Bug#1122519: xterm: display corruption with double-width characters

[Vincent Lefevre <vincent@vinc17.net>]

On 2025-12-17 01:34:03 +0100, Vincent Lefevre wrote:
> To reproduce the issue more easily, I've attached Xterm.log.xz
> (compressed xterm log file obtained with the simple test on
> xterm-bug.mbox). Just run
> 
>   xterm -geometry 80x60 -e 'unxz -c Xterm.log.xz ; sleep 999'
> 
> See the differences between xterm-403.png and xterm-405.png (attached).

In the log file, there is the following sequence of characters:

  🧝🏻‍♂️🌋 Candlelight

U+1F9DD ELF
U+1F3FB EMOJI MODIFIER FITZPATRICK TYPE-1-2
U+200D ZERO WIDTH JOINER
U+2642 MALE SIGN
U+FE0F VARIATION SELECTOR-16
U+1F30B VOLCANO
U+0020 SPACE
U+0043 LATIN CAPITAL LETTER C
etc.

With xterm 403, I get:

U+1F9DD ELF
U+1F3FB EMOJI MODIFIER FITZPATRICK TYPE-1-2
U+2642 MALE SIGN
U+FE0F VARIATION SELECTOR-16
U+1F30B VOLCANO
U+0020 SPACE
U+0043 LATIN CAPITAL LETTER C
etc.

but with xterm 405, I get:

U+1F9DD ELF
U+1F3FB EMOJI MODIFIER FITZPATRICK TYPE-1-2
U+2642 MALE SIGN
U+FE0F VARIATION SELECTOR-16
U+0020 SPACE
U+1F30B VOLCANO
U+0020 SPACE
U+0043 LATIN CAPITAL LETTER C
etc.

i.e. there is an additional space after U+FE0F VARIATION SELECTOR-16.

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