Re: [csswg-drafts] [css-fonts] Font Sizing for Accessibility (#6709)

## A TL;DR Summary:

- ` font-size: ` is not a "best way" to set a font size.
    - The ultimate results on screen will vary depending on the font family.
    - It is impossible to change the behavior of  ` font-size: ` due to existing usage of course.
- ` font-x-size: ` for setting font based on x-height is intended as a **_REPLACEMENT_** for ` font-size: `
    - It will allow better control of how latin and similar fonts render on screen.
    - The companion ` font-cap-size: ` gives more direct control of upper case rendered size.
    - ` font-abs-size: ` as a companion for other languages with no case, to provide control of the absolute rendered size.
- ` ex-to-em ` is a companion to provide affirmative control of the em unit when ` font-x-size: ` type properties are in use.

Other critical metrics for readability are font weight, leading (line-height), tracking (letter-spacing), and kerning. There is no effective standard how size nor any of these result in a particular family rendering to screen.

These are among the most critical accessibility failures facing web content today.
_(Along with the mistaken belief that "4.5:1" is adequate contrast for body text, which it is not.)_


Thank you,

Andy


PS: Here's a chart that outlines critical reading size, based on visual angle, which references the research of Dr. Lovie-Kitchin on critical size for readability. As a statistical reference, only about 45% of the population is at or better than 20/20. "Impairments begin at 20/20" you might say. The average and median acuity is about 20/40 (which is the limit in all 50 states for a non-commercial drivers license). "Low vision" is 20/70 and worse, and "blind" is 20/200 and worse.

<img width="1317" alt="image" src="https://user-images.githubusercontent.com/42009457/136382318-bdaaf593-b5a0-4d78-99f5-db254a8e479f.png">




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Received on Thursday, 7 October 2021 12:25:13 UTC