bug#21363: 25.0.50; Some characters confuse display

bug#21363: 25.0.50; Some characters confuse display

[Richard Stallman]

This text from a message to emacs-devel

   AVGVSTÓ·SACR·
   A·A·LV́CIꟾ·A·FꟾLIꟾ·MEN·
   PROCVLVS·ET·IV́LIÁNVS·
   P · S ·
   DÉDICÁTIÓNE·DECVRIÓNIBVS·ET·
   AVGVSTÁLIBVS·CÉNAM·DEDÉRVNT

confuses display on my Linux console.
If you go to the second line of the text and type C-e,
the cursor appears on the final middledot.

I've seen other strange things happen just moving around on that text,
such as displaying lines in the wrong place, but I can't
reproduce them.




In GNU Emacs 25.0.50.1 (i686-pc-linux-gnu, GTK+ Version 2.24.23)
 of 2015-08-12 on freetop
Repository revision: 79a169684dfad2c0bbb9fdbae539c1f30d9f0ac3
System Description:	Trisquel GNU/Linux 7.0, Belenos

Configured using:
 `configure 'CFLAGS=-g -O0''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GCONF GSETTINGS NOTIFY
LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK2 X11

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: RMAIL

Minor modes in effect:
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Type C-x 1 to delete the help window.
Char: · (183, #o267, #xb7, file ...) point=1490 of 2018 (74%) column=20

Char: ꟾ (43006, #o123776, #xa7fe, file ...) point=1489 of 2018 (74%) column=19
Quit
R is undefined
Quit
save-excursion: Search failed: "[[]TRUNCATED .*] "
Mark set

Load-path shadows:
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Memory information:
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 (heap 1024 22934 1223))
[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]


-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

bug#21363: 25.0.50; Some characters confuse display

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Date: Thu, 27 Aug 2015 12:28:37 -0400
> 
> This text from a message to emacs-devel
> 
>    AVGVSTÓ·SACR·
>    A·A·LV́CIꟾ·A·FꟾLIꟾ·MEN·
>    PROCVLVS·ET·IV́LIÁNVS·
>    P · S ·
>    DÉDICÁTIÓNE·DECVRIÓNIBVS·ET·
>    AVGVSTÁLIBVS·CÉNAM·DEDÉRVNT
> 
> confuses display on my Linux console.
> If you go to the second line of the text and type C-e,
> the cursor appears on the final middledot.
> 
> I've seen other strange things happen just moving around on that text,
> such as displaying lines in the wrong place, but I can't
> reproduce them.

Do the problems go away if you turn off auto-composition-mode?

bug#21363: 25.0.50; Some characters confuse display

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > Do the problems go away if you turn off auto-composition-mode?

Yes, they do.  The bug seems limited to when Auto-Composition mode is enabled.


-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

bug#21363: 25.0.50; Some characters confuse display

[Lars Ingebrigtsen]

Richard Stallman <rms@gnu.org> writes:

> This text from a message to emacs-devel
>
>    AVGVSTÓ·SACR·
>    A·A·LV́CIꟾ·A·FꟾLIꟾ·MEN·
>    PROCVLVS·ET·IV́LIÁNVS·
>    P · S ·
>    DÉDICÁTIÓNE·DECVRIÓNIBVS·ET·
>    AVGVSTÁLIBVS·CÉNAM·DEDÉRVNT
>
> confuses display on my Linux console.
> If you go to the second line of the text and type C-e,
> the cursor appears on the final middledot.

I can reproduce this problem in Emacs 28 (on the Linux console).

Switching `auto-composition-mode' indeed fixes the problem, so perhaps
we should just do that automatically when running on the console?  Let's
see...  is that the lisp/term/linux.el file?

Let's see...  Yes, putting

  ;; Compositions confuse cursor movement.
  (global-auto-composition-mode -1)

into that file fixes the issue for me on the Linux console, and does not
seem to be triggered when running from a terminal, so I'll go ahead and
push that change.

