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

[Dmitry Gutov <dmitry@gutov.dev>]

On 24/07/2024 19:29, Eli Zaretskii wrote:
>> 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?

Yes: with buffer contents 'asdasdasdasd' (or any small variations of 
that), only the 's' chars exhibit the problem with the repro script.

With my custom init, all of the chars exhibit 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?

I tried something different: enabled variable-pitch-mode.

* With the small repro script in the first message, the problem is gone.

* With my custom init, the problem remains for all chars. *shrug*