Re: [csswg-drafts] [css-fonts] Proposal to extend CSS font-optical-sizing (#4430)

The OT spec [definition of opsz](https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_opsz) makes no mention of CSS, but CSS and other implementors must base their opsz unit scale on *something*, and that’s what we’re trying to clarify, and offer control of, here for CSS. That something in current shipping browsers is two 1:1 mappings:

* opsz = font-size in px for screen media
* opsz = font-size in pt for print media

Thus text in a fixed font-size set in a font with an opsz axis *uses different glyph shapes on screen and in print*. Having the option to fix the browser to one of these scales, so as to guarantee identical glyph shapes for screen and print, seems to be a reasonable desire. Not default, but something that a CSS author should have available to them.

BTW nothing in the proposal prevents a future or special-purpose user agent (such as a browser optimized for accessibility) having a completely different default from Safari. In fact the proposal provides a flexible model for defining defaults.

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Received on Thursday, 13 May 2021 17:47:25 UTC