ladybird/Libraries/LibWeb/Layout/BlockFormattingContext.cpp

/*
 * Copyright (c) 2020-2022, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2025-2026, Jelle Raaijmakers <jelle@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/TemporaryChange.h>
#include <LibWeb/CSS/ComputedProperties.h>
#include <LibWeb/CSS/Length.h>
#include <LibWeb/CSS/PropertyID.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/Node.h>
#include <LibWeb/DOM/ShadowRoot.h>
#include <LibWeb/Dump.h>
#include <LibWeb/HTML/HTMLElement.h>
#include <LibWeb/Layout/BlockContainer.h>
#include <LibWeb/Layout/BlockFormattingContext.h>
#include <LibWeb/Layout/Box.h>
#include <LibWeb/Layout/FieldSetBox.h>
#include <LibWeb/Layout/InlineFormattingContext.h>
#include <LibWeb/Layout/LegendBox.h>
#include <LibWeb/Layout/LineBuilder.h>
#include <LibWeb/Layout/ListItemBox.h>
#include <LibWeb/Layout/ListItemMarkerBox.h>
#include <LibWeb/Layout/ReplacedBox.h>
#include <LibWeb/Layout/SVGSVGBox.h>
#include <LibWeb/Layout/TableWrapper.h>
#include <LibWeb/Layout/Viewport.h>

namespace Web::Layout {

BlockFormattingContext::BlockFormattingContext(LayoutState& state, LayoutMode layout_mode, BlockContainer const& root, FormattingContext* parent)
    : FormattingContext(Type::Block, layout_mode, state, root, parent)
{
}

BlockFormattingContext::~BlockFormattingContext()
{
    if (!m_was_notified_after_parent_dimensioned_my_root_box) {
        // HACK: The parent formatting context never notified us after assigning dimensions to our root box.
        //       Pretend that it did anyway, to make sure absolutely positioned children get laid out.
        // FIXME: Get rid of this hack once parent contexts behave properly.
        parent_context_did_dimension_child_root_box();
    }
}

CSSPixels BlockFormattingContext::automatic_content_width() const
{
    if (root().children_are_inline())
        return m_state.get(root()).content_width();
    return greatest_child_width(root());
}

CSSPixels BlockFormattingContext::automatic_content_height() const
{
    return compute_auto_height_for_block_formatting_context_root(root());
}

static bool margins_collapse_through(Box const& box, LayoutState& state)
{
    // https://drafts.csswg.org/css2/#adjoining-margins
    // Two margins are adjoining if and only if:
    // - both belong to in-flow block-level boxes that participate in the same block formatting context
    //   NB: Yes, we're dealing with one and the same box here.

    // - no line boxes, no clearance, no padding and no border separate them (Note that certain zero-height line boxes
    //   (see 9.4.2) are ignored for this purpose.)
    // NB: Border and padding are handled further down.
    if (box.computed_values().clear() != CSS::Clear::None)
        return false;

    // - both belong to vertically-adjacent box edges, i.e. form one of the following pairs:
    //   - top and bottom margins of a box that does not establish a new block formatting context and that has zero
    //     computed 'min-height', zero or 'auto' computed 'height', and no in-flow children
    if (FormattingContext::creates_block_formatting_context(box))
        return false;

    // NB: This should take care of the height and min-height constraints.
    //     ( also see https://github.com/w3c/csswg-drafts/pull/13699#issuecomment-4103045370 for spec ambiguity )
    if (state.get(box).border_box_height() != 0)
        return false;

    // https://drafts.csswg.org/css-sizing-4/#aspect-ratio-margin-collapse
    // FIXME: For the purpose of margin collapsing (CSS 2 §8.3.1 Collapsing margins), if the block axis is the
    //        ratio-dependent axis, it is not considered to have a computed block-size of auto.

