Re: [csswg-drafts] [css-fonts-4] Which type of font family names are system font names? (#9292)

It is new, because the `font-family` property defines three tokens and allows two of them; it seemed necessary to say why the third one was there. 

The older text from which one might infer this is [still there](https://drafts.csswg.org/css-fonts-4/#font-prop):

> System fonts can only be set as a whole; that is, the font family, size, weight, style, etc. are all set at the same time. These values can then be altered individually if desired. If no font with the indicated characteristics exists on a given platform, the user agent should either intelligently substitute (e.g., a smaller version of the [caption](https://drafts.csswg.org/css-fonts-4/#valdef-font-caption) font might be used for the [small-caption](https://drafts.csswg.org/css-fonts-4/#valdef-font-small-caption) font), or substitute a user agent default font. As for regular fonts, if, for a system font, any of the individual properties are not part of the operating system’s available user preferences, those properties should be set to their initial values.

> That is why this property is "almost" a shorthand property: system fonts can only be specified with this property, not with [font-family](https://drafts.csswg.org/css-fonts-4/#propdef-font-family) itself, so [font](https://drafts.csswg.org/css-fonts-4/#propdef-font) allows authors to do more than the sum of its subproperties. However, the individual properties such as [font-weight](https://drafts.csswg.org/css-fonts-4/#propdef-font-weight) are still given values taken from the system font, which can be independently varied.

> Note that the keywords used for the system fonts listed above are only treated as keywords when they occur in the initial position, in other positions the same string is treated as part of the font family name:

Although the grammar of the `font` shorthand now uses the  `<system-family-name>` token rather than inlining a list of names.

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Received on Thursday, 5 October 2023 13:28:45 UTC