Re: [csswg-drafts] [mediaqueries-5] prefers-contrast: high media feature does not accurately describe the macOS/iOS state (#2943)

To recap, I think there are several distinct concepts of contrast preference:

- *True high contrast*, along the lines of the Windows High Contrast Mode. This is often a light-on-dark colour scheme with white or yellow text, black background, reduced detail, few gradations of colour etc. This is intended for users with unusual vision impairments, who may also use other accommodations such as screen magnification to be able to access content.
   - Despite typically being light-on-dark, this is quite different from a "night mode" theme.
   - This is often an operating system setting which affects how text, borders and images are displayed. In this case, developers may wish to make adjustments to ensure that these modifications don't create other problems. This is the "forced" case, I think.
  - However, certain apps also provide [high contrast themes](https://blog.jetbrains.com/idea/2018/10/intellij-idea-2018-3-eap-high-contrast-theme-and-more-accessibility-improvements/), and it would be good to be able to allow users to opt in to these themes on all sites which support a common theming mechanism, such as a media query.
- *Enhanced contrast*, along the lines of OS X's setting and Gmail's current high contrast theme, which retain much of the "standard" palette and level of detail but enhance borders and increase text contrast to around the WCAG AAA level or better. The WCAG AAA level is intended for users with moderate vision impairments with a visual acuity of 20/80-20/40.
- *Acceptable contrast*, which is denoted by [WCAG AA](https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html) level. This is intended to be a standard contrast level perceivable by people with 20/40 vision or better - considered "minimal vision impairment" and comprising around 10% of the population of a typical wealthy country.
- There is also a small subset users who prefer *reduced contrast* for various health reasons.

These seem to map nicely onto the levels in https://github.com/w3c/csswg-drafts/issues/2943#issuecomment-437613516 - although we seem to have lost the concept of "forced" from https://github.com/w3c/csswg-drafts/issues/443

I don't know that we'd want to conflate "high contrast" and "enhanced contrast", since they really look quite different and target different audiences. Perhaps they'd need to be separate boolean queries?

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Received on Tuesday, 8 January 2019 03:40:16 UTC