bug#71866: 30.0.50; [macOS] Cursor hiding char behind it with certain theme customization

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 24 Jul 2024 17:34:18 +0300
> Cc: alan@idiocy.org, 71866@debbugs.gnu.org
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> > Then I don't understand what you mean by "many/most characters become
> > blank under cursor".  It seems to contradict what you say now: that
> > "only one char is blanked".
> 
> In the recipe I managed to produce starting with 'emacs -Q', only 's' is 
> such a character (see the original description). When point is over 'a' 
> or 'd', no bug.
> 
> In actual practice, many/all characters exhibit the problem, I just 
> haven't managed to create a simple repro for this.

Curiouser and curiouser.  And when you say that 's' is a character
that is blanked, does it mean that if you have several such
characters, then moving the cursor to any of them will show the
problem?

I don't understand even in principle how a display problem could be
specific to some characters, unless it's something related very
strongly to the font that is being used.  So what happens in a session
in which 's' is a problematic character if you put a face property on
's' that forces Emacs to use a different font?