LibWeb: Implement some viewport proximity features

[Psychpsyo]

This gets rid of some FIXMEs related to viewport proximity and relevancy to the user in the update the rendering algorithm.

I know there is no tests, but I tried some of the relevant WPT tests for the new sections and none of them are passing yet so I assume there is other code missing elsewhere that would need to actually make use of the element's proximity to the viewport. (beyond just setting it in this one place.)

So I don't think there is any sensible tests that can be written for these two functions on their own.

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[AtkinsSJ]

There are a couple of tests crashing on CI. They both look like flakes but I'm re-running CI just in case.

Otherwise this looks good.

[Psychpsyo]

There are a couple of tests crashing on CI. They both look like flakes but I'm re-running CI just in case.

Otherwise this looks good.

I am not quite sure how much of it is flaky and how much is a race condition.
I haven't had the time to properly look into this yet, but my current assumption is that, by the time "update the rendering" runs, something (the document element?) is still null.

But I am not sure.

[AtkinsSJ]

Pasting it here so it's easier to find. I would have thought that document->update_layout(); a few lines above would ensure that there's a document element though, this is very odd.

/Users/runner/work/ladybird/ladybird/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp:344:43: runtime error: member call on null pointer of type 'Web::DOM::Node'
    #0 0x1109a84d8 in Web::HTML::EventLoop::update_the_rendering() EventLoop.cpp:344
    #1 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #2 0x1109a3798 in Web::HTML::EventLoop::process() EventLoop.cpp:179
    #3 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #4 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #5 0x10472612c in Core::EventReceiver::dispatch_event(Core::Event&, Core::EventReceiver*) EventReceiver.cpp:162
    #6 0x10477bae4 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:121
    #7 0x10471a0f4 in Core::EventLoop::spin_until(AK::Function<bool ()>) EventLoop.cpp:95
    #8 0x1116147f4 in Web::Platform::EventLoopPluginSerenity::spin_until(GC::Root<GC::Function<bool ()>>) EventLoopPluginSerenity.cpp:19
    #9 0x1109a16ac in Web::HTML::EventLoop::spin_until(GC::Ref<GC::Function<bool ()>>) EventLoop.cpp:97
    #10 0x110fd8f9c in Web::HTML::TraversableNavigable::apply_the_history_step(int, bool, AK::Optional<Web::HTML::SourceSnapshotParams>, GC::Ptr<Web::HTML::Navigable>, AK::Optional<Web::HTML::UserNavigationInvolvement>, AK::Optional<Web::Bindings::NavigationType>, Web::HTML::TraversableNavigable::SynchronousNavigation) TraversableNavigable.cpp:672
    #11 0x110fe7830 in Web::HTML::TraversableNavigable::apply_the_push_or_replace_history_step(int, Web::HTML::HistoryHandlingBehavior, Web::HTML::TraversableNavigable::SynchronousNavigation) TraversableNavigable.cpp:1197
    #12 0x110d2b1a4 in Web::HTML::finalize_a_cross_document_navigation(GC::Ref<Web::HTML::Navigable>, Web::HTML::HistoryHandlingBehavior, GC::Ref<Web::HTML::SessionHistoryEntry>) Navigable.cpp:1933
    #13 0x110d500e4 in AK::Function<void ()>::CallableWrapper<Web::HTML::Navigable::navigate(Web::HTML::Navigable::NavigateParams)::$_2::operator()() const::'lambda0'()::operator()() const::'lambda'()>::call() Function.h:187
    #14 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #15 0x110f3899c in AK::Function<void ()>::CallableWrapper<Web::HTML::SessionHistoryTraversalQueue::SessionHistoryTraversalQueue()::$_0>::call() Function.h:187
    #16 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #17 0x10472612c in Core::EventReceiver::dispatch_event(Core::Event&, Core::EventReceiver*) EventReceiver.cpp:162
    #18 0x10477bae4 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:121
    #19 0x10471a0f4 in Core::EventLoop::spin_until(AK::Function<bool ()>) EventLoop.cpp:95
