Subject: 30.0.50; set-face-attribute can not set the medium weight of IBM Plex Mono on Windows 10

From: Eason Huang <[email-masked]>
Date: Sat, 22 Jul 2023 09:23:28 +0800

Hi Emacs,

I tried to use the medium weight of IBM Plex Mono font on Windows 10,
and find that `set-face-attribute` can not make it works as expectd.

Steps to reproduce:

1. Download IBM Plex Mono font by this link:
https://github.com/IBM/plex/releases/download/v6.3.0/TrueType.zip
2. Unzip the TrueType.zip and install the IBM Plex Mono
3. Start Emacs with `emacs -Q`
4. In the `*scratch*` buffer, eval the code below:
```
(set-face-attribute 'default nil :font (format
"%s:pixelsize=%d:weight=medium" "IBM Plex Mono" 20))

```
5. `M-x describe-char`, will get info about font as below:
 harfbuzz:-outline-IBM Plex Mono-regular-normal-normal-mono-20-*-*-*-c-*-iso8859-1 (#x03)

And you can see the regular weight is used instead.

expectd: return the medium weight of font.

The workaround recently I used:

```
(set-face-attribute 'default nil :font (format
"%s:pixelsize=%d:weight=medium" "IBM Plex Mono Medm" 20))
```
`M-x describe-char`, will get info about font as below:
harfbuzz:-outline-IBM Plex Mono Medm-medium-normal-normal-mono-20-*-*-*-c-*-iso8859-1 (#x18)

But use the `IBM Plex Mono Medm` name is not convenient for me, because
I also want to switch to other weights sometimes, such as:

```
(set-face-attribute 'default nil :font (format "%s:pixelsize=%d:weight=regular" "IBM Plex Mono" 20))
(set-face-attribute 'default nil :font (format "%s:pixelsize=%d:weight=bold" "IBM Plex Mono" 20))
```
It would be more consistent If we can use the `IBM Plex Mono` font name
with all font weights.

Meanwhile, I aslo tested `set-face-attribute` on macOS, it works as expected with
the same font setting.

If you need more information, please let me known.

-- 
Best regard, Eason Huang

GNU Emacs 30.0.50 (build 1, x86_64-w64-mingw32, git sha1 207cd4c2357) of
2023-07-17

Windowing system distributor 'Microsoft Corp.', version 10.0.19045
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