Bug#847479: xterm: display issue with double-width character like ? on the last column via ncurses

[Vincent Lefevre]

On 2017-05-07 16:30:24 -0400, Thomas Dickey wrote:
> a typescript (from "script") helps.

After trying again. the problem seems to occur only when one resizes
the terminal window. So, a typescript doesn't help. It seems to be a
problem similar to what I had already reported under other conditions:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=738794

The problem disappears if the xterm window is redrawn, e.g. via the
RefreshWindow fvwm command:

  RefreshWindow
Causes the chosen window to redraw itself.  All pending updates
of the window's style and look are applied immediately.  E.g. if
Style or TitleStyle commands were issued inside a fvwm function.

To reproduce the bug, use xterm with the 7x13 font.

Consider the following mbox file:

--
>From a@b.invalid Thu Dec  8 16:50:47 2016
Subject: =?utf-8?Q?character_like_?= =?utf-8?B?8J+NuA==?= on

--

Open it with:

  mutt -F /dev/null -R -f test.mbox

Then reduce the xterm window width so that the second column of the
double-width character is removed (but not the first column).

For instance, you should get initially:

q:Quit  d:Del  u:Undel  s:Save  m:Mail  r:Reply  g:Group  ?:Help  
   1 N   Dec 08 a@b.invalid (  0K) character like XY on   

where "XY" is the double-width character (here it appears as a
wide question mark in a circle since the character isn't probably
in the font). So, reduce the xterm window width so that the first
line is:

q:Quit  d:Del  u:Undel  s:Save  m:Mail  r:Reply  g:Grou

Here, the second line is:

   1 N   Dec 08 a@b.invalid (  0K) character like

but some pixels on the right of the last column are visible
(a bit like in bug 738794 mentioned above).

-- 
Vincent Lefèvre  - Web: 
100% accessible validated (X)HTML - Blog: 
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

Bug#847479: xterm: display issue with double-width character like ? on the last column via ncurses

[Thomas Dickey]

- Original Message -
| From: "Vincent Lefevre" <vinc...@vinc17.net>
| To: dic...@his.com, 847...@bugs.debian.org
| Sent: Sunday, May 7, 2017 12:56:32 PM
| Subject: Bug#847479: xterm: display issue with double-width character like ? 
on the last column via ncurses
| 
| On 2017-05-07 10:53:24 -0400, Thomas Dickey wrote:
| > Attaching a script, for discussion.  I don't see the problem, but
| > noticed
| > that the character is "new", and for instance if you were running
| > xterm
| > remotely so that the wcwidth wasn't known then you could get odd
| > results.
| 
| I can't reproduce the problem with your script. But it is
| reproducible
| with Mutt. Maybe a problem that occurs only when margins are used.
| I don't know what ncurses does exactly...
| 
| Everything is local on the machine.


a typescript (from "script") helps.

-- 
Thomas E. Dickey <dic...@invisible-island.net>
http://invisible-island.net
ftp://invisible-island.net

Bug#847479: xterm: display issue with double-width character like ? on the last column via ncurses

[Vincent Lefevre]

On 2017-05-07 10:53:24 -0400, Thomas Dickey wrote:
> Attaching a script, for discussion.  I don't see the problem, but noticed
> that the character is "new", and for instance if you were running xterm
> remotely so that the wcwidth wasn't known then you could get odd results.

I can't reproduce the problem with your script. But it is reproducible
with Mutt. Maybe a problem that occurs only when margins are used.
I don't know what ncurses does exactly...

Everything is local on the machine.

-- 
Vincent Lefèvre  - Web: 
100% accessible validated (X)HTML - Blog: 
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

Bug#847479: xterm: display issue with double-width character like ? on the last column via ncurses

[Thomas Dickey]

On Thu, Dec 08, 2016 at 05:37:15PM +0100, Vincent Lefevre wrote:
> Notes:
> 
> The character appears in the subject of this mail, so that you can
> use it as a test case. :)
> 
> The problem doesn't appear with a shell and printf. Thus I assume that
> it may be related to margins and things like that.

Attaching a script, for discussion.  I don't see the problem, but noticed
that the character is "new", and for instance if you were running xterm
remotely so that the wcwidth wasn't known then you could get odd results.

-- 
Thomas E. Dickey 
http://invisible-island.net
ftp://invisible-island.net
#!/usr/bin/env perl

use strict;
use warnings;
use Encode 'encode_utf8';

binmode( STDOUT, ":utf8" );

my $margin = `tput cols`;
my $length = $margin - 8;
for my $n ( 1 .. 10 ) {
for my $m ( 1 .. $length ) {
printf '.';
}
printf "{{%s}}\n", chr(0x1f378);
$length++;
}
printf 'DONE!\n'


signature.asc
Description: Digital signature

Bug#847479: xterm: display issue with double-width character like  on the last column via ncurses

[Vincent Lefevre]

Notes:

The character appears in the subject of this mail, so that you can
use it as a test case. :)

The problem doesn't appear with a shell and printf. Thus I assume that
it may be related to margins and things like that.

-- 
Vincent Lefèvre  - Web: 
100% accessible validated (X)HTML - Blog: 
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

Bug#847479: xterm: display issue with double-width character like  on the last column via ncurses

[Vincent Lefevre]

Package: xterm
Version: 327-1
Severity: minor

In Mutt, when a double-width character from the subject appears on the
last column (in the Mutt index menu), then the left part of the second
half of the character is visible. Something like that.

For instance, if the character rendering would be denoted by:

  12345678

where 1234 would correspond to the last column and 5678 would
correspond to the next column, where only the pixels in 5 would
be visible before the right edge of the xterm window, then what
is visible seems to be the pixels from 5.

Said otherwise, the behavior is like if xterm would render the
character in its window (thus the 12345 part) then cleared the
last column (1234).

This is very similar to bug 844325.

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'stable-updates'), (500, 
'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.8.0-2-amd64 (SMP w/12 CPU cores)
Locale: LANG=POSIX, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages xterm depends on:
ii  libc6   2.24-8
ii  libfontconfig1  2.11.0-6.7
ii  libice6 2:1.0.9-1+b1
ii  libtinfo5   6.0+20161126-1
ii  libutempter01.1.6-3
ii  libx11-62:1.6.4-2
ii  libxaw7 2:1.0.13-1
ii  libxft2 2.3.2-1
ii  libxinerama12:1.1.3-1+b1
ii  libxmu6 2:1.1.2-2
ii  libxpm4 1:3.5.11-1+b1
ii  libxt6  1:1.1.5-1
ii  xbitmaps1.1.1-2

Versions of packages xterm recommends:
ii  x11-utils  7.7+3

Versions of packages xterm suggests:
pn  xfonts-cyrillic  

-- no debconf information