    // AD-HOC: The "and no in-flow children" above is wrong. (see https://github.com/w3c/csswg-drafts/pull/13699 )
    for (auto const* child = box.first_child_of_type<Box>(); child; child = child->next_sibling_of_type<Box>()) {
        if (child->is_out_of_flow())
            continue;
        if (!margins_collapse_through(*child, state))
            return false;
    }

    return true;
}

void BlockFormattingContext::run(AvailableSpace const& available_space)
{
    FORMATTING_CONTEXT_TRACE();
    // https://drafts.csswg.org/css-multicol-2/#the-multi-column-model
    auto root_state = m_state.get(root());
    auto column_count = determine_used_value_for_column_count(root_state.content_width());
    if (column_count.has_value()) {
        auto column_width = determine_used_value_for_column_width(root_state.content_width(), column_count.value());
        // FIXME: Do multi-column layout.
        (void)column_width;
    }

    if (auto const* fieldset_box = as_if<FieldSetBox>(root()); fieldset_box && fieldset_box->rendered_legend()) {
        layout_fieldset_with_rendered_legend(*fieldset_box, available_space);
        return;
    }

    if (root().children_are_inline())
        layout_inline_children(root(), available_space);
    else
        layout_block_level_children(root(), available_space);

    // Fieldsets without a rendered legend skip collapsed margin assignment.
    if (is<FieldSetBox>(root()))
        return;

    // Assign collapsed margin left after children layout of formatting context to the last child box
    if (m_margin_state.current_collapsed_margin() != 0) {
        for (auto* child_box = root().last_child_of_type<Box>(); child_box; child_box = child_box->previous_sibling_of_type<Box>()) {
            if (child_box->is_absolutely_positioned() || child_box->is_floating())
                continue;
            if (margins_collapse_through(*child_box, m_state))
                continue;
            m_state.get_mutable(*child_box).margin_bottom = m_margin_state.current_collapsed_margin();
            break;
        }
    }
}

void BlockFormattingContext::parent_context_did_dimension_child_root_box()
{
    m_was_notified_after_parent_dimensioned_my_root_box = true;

    // Left-side floats: offset_from_edge is from left edge (0) to left content edge of floating_box.
    for (auto& floating_box : m_left_floats.all_boxes) {
        floating_box->used_values.set_content_x(floating_box->offset_from_edge);
    }

    // Right-side floats: offset_from_edge is from right edge (float_containing_block_width) to the left content edge of floating_box.
    for (auto& floating_box : m_right_floats.all_boxes) {
        auto float_containing_block_width = containing_block_width_for(floating_box->box);
        floating_box->used_values.set_content_x(float_containing_block_width - floating_box->offset_from_edge);
    }

    layout_absolutely_positioned_children();
}

bool BlockFormattingContext::box_should_avoid_floats_because_it_establishes_fc(Box const& box)
{
    // https://drafts.csswg.org/css2/#floats
    // The border box of a table, a block-level replaced element, or an element in the normal flow that establishes
    // a new block formatting context (such as an element with 'overflow' other than 'visible') must not overlap the
    // margin box of any floats in the same block formatting context as the element itself. If necessary,
    // implementations should clear the said element by placing it below any preceding floats, but may place it
    // adjacent to such floats if there is sufficient space. They may even make the border box of said element
    // narrower than defined by section 10.3.3. CSS2 does not define when a UA may put said element next to the
    // float or by how much said element may become narrower.

    // https://drafts.csswg.org/css-flexbox/#flex-containers
    // A flex container establishes a new flex formatting context for its contents. This is the same as establishing
    // a block formatting context, except that flex layout is used instead of block layout. For example, floats do
    // not intrude into the flex container, and the flex container’s margins do not collapse with the margins of its
    // contents.

    // https://drafts.csswg.org/css-grid/#grid-containers
    // A grid container that is not a subgrid establishes an independent grid formatting context for its contents.
    // This is the same as establishing an independent block formatting context, except that grid layout is used
    // instead of block layout: floats do not intrude into the grid container, and the grid container’s margins do
    // not collapse with the margins of its contents.

    auto formatting_context_type = formatting_context_type_created_by_box(box);
    return formatting_context_type.has_value()
        && first_is_one_of(formatting_context_type.value(), Type::Block, Type::Flex, Type::Grid);
}

void BlockFormattingContext::compute_width(Box const& box, AvailableSpace const& available_space)
{
    auto remaining_available_space = available_space;

