ladybird/Libraries/LibWeb/HTML/HTMLDialogElement.cpp

/*
 * Copyright (c) 2020, the SerenityOS developers.
 * Copyright (c) 2024-2025, Sam Atkins <sam@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibJS/Runtime/NativeFunction.h>
#include <LibWeb/Bindings/HTMLDialogElementPrototype.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/Bindings/PrincipalHostDefined.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Event.h>
#include <LibWeb/DOM/IDLEventListener.h>
#include <LibWeb/HTML/CloseWatcher.h>
#include <LibWeb/HTML/Focus.h>
#include <LibWeb/HTML/HTMLDialogElement.h>
#include <LibWeb/HTML/ToggleEvent.h>
#include <LibWeb/HTML/TraversableNavigable.h>
#include <LibWeb/UIEvents/EventNames.h>
#include <LibWeb/UIEvents/PointerEvent.h>

namespace Web::HTML {

GC_DEFINE_ALLOCATOR(HTMLDialogElement);

HTMLDialogElement::HTMLDialogElement(DOM::Document& document, DOM::QualifiedName qualified_name)
    : HTMLElement(document, move(qualified_name))
{
}

HTMLDialogElement::~HTMLDialogElement() = default;

void HTMLDialogElement::initialize(JS::Realm& realm)
{
    WEB_SET_PROTOTYPE_FOR_INTERFACE(HTMLDialogElement);
    Base::initialize(realm);
}

void HTMLDialogElement::visit_edges(JS::Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);

    visitor.visit(m_close_watcher);
    visitor.visit(m_request_close_source_element);
    visitor.visit(m_previously_focused_element);
}

void HTMLDialogElement::removed_from(Node* old_parent, Node& old_root)
{
    HTMLElement::removed_from(old_parent, old_root);

    // 1. If removedNode's close watcher is not null, then:
    if (m_close_watcher) {
        // 1.1. Destroy removedNode's close watcher.
        m_close_watcher->destroy();
        // 1.2. Set removedNode's close watcher to null.
        m_close_watcher = nullptr;
    }

    // 2. If removedNode's node document's top layer contains removedNode, then remove an element from the top layer
    //    immediately given removedNode.
    if (document().top_layer_elements().contains(*this))
        document().remove_an_element_from_the_top_layer_immediately(*this);
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#queue-a-dialog-toggle-event-task
void HTMLDialogElement::queue_a_dialog_toggle_event_task(AK::String old_state, AK::String new_state, GC::Ptr<DOM::Element> source)
{
    // 1. If element's dialog toggle task tracker is not null, then:
    if (m_dialog_toggle_task_tracker.has_value()) {
        // 1. Set oldState to element's dialog toggle task tracker's old state.
        old_state = m_dialog_toggle_task_tracker->old_state;

        // 2. Remove element's dialog toggle task tracker's task from its task queue.
        HTML::main_thread_event_loop().task_queue().remove_tasks_matching([&](auto const& task) {
            return task.id() == m_dialog_toggle_task_tracker->task_id;
        });

        // 3. Set element's dialog toggle task tracker to null.
        m_dialog_toggle_task_tracker = {};
    }

    // 2. Queue an element task given the DOM manipulation task source and element to run the following steps:
    auto task_id = queue_an_element_task(Task::Source::DOMManipulation, [this, old_state, new_state = move(new_state), source]() {
        // 1. Fire an event named toggle at element, using ToggleEvent, with the oldState attribute initialized to
        //    oldState, the newState attribute initialized to newState, and the source attribute initialized to source.
        ToggleEventInit event_init {};
        event_init.old_state = move(old_state);
        event_init.new_state = move(new_state);

        dispatch_event(ToggleEvent::create(realm(), HTML::EventNames::toggle, move(event_init), source));

        // 2. Set element's dialog toggle task tracker to null.
        m_dialog_toggle_task_tracker = {};
    });

    // 3. Set element's dialog toggle task tracker to a struct with task set to the just-queued task and old state set to oldState.
    m_dialog_toggle_task_tracker = ToggleTaskTracker {
        .task_id = task_id,
        .old_state = move(old_state),
    };
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-show
WebIDL::ExceptionOr<void> HTMLDialogElement::show()
{
    // 1. If this has an open attribute and the is modal flag of this is false, then return.
    if (has_attribute(AttributeNames::open) && !m_is_modal)
        return {};

