* bug#19496: 25.0.50; term.c, produce_composite_glyh, cmp->pixel_width uninitialized
@ 2015-01-03 14:20 Stephen C. Gilardi
2015-01-03 18:17 ` Eli Zaretskii
0 siblings, 1 reply; 3+ messages in thread
From: Stephen C. Gilardi @ 2015-01-03 14:20 UTC (permalink / raw)
To: 19496
emacs -Q
open an emacs lisp file that contains (lambda ... )
turn on prettify-symbols-mode
the lambda form is converted to (λ ... ), and should be displayed that way, but instead it's displayed as
(\
λ
...)
This commit is the first on master to show the problem: 20791069fa34b486c018ba7f27982bdc6ad2a4ea (found by git bisect)
The problem is the calculation of the pixel_width of the composition in the buffer. It's set to the pixel_width of the composition in the composition table, but that field is not initialized. (There is no mention of pixel_width anywhere in composite.c where the table entries are made.) When I check the value of cmp->pixel_width, it's somewhere near MAX_SHORT. It should be a small integer. Prior to this commit, in my setup, the value is 1 which avoids the problem, but isn't a credible pixel width.
An apparently very wide pixel_width for the composition explains the display anomaly. The composition appears to be thousands of characters wide and if that were true, the anomalous display would have been appropriate.
I don't see an obvious fix. There seems to be some confusing use in the code between "width in columns" and "width in pixels". It's possible that the pixel_width field in "struct it" is not named precisely for how it’s used--in a terminal, the width may actually be used as a number of columns rather than a number of pixels.
In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu)
of 2015-01-03 on localhost
Repository revision: 20791069fa34b486c018ba7f27982bdc6ad2a4ea
System Description: Ubuntu 14.04.1 LTS
Configured using:
`configure --without-x'
Configured features:
SOUND GPM DBUS NOTIFY LIBSELINUX GNUTLS LIBXML2 ZLIB
Important settings:
value of $LANG: en_US.UTF-8
locale-coding-system: utf-8-unix
Major mode: Emacs-Lisp
Minor modes in effect:
diff-auto-refine-mode: t
tooltip-mode: t
global-eldoc-mode: t
electric-indent-mode: t
prettify-symbols-mode: t
menu-bar-mode: t
file-name-shadow-mode: t
global-font-lock-mode: t
font-lock-mode: t
auto-composition-mode: t
auto-encryption-mode: t
auto-compression-mode: t
line-number-mode: t
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Prettify-Symbols mode enabled
user-error: Beginning of history; no preceding item
Load-path shadows:
None found.
Features:
(shadow sort gnus-util mail-extr emacsbug message dired format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns mail-prsvr mail-utils regexp-opt vc-git diff-mode
easymenu easy-mmode xterm time-date tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type tabulated-list newcomment elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow timer select
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 nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process
dbusbind gfilenotify multi-tty emacs)
Memory information:
((conses 16 82152 5459)
(symbols 48 17585 0)
(miscs 40 36 102)
(strings 32 12557 4834)
(string-bytes 1 332483)
(vectors 16 8665)
(vector-slots 8 349036 23681)
(floats 8 65 657)
(intervals 56 259 25)
(buffers 976 12)
(heap 1024 37582 1315))
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#19496: 25.0.50; term.c, produce_composite_glyh, cmp->pixel_width uninitialized
2015-01-03 14:20 bug#19496: 25.0.50; term.c, produce_composite_glyh, cmp->pixel_width uninitialized Stephen C. Gilardi
@ 2015-01-03 18:17 ` Eli Zaretskii
2015-01-03 22:39 ` Paul Eggert
0 siblings, 1 reply; 3+ messages in thread
From: Eli Zaretskii @ 2015-01-03 18:17 UTC (permalink / raw)
To: Stephen C. Gilardi, Paul Eggert; +Cc: 19496
> From: "Stephen C. Gilardi" <scgilardi@gmail.com>
> Date: Sat, 3 Jan 2015 09:20:52 -0500
>
> emacs -Q
> open an emacs lisp file that contains (lambda ... )
> turn on prettify-symbols-mode
> the lambda form is converted to (λ ... ), and should be displayed that way, but instead it's displayed as
> (\
> λ
> ...)
>
> This commit is the first on master to show the problem: 20791069fa34b486c018ba7f27982bdc6ad2a4ea (found by git bisect)
I think that commit was mistaken, and should be reverted, because
before it this worked correctly. CC'ing Paul, who made the change,
and Handa-san, who probably wrote it.
Paul, was there a use case where you saw a problem with the original
code? If so, can you show it?
> I don't see an obvious fix.
Why do you think the previous code is not TRT?
> There seems to be some confusing use in the code between "width in columns" and "width in pixels". It's possible that the pixel_width field in "struct it" is not named precisely for how it’s used--in a terminal, the width may actually be used as a number of columns rather than a number of pixels.
On a text terminal, each glyph is 1 pixel wide. So on a text terminal
these two are identical.
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#19496: 25.0.50; term.c, produce_composite_glyh, cmp->pixel_width uninitialized
2015-01-03 18:17 ` Eli Zaretskii
@ 2015-01-03 22:39 ` Paul Eggert
0 siblings, 0 replies; 3+ messages in thread
From: Paul Eggert @ 2015-01-03 22:39 UTC (permalink / raw)
To: Eli Zaretskii, Stephen C. Gilardi; +Cc: 19496-done
Eli Zaretskii wrote:
> Paul, was there a use case where you saw a problem with the original
> code? If so, can you show it?
Sorry, that was a thinko on my part. I reverted the change in master as commit
5395106. Thanks for reporting it.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-01-03 14:20 bug#19496: 25.0.50; term.c, produce_composite_glyh, cmp->pixel_width uninitialized Stephen C. Gilardi
2015-01-03 18:17 ` Eli Zaretskii
2015-01-03 22:39 ` Paul Eggert
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