Default link colors lack sufficient contrast in the dark color scheme

[pxlcoder]

5413aa7

Default link colors lack sufficient contrast in the dark color scheme
https://bugs.webkit.org/show_bug.cgi?id=209851
rdar://61149466

Reviewed by Tim Nguyen and Megan Gardner.

Currently, link colors are the same in both the light and dark color schemes.
This results in a lack of contrast against dark backgrounds.

To fix, dark-mode specific link colors are defined. The definitions match the
values used by Chromium, and are not taken from the system link color. This
approach was chosen as the default link color in the light color scheme is
defined by https://html.spec.whatwg.org/multipage/rendering.html#phrasing-content-3,
and also does not come from the system.

* LayoutTests/css-dark-mode/link-colors-expected.html: Added.
* LayoutTests/css-dark-mode/link-colors.html: Added.
* Source/WebCore/dom/Document.cpp:

Link colors can be adjusted by HTML using the `link`, `alink`, and `vlink`
attributes. Adjust logic to ensure that a static link color is only used if the
corresponding attribute is specified. Without these changes, the dark mode
color would never be used, as the light mode color is stored as the default.

(WebCore::Document::linkColor const):
(WebCore::Document::visitedLinkColor const):
(WebCore::Document::activeLinkColor const):
(WebCore::Document::resetLinkColor):
(WebCore::Document::resetVisitedLinkColor):
(WebCore::Document::resetActiveLinkColor):
* Source/WebCore/dom/Document.h:
(WebCore::Document::linkColor const): Deleted.
(WebCore::Document::visitedLinkColor const): Deleted.
(WebCore::Document::activeLinkColor const): Deleted.
* Source/WebCore/rendering/RenderTheme.cpp:
(WebCore::RenderTheme::systemColor const):

Add definitions for colors under the dark color scheme.

* Source/WebCore/style/ColorFromPrimitiveValue.cpp:
(WebCore::Style::colorFromPrimitiveValue):

Pass in `StyleColorOptions` when determining the link color, so that it can be
resolved against the used color scheme.

Canonical link: https://commits.webkit.org/267847@main

bfd7c04

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
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✅ 🧪 webkitperl	✅ 🧪 ios-wk2	⏳ 🧪 api-mac	✅ 🛠 gtk
	✅ 🧪 ios-wk2-wpt	⏳ 🧪 mac-wk1	✅ 🧪 gtk-wk2
	✅ 🧪 api-ios	⏳ 🧪 mac-wk2	✅ 🧪 api-gtk
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2
	✅ 🛠 tv-sim	✅ 🧪 mac-wk2-stress
✅ 🛠 🧪 merge	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 17513cf)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🛠 gtk
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🧪 gtk-wk2
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🧪 api-gtk
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[nt1m]

You can also add tests for :visited by doing <a href="">

[pxlcoder]

Updated – thanks!

[webkit-early-warning-system]

EWS run on previous version of this PR (hash b894898)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	⏳ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	⏳ 🛠 mac-AS-debug	⏳ 🧪 wpe-wk2
✅ 🧪 webkitperl	🧪 ios-wk2	🧪 api-mac	✅ 🛠 gtk
	🧪 ios-wk2-wpt	🧪 mac-wk1	⏳ 🧪 gtk-wk2
⏳ 🛠 🧪 jsc	🧪 api-ios	🧪 mac-wk2	🧪 api-gtk
	⏳ 🛠 tv	⏳ 🧪 mac-AS-debug-wk2
	⏳ 🛠 tv-sim	🧪 mac-wk2-stress
	⏳ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on previous version of this PR (hash d37f3fc)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	⏳ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	⏳ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	⏳ 🛠 mac-AS-debug	⏳ 🧪 wpe-wk2
✅ 🧪 webkitperl	🧪 ios-wk2	⏳ 🧪 api-mac	✅ 🛠 gtk
	⏳ 🧪 ios-wk2-wpt	⏳ 🧪 mac-wk1	⏳ 🧪 gtk-wk2
⏳ 🛠 🧪 jsc	🧪 api-ios	⏳ 🧪 mac-wk2	🧪 api-gtk
⏳ 🛠 🧪 jsc-arm64	⏳ 🛠 tv	⏳ 🧪 mac-AS-debug-wk2
	⏳ 🛠 tv-sim	🧪 mac-wk2-stress
	⏳ 🛠 watch
	⏳ 🛠 watch-sim

[hortont424]

constrast!

[webkit-early-warning-system]

EWS run on current version of this PR (hash bfd7c04)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	⏳ 🧪 api-mac	✅ 🛠 gtk
	✅ 🧪 ios-wk2-wpt	⏳ 🧪 mac-wk1	✅ 🧪 gtk-wk2
	✅ 🧪 api-ios	⏳ 🧪 mac-wk2	✅ 🧪 api-gtk
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2
	✅ 🛠 tv-sim	✅ 🧪 mac-wk2-stress
✅ 🛠 🧪 merge	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 267847@main (5413aa7): https://commits.webkit.org/267847@main

Reviewed commits have been landed. Closing PR #17512 and removing active labels.