bug#49622: 27.2; A new MacOS display heisenbug

[Eli Zaretskii]

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> From: Devon Sean McCullough <Devon2020@jovi.net>
> Date: Sun, 25 Jul 2021 14:01:38 -0400
> 
> On 2021-07-18 15:00, Eli Zaretskii wrote:
> 
> > Which font is used here?  Is it the same font in the "good" and the
> > "bad" display?
> 
> Emacs 27 and 28 with -Q both report the same font for this character
> and after many trials, both manifest the bug more often than not.

My first suspicion is that this has something to do with your video
driver.

>               Peace
>                       --Devon
> 
> P.S.  In a "CLEAN" Emacs, C-u C-x =
> 
>               position: 153 of 177 (86%), column: 7
>              character: ⟡ (displayed as ⟡) (codepoint 10209, #o23741, #x27e1)
>                charset: unicode (Unicode (ISO10646))
> code point in charset: 0x27E1
>                 script: symbol
>                 syntax: w     which means: word
>               category: .:Base
>               to input: type "C-x 8 RET 27e1" or "C-x 8 RET WHITE 
> CONCAVE-SIDED DIAMOND"
>            buffer code: #xE2 #x9F #xA1
>              file code: #xE2 #x9F #xA1 (encoded by coding system utf-8-unix)
>                display: by this font (glyph code)
>      mac-ct:-*-PCMyungjo-normal-normal-normal-*-12-*-*-*-m-0-iso10646-1 
> (#x26F9)
> 
> Character code properties: customize what to show
>    name: WHITE CONCAVE-SIDED DIAMOND
>    general-category: Sm (Symbol, Math)
>    decomposition: (10209) ('⟡')
> 
> There are text properties here:
>    face                 font-lock-comment-face
>    fontified            t

Since you see just a box, it means this font doesn't support that
character.  So I wonder why this font is used for that character.  Did
you try to install Symbola?

> P.P.S. I added a new screen shot at http://jovi.net/Emacs-Bug/Render
> 
> > And why do you say this is a "new" bug? new as compared to when?
> New to me anyway — my searches turned up no similar bug reports.

New to you because you never saw it before, or new because previous
version(s) didn't have it?