bug#58184: Faulty font selection for Latin characters

Here are the steps to reproduce:

1. emacs -Q

2. enter these three words:

hṛṣyatha (h#x1E5B#x1E63yatha)
kṣiptaḥ (k#x1E63ipta#x1E25)
viśāmaḥ (vi#x015B#x0101ma#x1E25)

At this stage everything is fine, all of the characters use the same font therefore all of them return the same font after evaluating (font-at (point)) on them:

#<font-object "-ADBO-Source Code Pro-regular-normal-normal-*-32-*-*-*-m-0-iso10646-1">

3. Now eval the following in the buffer

(set-face-attribute 'default nil
:font "JetBrains Mono"
:weight 'regular
:height 170)

Now you'll notice that the font for some of the characters above are different from JetBrainsMono, these characters are:

ṛ (#x1e5b)

ṣ (#x1e63)

ḥ (#x1e25)

(font-at (point)) returns #<font-object "-UKWN-Latin Modern Mono-regular-normal-normal-*-57-*-*-*-*-0-iso10646-1"> on all of them

while for the rest of the characters gives #<font-object "-JB-JetBrains Mono-regular-normal-normal-*-57-*-*-*-m-0-iso10646-1">

Changing the weight from regular to medium also does not help, the offending characters instead of being displayed with Latin Modern Mono are

now displayed with: #<font-object "-GOOG-Noto Serif Display-medium-normal-normal-*-57-*-*-*-*-0-iso10646-1">

while the rest of the characters are displayed with #<font-object "-JB-JetBrains Mono-medium-normal-normal-*-57-*-*-*-m-0-iso10646-1">

I have also included screenshots from emacs -Q before, emacs -Q after and hb-view from JetBrains

Hope this makes things clear, if something is still missing please tell me.

Thanks

On Fri, Sep 30, 2022 at 11:33 AM Eli Zaretskii <eliz@gnu.org> wrote:

> From: समीर सिंह Sameer Singh
> <lumarzeli30@gmail.com>
> Date: Fri, 30 Sep 2022 04:49:37 +0530
>
> codepoints of faulty characters in the above mail:
> ṣ #x1e63
> ṇ #x1e47
> ḍ #x1e0d

Please _always_ show the actual text, not just an image of its
display. It is practically impossible to know what text you used
given just its display screenshot, especially when character
compositions are involved.

In any case, we will need a reproducible recipe starting from
"emacs -Q". Also, please include in your report the output of

M-: (font-at (point)) RET

for the "good" and the "faulty" characters.

In general, reporting issues with fonts need as many specific details
as you can collect, because these issues are inherently
system-specific, due to different sets of fonts installed on each
system, and due to font customizations that are outside of Emacs (on
the Fontconfig level). The probability of getting unreproducible
results is very high, and each detail helps.

From:	समीर सिंह Sameer Singh
Subject:	bug#58184: Faulty font selection for Latin characters
Date:	Fri, 30 Sep 2022 16:53:01 +0530