    // 2. If this has an open attribute, then throw an "InvalidStateError" DOMException.
    if (has_attribute(AttributeNames::open))
        return WebIDL::InvalidStateError::create(realm(), "Dialog already open"_utf16);

    // 3. If the result of firing an event named beforetoggle, using ToggleEvent,
    //  with the cancelable attribute initialized to true, the oldState attribute initialized to "closed",
    //  and the newState attribute initialized to "open" at this is false, then return.
    ToggleEventInit event_init {};
    event_init.cancelable = true;
    event_init.old_state = "closed"_string;
    event_init.new_state = "open"_string;

    auto beforetoggle_result = dispatch_event(ToggleEvent::create(realm(), HTML::EventNames::beforetoggle, move(event_init)));
    if (!beforetoggle_result)
        return {};

    // 4. If this has an open attribute, then return.
    if (has_attribute(AttributeNames::open))
        return {};

    // 5. Queue a dialog toggle event task given this, "closed", "open", and null.
    queue_a_dialog_toggle_event_task("closed"_string, "open"_string, nullptr);

    // 6. Add an open attribute to this, whose value is the empty string.
    TRY(set_attribute(AttributeNames::open, String {}));

    // 7. Assert: this's node document's open dialogs list does not contain this.
    VERIFY(!m_document->open_dialogs_list().contains_slow(GC::Ref(*this)));

    // 8. Add this to this's node document's open dialogs list.
    m_document->open_dialogs_list().append(*this);

    // 9. Set the dialog close watcher with this.
    set_close_watcher();

    // 10. Set this's previously focused element to the focused element.
    m_previously_focused_element = document().focused_area();

    // 11. Let document be this's node document.
    auto document = m_document;

    // 12. Let hideUntil be the result of running topmost popover ancestor given this, document's showing hint popover list, null, and false.
    Variant<GC::Ptr<HTMLElement>, GC::Ptr<DOM::Document>> hide_until = topmost_popover_ancestor(this, document->showing_hint_popover_list(), nullptr, IsPopover::No);

    // 13. If hideUntil is null, then set hideUntil to the result of running topmost popover ancestor given this, document's showing auto popover list, null, and false.
    if (!hide_until.get<GC::Ptr<HTMLElement>>())
        hide_until = topmost_popover_ancestor(this, document->showing_auto_popover_list(), nullptr, IsPopover::No);

    // 14. If hideUntil is null, then set hideUntil to document.
    if (!hide_until.get<GC::Ptr<HTMLElement>>())
        hide_until = document;

    // 15. Run hide all popovers until given hideUntil, false, and true.
    hide_all_popovers_until(hide_until, FocusPreviousElement::No, FireEvents::Yes);

    // 16. Run the dialog focusing steps given this.
    run_dialog_focusing_steps();

    return {};
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-showmodal
WebIDL::ExceptionOr<void> HTMLDialogElement::show_modal()
{
    // The showModal() method steps are to show a modal dialog given this and null.
    return show_a_modal_dialog(*this, nullptr);
}

WebIDL::ExceptionOr<void> HTMLDialogElement::show_a_modal_dialog(HTMLDialogElement& subject, GC::Ptr<DOM::Element> source)
{
    // To show a modal dialog given a dialog element subject:
    auto& realm = subject.realm();

    // 1. If subject has an open attribute and is modal of subject is true, then return.
    if (subject.has_attribute(AttributeNames::open) && subject.m_is_modal)
        return {};

    // 2. If subject has an open attribute, then throw an "InvalidStateError" DOMException.
    if (subject.has_attribute(AttributeNames::open))
        return WebIDL::InvalidStateError::create(realm, "Dialog already open"_utf16);

    // 3. If subject's node document is not fully active, then throw an "InvalidStateError" DOMException.
    if (!subject.document().is_fully_active())
        return WebIDL::InvalidStateError::create(realm, "Document is not fully active"_utf16);

    // 4. If subject is not connected, then throw an "InvalidStateError" DOMException.
    if (!subject.is_connected())
        return WebIDL::InvalidStateError::create(realm, "Dialog not connected"_utf16);

    // 5. If subject is in the popover showing state, then throw an "InvalidStateError" DOMException.
    if (subject.popover_visibility_state() == PopoverVisibilityState::Showing)
        return WebIDL::InvalidStateError::create(realm, "Dialog already open as popover"_utf16);