    #20 0x1116147f4 in Web::Platform::EventLoopPluginSerenity::spin_until(GC::Root<GC::Function<bool ()>>) EventLoopPluginSerenity.cpp:19
    #21 0x1109a16ac in Web::HTML::EventLoop::spin_until(GC::Ref<GC::Function<bool ()>>) EventLoop.cpp:97
    #22 0x110fdf0d0 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>, GC::Ptr<Web::HTML::TraversableNavigable>, AK::Optional<int>, AK::Optional<Web::HTML::UserNavigationInvolvement>) TraversableNavigable.cpp:992
    #23 0x110fe4004 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>) TraversableNavigable.cpp:1002
    #24 0x110d4c354 in AK::Function<void ()>::CallableWrapper<Web::HTML::Navigable::navigate(Web::HTML::Navigable::NavigateParams)::$_2>::call() Function.h:187
    #25 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #26 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #27 0x10477b9e0 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:118
    #28 0x10471a0f4 in Core::EventLoop::spin_until(AK::Function<bool ()>) EventLoop.cpp:95
    #29 0x1116147f4 in Web::Platform::EventLoopPluginSerenity::spin_until(GC::Root<GC::Function<bool ()>>) EventLoopPluginSerenity.cpp:19
    #30 0x1109a16ac in Web::HTML::EventLoop::spin_until(GC::Ref<GC::Function<bool ()>>) EventLoop.cpp:97
    #31 0x110d0ff08 in Web::HTML::create_navigation_params_by_fetching(GC::Ptr<Web::HTML::SessionHistoryEntry>, GC::Ptr<Web::HTML::Navigable>, Web::HTML::SourceSnapshotParams const&, Web::HTML::TargetSnapshotParams const&, Web::HTML::CSPNavigationType, AK::Optional<AK::String>) Navigable.cpp:892
    #32 0x110d069d8 in Web::HTML::Navigable::populate_session_history_entry_document(GC::Ptr<Web::HTML::SessionHistoryEntry>, Web::HTML::SourceSnapshotParams const&, Web::HTML::TargetSnapshotParams const&, AK::Optional<AK::String>, AK::Variant<AK::Optional<AK::StringView>, GC::Ref<Web::HTML::NavigationParams>, GC::Ref<Web::HTML::NonFetchSchemeNavigationParams>>, Web::HTML::CSPNavigationType, bool, GC::Ptr<GC::Function<void ()>>) Navigable.cpp:1110
    #33 0x110d4d624 in AK::Function<void ()>::CallableWrapper<Web::HTML::Navigable::navigate(Web::HTML::Navigable::NavigateParams)::$_2>::call() Function.h:187
    #34 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #35 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #36 0x10477b9e0 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:118
    #37 0x10471a0f4 in Core::EventLoop::spin_until(AK::Function<bool ()>) EventLoop.cpp:95
    #38 0x1116147f4 in Web::Platform::EventLoopPluginSerenity::spin_until(GC::Root<GC::Function<bool ()>>) EventLoopPluginSerenity.cpp:19
    #39 0x1109a16ac in Web::HTML::EventLoop::spin_until(GC::Ref<GC::Function<bool ()>>) EventLoop.cpp:97
    #40 0x110d0ff08 in Web::HTML::create_navigation_params_by_fetching(GC::Ptr<Web::HTML::SessionHistoryEntry>, GC::Ptr<Web::HTML::Navigable>, Web::HTML::SourceSnapshotParams const&, Web::HTML::TargetSnapshotParams const&, Web::HTML::CSPNavigationType, AK::Optional<AK::String>) Navigable.cpp:892
    #41 0x110d069d8 in Web::HTML::Navigable::populate_session_history_entry_document(GC::Ptr<Web::HTML::SessionHistoryEntry>, Web::HTML::SourceSnapshotParams const&, Web::HTML::TargetSnapshotParams const&, AK::Optional<AK::String>, AK::Variant<AK::Optional<AK::StringView>, GC::Ref<Web::HTML::NavigationParams>, GC::Ref<Web::HTML::NonFetchSchemeNavigationParams>>, Web::HTML::CSPNavigationType, bool, GC::Ptr<GC::Function<void ()>>) Navigable.cpp:1110
    #42 0x110d4d624 in AK::Function<void ()>::CallableWrapper<Web::HTML::Navigable::navigate(Web::HTML::Navigable::NavigateParams)::$_2>::call() Function.h:187
    #43 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #44 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #45 0x10477b9e0 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:118
    #46 0x10471a0f4 in Core::EventLoop::spin_until(AK::Function<bool ()>) EventLoop.cpp:95
    #47 0x1116147f4 in Web::Platform::EventLoopPluginSerenity::spin_until(GC::Root<GC::Function<bool ()>>) EventLoopPluginSerenity.cpp:19
