1506364 - Implement the prefers-contrast media-query

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement, P1)

Description

[Johan Ronsse]

Attachment: Screenshot 2018-11-10 at 15.35.45.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36

Steps to reproduce:

If the user set high contrast to “checked” in macOS, we can assume he or she will need high contrast in web sites as well. If we can add the feature to CSS that we can detect high contrast mode using CSS, it would be great.

@media (prefers-high-contrast: true) {
  /* CSS code */
}

Implementation could be much like prefers-reduced-motion https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-reduced-motion

Comment 1

[Timea Cernea [:tbabos][inactive]]

Hi Johan Ronsse,

I will set this issue as an enhancement for now. Hopefully, the component is the right one, if not please feel free to add it to the right one.

Thanks for the report!

Comment 2

[Emilio Cobos Álvarez (:emilio)]

There's actually something resembling a spec for this: https://drafts.csswg.org/mediaqueries-5/#prefers-contrast

Comment 3

[zekemedley]

Attachment: Bug 1506364 - Implement the prefers-contrast media-query. r=morgan,emilio

Comment 4

[zekemedley]

Attachment: Telemetry Request

Comment 5

[zekemedley]

We've decided that we're not actually going to enable telemetry. The plan now is:

1. Remove the telemetry
2. Enable prefers-contrast by default in browser chrome for use with a high contrast theme.
3. Enable prefers-contrast behind preference on the web.

Comment 6

[Simon Mainey]

Will this be covered by RFP? Much like prefers-reduced-motion (returns no-preference) in Bug 1479239 and prefers-color-scheme (returns light) in Bug 1494034

Comment 7

[Simon Mainey]

(In reply to Simon Mainey from comment #6)

Will this be covered by RFP?...

nvm

Comment 8

[zekemedley]

(In reply to Simon Mainey from comment #6)

Will this be covered by RFP? Much like prefers-reduced-motion (returns no-preference) in Bug 1479239 and prefers-color-scheme (returns light) in Bug 1494034

Our current plan is to return no-preference when RFP is enabled but still be honest about whether or not forced colors are in use. There is some discussion about this on phabricator here. This has to do with with the addition of a forced option to the media query recently.

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/eea7e31fdade
Implement the prefers-contrast media-query. r=morgan,emilio

Comment 10

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/eea7e31fdade

Comment 11

[Florian Scholz (Open Web Docs)]

Adding the intent to prototype here https://groups.google.com/g/mozilla.dev.platform/c/bTEmQxffGvA
Not yet enabled by default. Behind layout.css.prefers-contrast.enabled