Re: [csswg-drafts] [css-env][css-values] UAs inconsistent in how OS font settings affect the default font-size `medium` (#10674)

I just learned about this discussion. It touches on something I’ve felt was lacking for many years: nomenclature (and perhaps identity and/or formalisation) for what the `em` and `rem` units mean on `:root` `font-size` and in media queries. Personally I’ve been calling it “browser em” for quite a few years, am unaware of anyone else concretely naming the concept, and have written at least documentation with this unofficial unit, `bem`. (Pity about the naming conflict with the Block-Element-Modifier methodology.)

Am I correct in thinking:

1. That this isn’t defining a new concept, just giving a name for an ancient concept, and allowing it to be used in more places (via this new unit and `env()` variable).
2. That under this proposal, use of the `em` and `rem` units on the root element’s `font-size`, and in media queries, would now be synonymous with `pem`.
3. That this also means the `pem` could vary by document language. (Again, this is part of existing implementations. In Firefox, you can control it by language; bypassing the UI, set pref `font.size.variable.ar` to 10, and `data:text/html,<html lang=ar>…` will have a base font size of 10.)

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Received on Sunday, 2 March 2025 15:42:37 UTC