bug#17497: 24.4.50; TTY menu glitches

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 03 Jun 2014 18:21:55 -0400
> From: Thomas Dickey <dickey@his.com>
> Cc: dickey@his.com, monnier@iro.umontreal.ca, 17497@debbugs.gnu.org
> 
> > All this, including input interfering with output, happens during
> > normal Emacs redisplay, but we have never heard any complaints about
> > corrupted display like the ones we get with the menus.
> 
> The menus cover _half_ of the screen, defeating any attempt to speed up
> scrolling by using the terminal's indexing/scrolling features.  In the
> view without menus, the scrolled text (unless you're considering scrolling
> a pane of a vertically split window), is full-width, and works with
> the terminal's scrolling features.

You can easily make the "normal" display do the same: just divide the
window in 2 halves by typing "C-x 3", then scroll one of them with
C-v or the arrow keys.  If you actually lean on the scrolling key, you
will make sure output and input are intermingled.

If this situation were inherently conducive to display bugs, we would
have heard about it long time ago.

So I think there's something about the screen update due to menus that
triggers these problems.  I just have run out of ideas about what that
factor(s) could be, and I don't have access to any system where this
happens to debug that.