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

bug#21363: 25.0.50; Some characters confuse display

[Andreas Schwab]

On Aug 16 2021, Lars Ingebrigtsen wrote:

> Switching `auto-composition-mode' indeed fixes the problem, so perhaps
> we should just do that automatically when running on the console?  Let's
> see...  is that the lisp/term/linux.el file?
>
> Let's see...  Yes, putting
>
>   ;; Compositions confuse cursor movement.
>   (global-auto-composition-mode -1)
>
> into that file fixes the issue for me on the Linux console, and does not
> seem to be triggered when running from a terminal, so I'll go ahead and
> push that change.

I think auto-composition-mode should only be disabled on this terminal.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

bug#21363: 25.0.50; Some characters confuse display

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Mon, 16 Aug 2021 14:48:32 +0200
> Cc: 21363@debbugs.gnu.org
> 
> Switching `auto-composition-mode' indeed fixes the problem, so perhaps
> we should just do that automatically when running on the console?  Let's
> see...  is that the lisp/term/linux.el file?
> 
> Let's see...  Yes, putting
> 
>   ;; Compositions confuse cursor movement.
>   (global-auto-composition-mode -1)
> 
> into that file fixes the issue for me on the Linux console, and does not
> seem to be triggered when running from a terminal, so I'll go ahead and
> push that change.

I think we should only do that if this happens to everyone.  Can more
people please try this recipe and report back?

bug#21363: 25.0.50; Some characters confuse display

[Lars Ingebrigtsen]

Andreas Schwab <schwab@linux-m68k.org> writes:

> I think auto-composition-mode should only be disabled on this terminal.

Makes sense.  So would calling `(auto-composition-mode -1)' instead here
to the trick?  (I'm slightly vague on the evaluation order of the term
files...)

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

bug#21363: 25.0.50; Some characters confuse display

[Andreas Schwab]

On Aug 16 2021, Lars Ingebrigtsen wrote:

> Andreas Schwab <schwab@linux-m68k.org> writes:
>
>> I think auto-composition-mode should only be disabled on this terminal.
>
> Makes sense.  So would calling `(auto-composition-mode -1)' instead here
> to the trick?  (I'm slightly vague on the evaluation order of the term
> files...)

Since auto-composition-mode is a automatic buffer-local variable, that
won't work, it would have to be made terminal-local.  Unfortunately, you
can't have both.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

bug#21363: 25.0.50; Some characters confuse display

[Lars Ingebrigtsen]

Andreas Schwab <schwab@linux-m68k.org> writes:

>> Makes sense.  So would calling `(auto-composition-mode -1)' instead here
>> to the trick?  (I'm slightly vague on the evaluation order of the term
>> files...)
>
> Since auto-composition-mode is a automatic buffer-local variable, that
> won't work, it would have to be made terminal-local.  Unfortunately, you
> can't have both.

We have terminal-local variables!?

So I guess we'll have to introduce a predicate for
`global-auto-composition-mode' that would allow us to turn on
auto-composition-mode only in buffers on certain terminals, I guess.

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

bug#21363: 25.0.50; Some characters confuse display

[Stephen Berman]

On Mon, 16 Aug 2021 16:16:06 +0300 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Lars Ingebrigtsen <larsi@gnus.org>
>> Date: Mon, 16 Aug 2021 14:48:32 +0200
>> Cc: 21363@debbugs.gnu.org
>>
>> Switching `auto-composition-mode' indeed fixes the problem, so perhaps
>> we should just do that automatically when running on the console?  Let's
>> see...  is that the lisp/term/linux.el file?
>>
>> Let's see...  Yes, putting
>>
>>   ;; Compositions confuse cursor movement.
>>   (global-auto-composition-mode -1)
>>
>> into that file fixes the issue for me on the Linux console, and does not
>> seem to be triggered when running from a terminal, so I'll go ahead and
>> push that change.
>
> I think we should only do that if this happens to everyone.  Can more
> people please try this recipe and report back?

I can reproduce the problem on the Linux console and the proposed fix
works for me: after disabling global-auto-composition-mode and then
visiting the file containing that text, the problem is gone.  (If I
first visit the file and then disable global-auto-composition-mode (or
just auto-composition-mode), I have to switch the buffer off the window
and then back to it in order to get the correct display.)

Steve Berman