    // Certain formatting contexts do not allow float intrusions, so reduce the available space for them.
    if (available_space.width.is_definite() && box_should_avoid_floats_because_it_establishes_fc(box)) {
        auto intrusion = intrusion_by_floats_into_box(box, 0);
        auto remaining_width = available_space.width.to_px_or_zero() - intrusion.left - intrusion.right;
        remaining_available_space.width = AvailableSize::make_definite(remaining_width);
    }

    if (box_is_sized_as_replaced_element(box, available_space)) {
        compute_width_for_block_level_replaced_element_in_normal_flow(box, available_space);
        if (box.is_floating()) {
            // 10.3.6 Floating, replaced elements:
            // https://www.w3.org/TR/CSS22/visudet.html#float-replaced-width
            return;
        }
    }

    if (box.is_floating()) {
        // 10.3.5 Floating, non-replaced elements:
        // https://www.w3.org/TR/CSS22/visudet.html#float-width
        compute_width_for_floating_box(box, available_space);
        return;
    }

    auto const& computed_values = box.computed_values();
    auto available_width_px = available_space.width.to_px_or_zero();
    auto margin_left = computed_values.margin().left().resolved_or_auto(box, available_width_px);
    auto margin_right = computed_values.margin().right().resolved_or_auto(box, available_width_px);
    auto const padding_left = computed_values.padding().left().resolved_or_auto(box, available_width_px);
    auto const padding_right = computed_values.padding().right().resolved_or_auto(box, available_width_px);

    auto& box_state = m_state.get_mutable(box);
    box_state.margin_left = margin_left.to_px_or_zero(box);
    box_state.margin_right = margin_right.to_px_or_zero(box);
    box_state.border_left = computed_values.border_left().width;
    box_state.border_right = computed_values.border_right().width;
    box_state.padding_left = padding_left.to_px_or_zero(box);
    box_state.padding_right = padding_right.to_px_or_zero(box);

    // NOTE: If we are calculating the min-content or max-content width of this box,
    //       and the width should be treated as auto, then we can simply return here,
    //       as the preferred width and min/max constraints are irrelevant for intrinsic sizing.
    if (box_state.width_constraint != SizeConstraint::None)
        return;

    auto const remaining_width_px = remaining_available_space.width.to_px_or_zero();
    auto const zero_value = CSS::Length::make_px(0);

    auto try_compute_width = [&](CSS::LengthOrAuto const& a_width) {
        auto width = a_width;
        margin_left = computed_values.margin().left().resolved_or_auto(box, available_space.width.to_px_or_zero());
        margin_right = computed_values.margin().right().resolved_or_auto(box, available_space.width.to_px_or_zero());
        CSSPixels total_px = computed_values.border_left().width + computed_values.border_right().width;
        for (auto& value : { CSS::LengthOrAuto(margin_left), CSS::LengthOrAuto(padding_left), width, CSS::LengthOrAuto(padding_right), CSS::LengthOrAuto(margin_right) })
            total_px += value.to_px_or_zero(box);

        if (!box.is_inline()) {
            // 10.3.3 Block-level, non-replaced elements in normal flow
            // If 'width' is not 'auto' and 'border-left-width' + 'padding-left' + 'width' + 'padding-right' +
            // 'border-right-width' (plus any of 'margin-left' or 'margin-right' that are not 'auto') is larger than the
            // width of the containing block, then any 'auto' values for 'margin-left' or 'margin-right' are, for the
            // following rules, treated as zero.
            if (!width.is_auto() && total_px > remaining_width_px) {
                if (margin_left.is_auto())
                    margin_left = zero_value;
                if (margin_right.is_auto())
                    margin_right = zero_value;
            }