    // 6. If the result of firing an event named beforetoggle, using ToggleEvent,
    //  with the cancelable attribute initialized to true, the oldState attribute initialized to "closed",
    //  the newState attribute initialized to "open", and the source attribute initialized to source at subject is false, then return.
    ToggleEventInit event_init {};
    event_init.cancelable = true;
    event_init.old_state = "closed"_string;
    event_init.new_state = "open"_string;

    auto beforetoggle_result = subject.dispatch_event(ToggleEvent::create(realm, EventNames::beforetoggle, move(event_init), source));
    if (!beforetoggle_result)
        return {};

    // 7. If subject has an open attribute, then return.
    if (subject.has_attribute(AttributeNames::open))
        return {};

    // 8. If subject is not connected, then return.
    if (!subject.is_connected())
        return {};

    // 9. If subject is in the popover showing state, then return.
    if (subject.popover_visibility_state() == PopoverVisibilityState::Showing)
        return {};

    // 10. Queue a dialog toggle event task given subject, "closed", "open", and source.
    subject.queue_a_dialog_toggle_event_task("closed"_string, "open"_string, source);

    // 11. Add an open attribute to subject, whose value is the empty string.
    TRY(subject.set_attribute(AttributeNames::open, String {}));

    // 12. Set is modal of subject to true.
    subject.set_is_modal(true);

    // 13. Assert: subject's node document's open dialogs list does not contain subject.
    // AD-HOC: This assertion is skipped because it fails if the open attribute was removed before calling showModal()
    // See https://github.com/whatwg/html/issues/10953 and https://github.com/whatwg/html/pull/10954
    // VERIFY(!subject.document().open_dialogs_list().contains_slow(GC::Ref(subject)));

    // 14. Add subject to subject's node document's open dialogs list.
    subject.document().open_dialogs_list().append(subject);

    // FIXME: 15. Set subject's node document to be blocked by the modal dialog subject.

    // 16. If subject's node document's top layer does not already contain subject, then add an element to the top layer given subject.
    if (!subject.document().top_layer_elements().contains(subject))
        subject.document().add_an_element_to_the_top_layer(subject);

    // 17. Set the dialog close watcher with subject.
    subject.set_close_watcher();

    // FIXME: 18. Set subject's previously focused element to the focused element.

    // 19. Let document be subject's node document.
    auto& document = subject.document();

    // 20. Let hideUntil be the result of running topmost popover ancestor given subject, document's showing hint popover list, null, and false.
    Variant<GC::Ptr<HTMLElement>, GC::Ptr<DOM::Document>> hide_until = topmost_popover_ancestor(subject, document.showing_hint_popover_list(), nullptr, IsPopover::No);

    // 21. If hideUntil is null, then set hideUntil to the result of running topmost popover ancestor given subject, document's showing auto popover list, null, and false.
    if (!hide_until.get<GC::Ptr<HTMLElement>>())
        hide_until = topmost_popover_ancestor(subject, document.showing_auto_popover_list(), nullptr, IsPopover::No);

    // 22. If hideUntil is null, then set hideUntil to document.
    if (!hide_until.get<GC::Ptr<HTMLElement>>())
        hide_until = GC::Ptr(document);

    // 23. Run hide all popovers until given hideUntil, false, and true.
    hide_all_popovers_until(hide_until, FocusPreviousElement::No, FireEvents::Yes);

    // 24. Run the dialog focusing steps given subject.
    subject.run_dialog_focusing_steps();

