bug#41645: 27.0.91; Combining Grapheme Joiner (#x34f) gui artifacts

[Eli Zaretskii]

> Date: Mon, 1 Jun 2020 14:45:15 +0100
> From: David Fussner via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> After emacs -Q, open a unicode text file and type a few letters, then
> the Combining Grapheme Joiner (C-x 8 RET 34f), then a few more
> letters. Press and hold the left arrow key to go back across the CGJ and
> here it leaves behind a second box cursor while the actual cursor
> continues to move across the text beyond. If you input multiple CGJs
> you'll get multiple box cursors scattered wherever you put them,
> assuming you don't change to the right arrow and hold that down, which
> removes the artifacts as it goes along. (See attached image, with 3
> artifacts in a line and the actual cursor off to the left.)

I cannot reproduce this on my system, FWIW.  Very strange.