bug#50564: 28.0.50; Display artifacting in package list

[Eli Zaretskii]

> Date: Mon, 13 Sep 2021 16:49:01 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> 
> If you move to the end of a truncated line in the package list, part of
> the previous screen will be retained when it should actually be
> invisible.
> 
> To reproduce this problem, start emacs -Q, select the entry "news" from
> the package finder (the command finder-by-keyword), then turn on
> truncate-lines (if it is not already on) in the package list containing
> results from the finder, resize the window showing the package list so
> that lines are being truncated, and move to the end of a truncated line.
> 
> This problem is not present in Emacs 27.2, and cannot be reproduced on a
> TTY frame.
> 
> Parts of the previous content of the display will be preserved, which go
> away upon invoking redraw-display.

I don't think I can reproduce this here, at least not in "emacs -Q".
But it's hard to say because you didn't tell which part(s) of the
previous contents I should watch, and there's a lot of stuff on the
screen to be sure that none of it was left behind.

So please describe the recipe in more detail:

  . to what width to resize the frame
  . how do you "move to the end of a truncated line"
  . which parts of the display are left on the screen

Thanks.