<link> elements with media queries that do not affect the current page can be delayed

[anttijk]

9e31d4e

<link> elements with media queries that do not affect the current page can be delayed
https://bugs.webkit.org/show_bug.cgi?id=39455
rdar://102178226

Reviewed by Alan Baradlay.

We correctly deprioritize stylesheets with non-matching media attribute and don't make them
rendering blocking. However they may still delay the visually non-empty milestone. This delay
only comes into play if there is not enough visual content to trigger the milestone otherwise.
This may end up delaying rendering until the non-matching stylesheets are fully loaded on simple
pages.

* LayoutTests/http/tests/css/link-with-non-matching-media-slow-load-expected.html: Added.
* LayoutTests/http/tests/css/link-with-non-matching-media-slow-load.html: Added.
* Source/WebCore/page/FrameView.cpp:
(WebCore::FrameView::checkAndDispatchDidReachVisuallyNonEmptyState):

Ignore "very low" priority resources when determining if everything important is loaded.

* Source/WebCore/testing/Internals.cpp:
(WebCore::Internals::isVisuallyNonEmpty const):
* Source/WebCore/testing/Internals.h:
* Source/WebCore/testing/Internals.idl:

Testing support.

Canonical link: https://commits.webkit.org/259963@main

f30ff97

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

[webkit-early-warning-system]

EWS run on current version of this PR (hash f30ff97)

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

[pepelsbey]

Nice! Does it affect CSS files loaded via @import? There’s a similar issue in Chromium. These two should work the same:

<link rel="stylesheet" href="/style.css" media="(prefers-color-scheme: light)">

<style>
  @import url(import.css) (prefers-color-scheme: light)
</style>

[anttijk]

Nice! Does it affect CSS files loaded via @import? There’s a similar issue in Chromium. These two should work the same:

No, this PR is only about <link>. Currently media queries do not affect loading of @import rules at all, just applying. Worth a separate bug.

[webkit-commit-queue]

Committed 259963@main (9e31d4e): https://commits.webkit.org/259963@main

Reviewed commits have been landed. Closing PR #9746 and removing active labels.