    return {};
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-close
void HTMLDialogElement::close(Optional<String> return_value)
{
    // 1. If returnValue is not given, then set it to null.
    // 2. Close the dialog this with returnValue and null.
    close_the_dialog(move(return_value), nullptr);
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-requestclose
void HTMLDialogElement::request_close(Optional<String> return_value)
{
    // 1. If returnValue is not given, then set it to null.
    // 2. Request to close the dialog this with returnValue and null.
    request_close_the_dialog(move(return_value), nullptr);
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dialog-request-close
void HTMLDialogElement::request_close_the_dialog(Optional<String> return_value, GC::Ptr<DOM::Element> source)
{
    // 1. If this does not have an open attribute, then return.
    if (!has_attribute(AttributeNames::open))
        return;
    // AD-HOC: 2. If this's close watcher is null, then close the dialog this with returnValue and source, and return. See https://github.com/whatwg/html/pull/10983
    if (!m_close_watcher) {
        close_the_dialog(move(return_value), source);
        return;
    }
    // 3. Set dialog's enable close watcher for requestClose() to true.
    // AD-HOC: Implemented slightly differently to the spec, as the spec is unnecessarily complex.
    m_close_watcher->set_enabled(true);
    // 4. If returnValue is not given, then set it to null.
    // 5. Set this's request close return value to returnValue.
    m_request_close_return_value = return_value;
    // 6. Set subject's request close source element to source.
    m_request_close_source_element = source;
    // 6. Request to close dialog's close watcher with false.
    m_close_watcher->request_close(false);
    // 7. Set dialog's enable close watcher for requestClose() to false.
    // AD-HOC: Implemented slightly differently to the spec, as the spec is unnecessarily complex.
    // FIXME: This should be set based on dialog closedby state, when implemented.
    if (m_close_watcher)
        m_close_watcher->set_enabled(m_is_modal);
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-returnvalue
String HTMLDialogElement::return_value() const
{
    return m_return_value;
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dom-dialog-returnvalue
void HTMLDialogElement::set_return_value(String return_value)
{
    m_return_value = move(return_value);
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#close-the-dialog
void HTMLDialogElement::close_the_dialog(Optional<String> result, GC::Ptr<DOM::Element> source)
{
    // 1. If subject does not have an open attribute, then return.
    if (!has_attribute(AttributeNames::open))
        return;

    // 2. Fire an event named beforetoggle, using ToggleEvent, with the oldState attribute initialized to "open", the newState attribute initialized to "closed", and the source attribute initialized to source at subject.
    ToggleEventInit event_init {};
    event_init.old_state = "open"_string;
    event_init.new_state = "closed"_string;

    dispatch_event(ToggleEvent::create(realm(), HTML::EventNames::beforetoggle, move(event_init), source));

    // 3. If subject does not have an open attribute, then return.
    if (!has_attribute(AttributeNames::open))
        return;

    // 4. Queue a dialog toggle event task given subject, "open", "closed", and source.
    queue_a_dialog_toggle_event_task("open"_string, "closed"_string, source);

    // 5. Remove subject's open attribute.
    remove_attribute(AttributeNames::open);

    // 6. If the is modal flag of subject is true, then request an element to be removed from the top layer given subject.
    if (m_is_modal)
        document().request_an_element_to_be_remove_from_the_top_layer(*this);

    // 7. Let wasModal be the value of subject's is modal flag.
    auto was_modal = m_is_modal;

    // 8. Set the is modal flag of subject to false.
    set_is_modal(false);

    // 9. Remove subject from subject's node document's open dialogs list.
    document().open_dialogs_list().remove_first_matching([this](auto other) { return other == this; });

    // 10. If result is not null, then set subject's return value to result.
    if (result.has_value())
        set_return_value(result.release_value());

    // 11. Set subject's request close return value to null.
    m_request_close_return_value = {};

    // 12. Set subject's request close source element to null.
    m_request_close_source_element = nullptr;

    // 13. If subject's previously focused element is not null, then:
    if (m_previously_focused_element) {
        // 1. Let element be subject's previously focused element.
        auto element = m_previously_focused_element;

        // 2. Set subject's previously focused element to null.
        m_previously_focused_element = nullptr;

        // 3. If subject's node document's focused area of the document's DOM anchor is a shadow-including inclusive descendant of subject,
        //    or wasModal is true, then run the focusing steps for element; the viewport should not be scrolled by doing this step.
        auto focused_element = document().focused_area();
        auto is_focus_within_dialog = focused_element && focused_element->is_shadow_including_inclusive_descendant_of(*this);
        if (is_focus_within_dialog || was_modal)
            run_focusing_steps(element);
    }

    // 14. Queue an element task on the user interaction task source given the subject element to fire an event named close at subject.
    queue_an_element_task(HTML::Task::Source::UserInteraction, [this] {
        auto close_event = DOM::Event::create(realm(), HTML::EventNames::close);
        dispatch_event(close_event);
    });

