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Say I create a fontset and populate it with fonts:

(create-fontset-from-fontset-spec (font-xlfd-name (font-spec :registry "fontset-mine"))) (set-fontset-font "fontset-mine" 'latin "Noto Serif") (set-fontset-font "fontset-mine" 'kana "Noto Serif CJK JP")

I can't find a way to get a face to use this fontset. For example, if I set it like (set-face-attribute 'my-test-face nil :font "fontset-mine"), then my-test-face will show kana scripts in Noto Sans CJK KR, not JP (presumably a fallback specified by fontset-standard or something).

According to investigations by Yuan Fu, when set-face-attribute or similar is given a fontset as :font, it merely extracts the ASCII font of that set and copies its family, height, etc. onto the face (corroborated by a comparison of describe-face before and after set-face-attribute). This means I can't use it to set more than one font to a face simultaneously; anything not supported by the one font that is set, will use some Emacs-wide fallback. The bug report talks about setting the :fontset attribute, but that doesn't seem to do anything either. (EDIT: this last statement was wrong; see the answer.)

So my question is: is there a way to apply user-defined fontsets to any faces? By user-defined, I mean those created in init.el with create-fontset-from-fontset-spec, as opposed to built-in ones like fontset-standard. If not, are user-defined fontsets useful for anything?

My particular use case is as follows. I want to switch between these sets of fonts, depending on the type of document I'm editing.

  • ETbb for latin, Noto Serif CJK JP for kana.
  • Noto Sans for latin, Noto Sans CJK JP for kana.

(There are lots more scripts I'm interested in, but I'll focus on two.) Right now I can produce a face that has any of the following, none of which is what I want.

  • ETbb for latin and some fallback font for kana
  • Noto Sans for latin and some fallback font for kana
  • Some fallback font for latin and Noto Serif CJK JP for kana
  • Some fallback font for latin and Noto Sans CJK JP for kana

The point is, without a way to apply a fontset as one indivisible unit, I can only control latin or kana, not both; one of them will get specified by default, not by me.

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  • What does describe-fontset show you for your new fontset? Commented Jan 31, 2022 at 13:55
  • @db48x It shows C-@ .. DEL -*-Noto Serif-*-*-*-*-*-*-*-*-*-*-*-* for ASCII and ぀ .. ヿ (#x3040 .. #x30FF) -*-Noto Serif CJK JP-*-*-*-*-*-*-*-*-*-*-*-* for Japanese, so set-fontset-font is working as it should, AFAICT. (FYI, a sample kana is あ at #x3042) Commented Jan 31, 2022 at 15:01
  • I'm not very familiar with this stuff. But did you try set-face-font? It sets attribute :font, whose value can be a font or a fontset. Commented Jan 31, 2022 at 16:04
  • I think the doc in the Elisp manual isn't obvious enough about the value of :font being able to be a fontset. But that seems to be what lets a face have different fonts for different chars. I filed Emacs bug #53664 to improve this aspect of the manual. Commented Jan 31, 2022 at 16:08
  • @Drew Thanks, I hadn't considered set-face-font. Unfortunately, it's the same deal as setting :font with set-face-attribute. The doc is wrong in this respect. Commented Feb 1, 2022 at 3:11

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Yikes. I had a fresh look at this after a good night's sleep, and it turns out I was wrong to say that setting the :fontset attribute doesn't work. My test code had a critical typo, and I also tried custom-theme-set-faces etc. in addition to set-face-attribute, and then mixed things up. Sorry for the confusion.

To set the record straight:

  • You can apply a fontset to a face by setting its :fontset attribute with set-face-attribute. The face will then use all fonts in the set as expected. EDIT: the values of :font, :family etc. override :fontset, so if you're modifying a pre-existing face like variable-pitch, be sure to adjust those other attributes as well.
  • However, you cannot set the :fontset attribute using custom-theme-set-faces or defface, which ignore that attribute.
  • The manual currently says in some places that you can pass in a fontset for the :font attribute or the font argument of set-face-font, but this is misleading at best: the fontset will be stripped of the "set" part and be treated as just an ASCII font.

I think the second bullet means that there's no way to enable/disable fontsets with themes, but someone more knowledgeable on themes will have to set me straight on this.

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  • You can accept your own answer, BTW. Commented Feb 1, 2022 at 16:19

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