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

[Gregory Heytings]

> > This is because 'write' deliberatly leaves the bottom-right corner 
> > alone if the terminal has "auto right margin" (autowrap).
>
> But AFAIU, the bug actually shows that we somehow _do_ write there, 
> although the display engine assumes we don't.  Right?

Yes, that's what the bug shows.  We do (sometimes) write something there, 
and we shouldn't.  (And if the feature request in bug#57607 is 
implemented, we should write something there, but always.)