    #48 0x1109a16ac in Web::HTML::EventLoop::spin_until(GC::Ref<GC::Function<bool ()>>) EventLoop.cpp:97
    #49 0x110fdf0d0 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>, GC::Ptr<Web::HTML::TraversableNavigable>, AK::Optional<int>, AK::Optional<Web::HTML::UserNavigationInvolvement>) TraversableNavigable.cpp:992
    #50 0x110fe4004 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>) TraversableNavigable.cpp:1002
    #51 0x110d4c354 in AK::Function<void ()>::CallableWrapper<Web::HTML::Navigable::navigate(Web::HTML::Navigable::NavigateParams)::$_2>::call() Function.h:187
    #52 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #53 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #54 0x10477b9e0 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:118
    #55 0x10471a0f4 in Core::EventLoop::spin_until(AK::Function<bool ()>) EventLoop.cpp:95
    #56 0x1116147f4 in Web::Platform::EventLoopPluginSerenity::spin_until(GC::Root<GC::Function<bool ()>>) EventLoopPluginSerenity.cpp:19
    #57 0x1109a16ac in Web::HTML::EventLoop::spin_until(GC::Ref<GC::Function<bool ()>>) EventLoop.cpp:97
    #58 0x110fdf0d0 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>, GC::Ptr<Web::HTML::TraversableNavigable>, AK::Optional<int>, AK::Optional<Web::HTML::UserNavigationInvolvement>) TraversableNavigable.cpp:992
    #59 0x110fe4004 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>) TraversableNavigable.cpp:1002
    #60 0x110d4c354 in AK::Function<void ()>::CallableWrapper<Web::HTML::Navigable::navigate(Web::HTML::Navigable::NavigateParams)::$_2>::call() Function.h:187
    #61 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #62 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #63 0x10477b9e0 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:118
    #64 0x10471a0f4 in Core::EventLoop::spin_until(AK::Function<bool ()>) EventLoop.cpp:95
    #65 0x1116147f4 in Web::Platform::EventLoopPluginSerenity::spin_until(GC::Root<GC::Function<bool ()>>) EventLoopPluginSerenity.cpp:19
    #66 0x1109a16ac in Web::HTML::EventLoop::spin_until(GC::Ref<GC::Function<bool ()>>) EventLoop.cpp:97
    #67 0x110fdf0d0 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>, GC::Ptr<Web::HTML::TraversableNavigable>, AK::Optional<int>, AK::Optional<Web::HTML::UserNavigationInvolvement>) TraversableNavigable.cpp:992
    #68 0x110fe4004 in Web::HTML::TraversableNavigable::check_if_unloading_is_canceled(AK::Vector<GC::Root<Web::HTML::Navigable>, 0ul>) TraversableNavigable.cpp:1002
    #69 0x110d4c354 in AK::Function<void ()>::CallableWrapper<Web::HTML::Navigable::navigate(Web::HTML::Navigable::NavigateParams)::$_2>::call() Function.h:187
    #70 0x10f97fa84 in AK::Function<void ()>::operator()() const Function.h:120
    #71 0x104729f58 in AK::Function<void ()>::operator()() const Function.h:120
    #72 0x10477b9e0 in Core::ThreadEventQueue::process() ThreadEventQueue.cpp:118
    #73 0x104789f04 in Core::EventLoopImplementationUnix::exec() EventLoopImplementationUnix.cpp:316
    #74 0x104719de4 in Core::EventLoop::exec() EventLoop.cpp:88
    #75 0x102432a58 in serenity_main(Main::Arguments) main.cpp:208
    #76 0x10289420c in main Main.cpp:39
    #77 0x193ad0270  (<unknown module>)

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /Users/runner/work/ladybird/ladybird/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp:344:43 in 
WebContent process crashed! Last page loaded: file:///Users/runner/work/ladybird/ladybird/Tests/LibWeb/Text/input/wpt-import/html/syntax/parsing/html5lib_tests10.html

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[Psychpsyo]

Pasting it here so it's easier to find. I would have thought that document->update_layout(); a few lines above would ensure that there's a document element though, this is very odd.

I've now just made it check if there is a document element and only iterate over the children if there is.
No document element should mean no elements to go through.