Bug 212952 – Remove "no-preference" value for prefers-color-scheme media query

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Simon Fraser (smfr)]

See https://github.com/w3c/csswg-drafts/issues/3857#issuecomment-634779976 and https://groups.google.com/a/chromium.org/d/msg/blink-dev/3RhZFvZE1LM/t7BpLBWkAwAJ

[Tim Nguyen (:ntim)]

Created attachment 427530 [details]
Patch

[Antti Koivisto]

Comment on attachment 427530 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=427530&action=review

> Source/WebCore/css/MediaQueryEvaluator.cpp:-811
>      switch (keyword) {
> -    case CSSValueNoPreference:
> -        return false;

The default for this switch is false so this doesn't seem to change anything at all.

[Antti Koivisto]

Comment on attachment 427530 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=427530&action=review

> LayoutTests/css-dark-mode/older-systems/prefers-color-scheme.html:25
> -@media (prefers-color-scheme: no-preference) {
> +@media not (prefers-color-scheme) {

We may need to keep supporting 'no-preference' value even when parsing is fixed.

[Antti Koivisto]

Comment on attachment 427530 [details]
Patch

I don't know if it is ok to remove 'no-preference' support but if it is, it can be done after the parsing fix. It should also be done properly by removing all the code, not by stealth test changes.

[Tim Nguyen (:ntim)]

Comment on attachment 427530 [details]
Patch

Regarding tests: the test already tests for `foo` which is the invalid keyword case (like `no-preference`). WPT also has coverage for `no-preference`: https://wpt.fyi/results/css/mediaqueries/prefers-color-scheme.html?label=master&label=experimental&aligned&q=prefers-color-scheme

Regarding removing all the code: CSSValueNoPreference can't be removed since other MQ use it (prefers-contrast/prefers-reduced-motion).

[Antti Koivisto]

Tim Hatcher says getting rid of this is ok.

[EWS]

Committed r276908 (237253@main): <https://commits.webkit.org/237253@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 427530 [details].

[Radar WebKit Bug Importer]

<rdar://problem/77461590>