bug#64780: 30.0.50; set-face-attribute can not set the medium weight of IBM Plex Mono on Windows 10

[Eason Huang]

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
System Description: Microsoft Windows 10 Pro (v10.0.2009.19045.3208)

Configured using:
 'configure --without-native-compilation --without-dbus'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NOTIFY
W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XPM ZLIB

Important settings:
  value of $LANG: CHS
  locale-coding-system: cp936

Major mode: Lisp Interaction

Minor modes in effect:
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  global-eldoc-mode: t
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  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
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Load-path shadows:
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Memory information:
((conses 16 74158 21444) (symbols 48 20879 3) (strings 32 82668 1435)
 (string-bytes 1 1859302) (vectors 16 14862)
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