bug#57728: 29.0.50; Emacs writes wrong glyph at the bottom-right corner of text terminals

[Akib Azmain Turja]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Lars Ingebrigtsen <larsi@gnus.org>
>> Cc: akib@disroot.org,  57728@debbugs.gnu.org
>> Date: Sun, 11 Sep 2022 20:18:03 +0200
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> > Doesn't happen here, neither on MS-Windows nor on GNU/Linux to which I
>> > SSH-login via PuTTY (which AFAIK emulates xterm).  I guess this really
>> > is specific to some terminals.
>> 
>> My example was with gnome-terminal on the current Ubuntu, for what it's
>> worth.
>
> Someone with access to that terminal will have to debug this.

I can reproduce on XTerm and Linux console, I hope you have access to
those.

>
> My guess is that something we do when we rewrite the lines while
> scrolling the display erases those glyphs by side effect, but Emacs
> doesn't know that.  Since all the lines have the continuation glyph,
> it makes sense for Emacs to rewrite only the part of each line up to
> and excluding the continuation glyphs, relying on them to remain on
> the glass.

Yeah, tty_write_glyphs and tty_write_glyphs_with_face in term.c does the
magic, it doesn't dare to write to that (bottom-right corner) position.

-- 
Akib Azmain Turja

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