    // 15. If subject's close watcher is not null, then:
    if (m_close_watcher) {
        // 1. Destroy subject's close watcher.
        m_close_watcher->destroy();
        // 2. Set subject's close watcher to null.
        m_close_watcher = nullptr;
    }
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#set-the-dialog-close-watcher
void HTMLDialogElement::set_close_watcher()
{
    // 1. Set dialog's close watcher to the result of establishing a close watcher given dialog's relevant global object, with:
    m_close_watcher = CloseWatcher::establish(*document().window());
    // - cancelAction given canPreventClose being to return the result of firing an event named cancel at dialog, with the cancelable attribute initialized to canPreventClose.
    auto cancel_callback_function = JS::NativeFunction::create(
        realm(), [this](JS::VM& vm) {
            auto& event = as<DOM::Event>(vm.argument(0).as_object());
            bool can_prevent_close = event.cancelable();
            auto should_continue = dispatch_event(DOM::Event::create(realm(), HTML::EventNames::cancel, { .cancelable = can_prevent_close }));
            if (!should_continue)
                event.prevent_default();
            return JS::js_undefined();
        },
        0, Utf16FlyString {}, &realm());
    auto cancel_callback = realm().heap().allocate<WebIDL::CallbackType>(*cancel_callback_function, realm());
    m_close_watcher->add_event_listener_without_options(HTML::EventNames::cancel, DOM::IDLEventListener::create(realm(), cancel_callback));
    // - closeAction being to close the dialog given dialog, dialog's request close return value, and dialog's request close source element.
    auto close_callback_function = JS::NativeFunction::create(
        realm(), [this](JS::VM&) {
            close_the_dialog(m_request_close_return_value, m_request_close_source_element);

            return JS::js_undefined();
        },
        0, Utf16FlyString {}, &realm());
    auto close_callback = realm().heap().allocate<WebIDL::CallbackType>(*close_callback_function, realm());
    m_close_watcher->add_event_listener_without_options(HTML::EventNames::close, DOM::IDLEventListener::create(realm(), close_callback));
    // - getEnabledState being to return true if dialog's enable close watcher for requestClose() is true or dialog's computed closed-by state is not None; otherwise false.
    // ADHOC: Implemented slightly differently to the spec, as the spec is unnecessarily complex.
    // FIXME: This should be set based on dialog closedby state, when implemented.
    m_close_watcher->set_enabled(m_is_modal);
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#dialog-focusing-steps
void HTMLDialogElement::run_dialog_focusing_steps()
{
    // 1. If the allow focus steps given subject's node document return false, then return.
    if (!document().allow_focus())
        return;

    // 2. Let control be null
    GC::Ptr<Element> control = nullptr;

    // FIXME 3. If subject has the autofocus attribute, then set control to subject.
    // FIXME 4. If control is null, then set control to the focus delegate of subject.

    // 5. If control is null, then set control to subject.
    if (!control)
        control = this;

    // 6. Run the focusing steps for control.
    run_focusing_steps(control);

    // 7. Let topDocument be control's node navigable's top-level traversable's active document.
    auto top_document = control->navigable()->top_level_traversable()->active_document();

    // 8. If control's node document's origin is not the same as the origin of topDocument, then return.
    if (!control->document().origin().is_same_origin(top_document->origin()))
        return;

    // FIXME: 9. Empty topDocument's autofocus candidates.
    // FIXME: 10. Set topDocument's autofocus processed flag to true.
}

void HTMLDialogElement::set_is_modal(bool is_modal)
{
    if (m_is_modal == is_modal)
        return;
    m_is_modal = is_modal;
    invalidate_style(DOM::StyleInvalidationReason::HTMLDialogElementSetIsModal);
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#the-dialog-element:is-valid-invoker-command-steps
bool HTMLDialogElement::is_valid_invoker_command(String& command)
{
    // 1. If command is in the Close state, the Request Close state, or the Show Modal state, then return true.
    if (command == "close" || command == "request-close" || command == "show-modal")
        return true;

    // 2. Return false.
    return false;
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#the-dialog-element:invoker-command-steps
void HTMLDialogElement::invoker_command_steps(DOM::Element& invoker, String& command)
{
    // 1. If element is in the popover showing state, then return.
    if (popover_visibility_state() == PopoverVisibilityState::Showing) {
        return;
    }

    // 2. If command is in the Close state and element has an open attribute,
    //    then close the dialog given element with invoker's optional value and invoker.
    if (command == "close" && has_attribute(AttributeNames::open)) {
        auto const optional_value = as<FormAssociatedElement>(invoker).optional_value();
        close_the_dialog(optional_value, invoker);
    }

