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

[Vincent Lefevre <vincent@vinc17.net>]

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 <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)