            // 10.3.3 cont'd.
            auto underflow_px = remaining_width_px - total_px;
            if (available_space.width.is_intrinsic_sizing_constraint())
                underflow_px = 0;

            if (width.is_auto()) {
                if (margin_left.is_auto())
                    margin_left = zero_value;
                if (margin_right.is_auto())
                    margin_right = zero_value;

                if (available_space.width.is_definite()) {
                    if (underflow_px >= 0) {
                        width = CSS::Length::make_px(underflow_px);
                    } else {
                        width = zero_value;
                    }
                } else if (available_space.width.is_min_content()) {
                    if (formatting_context_type_created_by_box(box).has_value())
                        width = CSS::Length::make_px(calculate_min_content_width(box));
                } else if (available_space.width.is_max_content()) {
                    if (formatting_context_type_created_by_box(box).has_value())
                        width = CSS::Length::make_px(calculate_max_content_width(box));
                } else {
                    VERIFY_NOT_REACHED();
                }
            } else {
                if (!margin_left.is_auto() && !margin_right.is_auto()) {
                    margin_right = CSS::Length::make_px(margin_right.to_px_or_zero(box) + underflow_px);
                } else if (!margin_left.is_auto() && margin_right.is_auto()) {
                    margin_right = CSS::Length::make_px(underflow_px);
                } else if (margin_left.is_auto() && !margin_right.is_auto()) {
                    margin_left = CSS::Length::make_px(underflow_px);
                } else { // margin_left.is_auto() && margin_right.is_auto()
                    auto half_of_the_underflow = CSS::Length::make_px(underflow_px / 2);
                    margin_left = half_of_the_underflow;
                    margin_right = half_of_the_underflow;
                }
            }
        }

        return width;
    };

    auto input_width = [&] -> CSS::LengthOrAuto {
        if (box_is_sized_as_replaced_element(box, available_space)) {
            // NOTE: Replaced elements had their width calculated independently above.
            //       We use that width as the input here to ensure that margins get resolved.
            return CSS::Length::make_px(box_state.content_width());
        }
        if (is<TableWrapper>(box))
            return CSS::Length::make_px(compute_table_box_width_inside_table_wrapper(box, remaining_available_space));

        // https://html.spec.whatwg.org/multipage/rendering.html#button-layout
        // If the computed value of 'inline-size' is 'auto', then the used value is the fit-content inline size.
        if (auto const* html_element = as_if<HTML::HTMLElement>(box.dom_node()); html_element
            && html_element->uses_button_layout() && computed_values.width().is_auto()) {
            return CSS::Length::make_px(calculate_fit_content_width(box, available_space));
        }

        if (should_treat_width_as_auto(box, available_space))
            return CSS::LengthOrAuto::make_auto();
        return CSS::Length::make_px(calculate_inner_width(box, available_space.width, computed_values.width()));
    }();

    // 1. The tentative used width is calculated (without 'min-width' and 'max-width')
    auto used_width = try_compute_width(input_width);

    // 2. The tentative used width is greater than 'max-width', the rules above are applied again,
    //    but this time using the computed value of 'max-width' as the computed value for 'width'.
    if (!should_treat_max_width_as_none(box, available_space.width)) {
        auto max_width = calculate_inner_width(box, available_space.width, computed_values.max_width());
        if (used_width.to_px_or_zero(box) > max_width)
            used_width = try_compute_width(CSS::Length::make_px(max_width));
    }

    // 3. If the resulting width is smaller than 'min-width', the rules above are applied again,
    //    but this time using the value of 'min-width' as the computed value for 'width'.
    if (!computed_values.min_width().is_auto()) {
        auto min_width = calculate_inner_width(box, available_space.width, computed_values.min_width());
        auto used_width_px = used_width.is_auto() ? remaining_available_space.width : AvailableSize::make_definite(used_width.to_px_or_zero(box));
        if (used_width_px < min_width)
            used_width = try_compute_width(CSS::Length::make_px(min_width));
    }

    if (!box_is_sized_as_replaced_element(box, available_space) && !used_width.is_auto())
        box_state.set_content_width(used_width.to_px_or_zero(box));

    box_state.margin_left = margin_left.to_px_or_zero(box);
    box_state.margin_right = margin_right.to_px_or_zero(box);
}

void BlockFormattingContext::avoid_float_intrusions(Box const& box, AvailableSpace const& available_space)
{
    if (box.computed_values().width().is_auto())
        return;
    if (!available_space.width.is_definite())
        return;
    if (!box_should_avoid_floats_because_it_establishes_fc(box))
        return;