    // 3. If command is in the Request Close state and element has an open attribute,
    //    then request to close the dialog element with invoker's optional value and invoker.
    if (command == "request-close" && has_attribute(AttributeNames::open)) {
        auto const optional_value = as<FormAssociatedElement>(invoker).optional_value();
        request_close_the_dialog(optional_value, invoker);
    }

    // 4. If command is the Show Modal state and element does not have an open attribute, then show a modal dialog given element and invoker.
    if (command == "show-modal" && !has_attribute(AttributeNames::open)) {
        MUST(show_a_modal_dialog(*this, invoker));
    }
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#nearest-clicked-dialog
GC::Ptr<HTMLDialogElement> HTMLDialogElement::nearest_clicked_dialog(UIEvents::PointerEvent const& event, GC::Ptr<DOM::Node> const target)
{
    // To find the nearest clicked dialog, given a PointerEvent event:

    // 1. Let target be event's target.

    // 2. If target is a dialog element, target has an open attribute, target's is modal is true, and event's clientX and clientY are outside the bounds of target, then return null.
    if (auto const* target_dialog = as_if<HTMLDialogElement>(*target); target_dialog
        && target_dialog->has_attribute(AttributeNames::open)
        && target_dialog->is_modal()
        && !target_dialog->get_bounding_client_rect().to_type<double>().contains(event.client_x(), event.client_y()))
        return {};

    // 3. Let currentNode be target.
    auto current_node = target;

    // 4. While currentNode is not null:
    while (current_node) {
        // 1. If currentNode is a dialog element and currentNode has an open attribute, then return currentNode.
        if (auto* current_dialog = as_if<HTMLDialogElement>(*current_node); current_dialog
            && current_dialog->has_attribute(AttributeNames::open))
            return current_dialog;

        // 2. Set currentNode to currentNode's parent in the flat tree.
        current_node = current_node->shadow_including_first_ancestor_of_type<HTMLElement>();
    }

    // 5. Return null.
    return {};
}

// https://html.spec.whatwg.org/multipage/interactive-elements.html#light-dismiss-open-dialogs
void HTMLDialogElement::light_dismiss_open_dialogs(UIEvents::PointerEvent const& event, GC::Ptr<DOM::Node> const target)
{
    // To light dismiss open dialogs, given a PointerEvent event:

    // 1. Assert: event's isTrusted attribute is true.
    VERIFY(event.is_trusted());

    // 2. Let document be event's target's node document.
    // FIXME: The event's target hasn't been initialized yet, so it's passed as an argument
    auto& document = target->document();

    // 3. If document's open dialogs list is empty, then return.
    if (document.open_dialogs_list().is_empty())
        return;

    // 4. Let ancestor be the result of running nearest clicked dialog given event.
    auto const ancestor = nearest_clicked_dialog(event, target);

    // 5. If event's type is "pointerdown", then set document's dialog pointerdown target to ancestor.
    if (event.type() == UIEvents::EventNames::pointerdown)
        document.set_dialog_pointerdown_target(ancestor);

    // 6. If event's type is "pointerup", then:
    if (event.type() == UIEvents::EventNames::pointerup) {
        // 1. Let sameTarget be true if ancestor is document's dialog pointerdown target.
        bool const same_target = ancestor == document.dialog_pointerdown_target();

        // 2. Set document's dialog pointerdown target to null.
        document.set_dialog_pointerdown_target({});

        // 3. If sameTarget is false, then return.
        if (!same_target)
            return;

        // 4. Let topmostDialog be the last element of document's open dialogs list.
        auto const topmost_dialog = document.open_dialogs_list().last();

        // 5. If ancestor is topmostDialog, then return.
        if (ancestor == topmost_dialog)
            return;

        // 6. If topmostDialog's computed closed-by state is not Any, then return.
        // FIXME: This should use the "computed closed-by state" algorithm.
        auto closedby = topmost_dialog->attribute(AttributeNames::closedby);
        if (!closedby.has_value() || !closedby.value().equals_ignoring_ascii_case("any"sv))
            return;

        // 7. Assert: topmostDialog's close watcher is not null.
        VERIFY(topmost_dialog->m_close_watcher);

        // 8. Request to close topmostDialog's close watcher with false.
        topmost_dialog->request_close({});
    }
}

}