:focus-within pseudo class doesn't get invalidated when frame loses focus

[Ryosuke Niwa]

Created attachment 460764 [details]
test case

Reproduction steps:
1. Open the attached document in Safari / Mini browser
2. Focus the address bar / other parts of app

Expected result:
There will be 100px by 100px green box

Actual result:
Green box remains 50px by 50px

[Ryosuke Niwa]

Created attachment 460765 [details]
WIP

This patch doesn't quite work.

Replacing
Style::PseudoClassChangeInvalidation focusStyleInvalidation(lineage, { { CSSSelector::PseudoClassFocusWithin, activeAndFocused } });
with
lineage.invalidateStyle();
makes it work.

[Ryosuke Niwa]

So :focus, :focus-within, :focus-visible all depend on FrameSelection::isFocusedAndActive() via isFrameFocused in SelectorCheckerTestFunctions.h

FrameSelection::isFocusedAndActive() in turn is defined in terms of two boolean states: FrameSelection::m_focused and FocusController::isActive().

FocusController calls FrameSelection::pageActivationChanged() whenever isActive state changes on the focused frame's FrameSelection.

In the ideal world, we have a single place where these two boolean states are updated at once, and that's where we instantiate relevant Style::PseudoClassChangeInvalidation but that's tricky because FocusController is a per-Page concept and FrameSelection is per-Frame concept.

To reconcile, I could imagine a few solutions:
1. Add a new boolean m_isPageActive to FrameSelection which gets sync'ed when FrameSelection becomes newly focused (inside FrameSelection::setFocused). We then update both m_focused & this new boolean whilst we have Style::PseudoClassChangeInvalidation.

2. In FrameSelection::focusedOrActiveStateChanged(), introduce a temporary override for FrameSelection::isFocusedAndActive(), which makes the function return the negative value while Style::PseudoClassChangeInvalidation are instantiated.

3. Simply use Element::invalidateStyle() on these elements for now. This will only occur when WKWebView becomes first responder or resigns first responder (i.e. view gets focused or unfocused in more Web / Windows terminology).

[Ryosuke Niwa]

Created attachment 460776 [details]
WIP2

[Ryosuke Niwa]

Pull request: https://github.com/WebKit/WebKit/pull/2259

[EWS]

Committed 252324@main (ac8282feee7f): <https://commits.webkit.org/252324@main>

Reviewed commits have been landed. Closing PR #2259 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/96786471>