-right> <C-right> <backspace> <backspace> 
<backspace> <backspace> 2 f <return> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <up> <C-right> <C-right> <C-right> <C-right> 
<C-right> <C-right> <C-right> <C-right> <C-right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <left> <left> 
<right> C-x = <left> <left> <left> <right> <right> 
<right> C-SPC <right> <left> <left> C-SPC <right> <right> 
M-w <left> C-SPC <right> M-w C-x b f o o <return> <return> 
a C-y b <return> <return> <language-change> א C-y ב 
<right> <right> <left> <up> <up> <up> <down> <right> 
<up> <right> C-x = <left> <right> <right> <right> <right> 
<right> <left> <delete> C-x 8 <return> 2 2 1 5 <return> 
<left> <return> <up> <left> C-x = <up> <right> <down> 
<down> M-x ר ק פ ם ר א <backspace> <backspace> <backspace> 
<backspace> <backspace> <backspace> <language-change> 
r e p o r t - e m <tab> <return>

Recent messages:
Sending...
Added to d:/usr/eli/rmail/SENT.MAIL
Sending email...done
Sending...done
ON
CS
Char: ∕ (8725, #o21025, #x2215, file ...) point=2180 of 3183 (68%) column=53
Mark set [5 times]
Char: ∕ (8725, #o21025, #x2215) point=3 of 9 (22%) column=1
Char: ∕ (8725, #o21025, #x2215) point=8 of 10 (70%) column=1
byte-code: End of buffer

Load-path shadows:
None found.

Features:
(shadow emacsbug iso-transl find-func multi-isearch help-mode view
utf-7 dabbrev rmailout network-stream starttls tls smtpmail
auth-source eieio assoc gnus-util password-cache mailalias sendmail
ld-script dired-x dired tcl parse-time nxml-uchnm rng-xsd xsd-regexp
rng-cmpct rng-nxml rng-valid rng-loc rng-uri rng-parse nxml-parse
rng-match rng-dt rng-util rng-pttrn nxml-ns nxml-mode nxml-outln
nxml-rap nxml-util nxml-glyph nxml-enc xmltok sgml-mode arc-mode
archive-mode generic conf-mode newcomment org-wl org-w3m org-vm
org-rmail org-mhe org-mew org-irc org-jsinfo org-infojs org-html
org-exp ob-exp org-exp-blocks org-agenda org-info org-gnus org-docview
org-bibtex bibtex org-bbdb org byte-opt warnings bytecomp byte-compile
cconv macroexp advice help-fns advice-preload ob-emacs-lisp ob-tangle
ob-ref ob-lob ob-table org-footnote org-src ob-comint ob-keys ob
ob-eval org-pcomplete pcomplete org-list org-faces org-compat
org-entities org-macs cal-menu calendar cal-loaddefs gud comint ring
noutline outline easy-mmode make-mode sh-script executable cc-awk
add-log autorevert info flyspell ispell vc-cvs jka-compr vc-bzr
cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles cc-align
cc-engine cc-vars cc-defs regexp-opt qp rmailsum rmailmm message
format-spec rfc822 mml easymenu mml-sec mm-decode mm-bodies mm-encode
mailabbrev gmm-utils mailheader mail-parse rfc2231 rmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils desktop server
filecache saveplace midnight generic-x paren battery time time-date
tooltip ediff-hook vc-hooks lisp-float-type mwheel dos-w32 disp-table
ls-lisp w32-win w32-vars tool-bar dnd fontset image fringe lisp-mode
register page menu-bar rfn-eshadow timer select scroll-bar mouse
jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer loaddefs button faces cus-face files text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process multi-tty
emacs)

bug#9698: 24.0.90; Inserting 0x2215 produces 0x29F5

[Eli Zaretskii]

> Date: Fri, 07 Oct 2011 20:30:37 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> 
>  Type: a C-x 8 RET 2215 RET b
> 
>  You will see the expected: a∕b
> 
>  Now type: א C-x 8 RET 2215 RET ב
> 
>  And you will see something entirely different: א∕ב

A similar thing happens on GNU/Linux on a TTY: after typing א ∕, the
first 2 characters, the display is as expected.  But as soon as I type
the 3rd character, ב,the ∕ disappears and in its stead appears an
empty rectangle, which "C-x =" claims is 0x2215.

bug#9698: 24.0.90; Inserting 0x2215 produces 0x29F5

[Eli Zaretskii]

tags 9698 notabug
stop

> Date: Fri, 07 Oct 2011 20:30:37 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> 
> Bug or feature?  If a feature, what is the intent here?

Answering my own question: a feature.  This is due to the fact that
0x2215 is a mirrored character, and its mirror image is 0x29F5; see
admin/unidata/BidiMirroring.txt.  Emacs behaves as intended here, and
mirrors the character when it is in right-to-left context.

Closing the bug.