    // https://drafts.csswg.org/css2/#floats
    // If necessary, implementations should clear the said element by placing it below any preceding floats, but may
    // place it adjacent to such floats if there is sufficient space.
    auto& box_state = m_state.get_mutable(box);
    while (true) {
        auto box_in_root_rect = margin_box_rect_in_ancestor_coordinate_space(box_state, root());
        auto space_used_by_floats = space_used_and_containing_margin_for_floats(box_in_root_rect.y());
        auto remaining_space = available_space.width.to_px_or_zero() - space_used_by_floats.left_used_space - space_used_by_floats.right_used_space;
        if (box_state.border_box_width() <= remaining_space)
            break;

        Optional<CSSPixels> topmost_float_bottom;
        auto find_topmost_float = [&](auto float_box) {
            if (!float_box)
                return;
            auto const& float_used_values = m_state.get(*float_box);
            auto float_in_root_rect = margin_box_rect_in_ancestor_coordinate_space(float_used_values, root());
            auto float_bottom = float_in_root_rect.bottom();
            if (!topmost_float_bottom.has_value() || topmost_float_bottom.value() > float_bottom)
                topmost_float_bottom = float_bottom;
        };
        find_topmost_float(space_used_by_floats.matching_left_float_box);
        find_topmost_float(space_used_by_floats.matching_right_float_box);
        if (!topmost_float_bottom.has_value())
            break;

        box_state.set_content_y(box_state.offset.y() + topmost_float_bottom.value() - box_in_root_rect.y());
    }
}

void BlockFormattingContext::compute_width_for_floating_box(Box const& box, AvailableSpace const& available_space)
{
    // 10.3.5 Floating, non-replaced elements
    auto& computed_values = box.computed_values();

    auto width_of_containing_block = available_space.width.to_px_or_zero();

    // If 'margin-left', or 'margin-right' are computed as 'auto', their used value is '0'.
    auto margin_left = computed_values.margin().left().to_px_or_zero(box, width_of_containing_block);
    auto margin_right = computed_values.margin().right().to_px_or_zero(box, width_of_containing_block);

    auto& box_state = m_state.get_mutable(box);
    box_state.padding_left = computed_values.padding().left().to_px_or_zero(box, width_of_containing_block);
    box_state.padding_right = computed_values.padding().right().to_px_or_zero(box, width_of_containing_block);
    box_state.margin_left = margin_left;
    box_state.margin_right = margin_right;
    box_state.border_left = computed_values.border_left().width;
    box_state.border_right = computed_values.border_right().width;

    auto compute_width = [&](CSS::LengthOrAuto width) {
        // If 'width' is computed as 'auto', the used value is the "shrink-to-fit" width.
        if (width.is_auto()) {
            auto result = calculate_shrink_to_fit_widths(box);

            if (available_space.width.is_definite()) {
                // Find the available width: in this case, this is the width of the containing
                // block minus the used values of 'margin-left', 'border-left-width', 'padding-left',
                // 'padding-right', 'border-right-width', 'margin-right', and the widths of any relevant scroll bars.
                auto available_width = available_space.width.to_px_or_zero()
                    - margin_left - computed_values.border_left().width - box_state.padding_left
                    - box_state.padding_right - computed_values.border_right().width - margin_right;
                // Then the shrink-to-fit width is: min(max(preferred minimum width, available width), preferred width).
                width = CSS::Length::make_px(min(max(result.preferred_minimum_width, available_width), result.preferred_width));
            } else if (available_space.width.is_indefinite() || available_space.width.is_max_content()) {
                // Fold the formula for shrink-to-fit width for indefinite and max-content available width.
                width = CSS::Length::make_px(result.preferred_width);
            } else {
                // Fold the formula for shrink-to-fit width for min-content available width.
                width = CSS::Length::make_px(min(result.preferred_minimum_width, result.preferred_width));
            }
        }

        return width;
    };

    auto input_width = [&] -> CSS::LengthOrAuto {
        if (should_treat_width_as_auto(box, available_space))
            return CSS::LengthOrAuto::make_auto();
        return CSS::Length::make_px(calculate_inner_width(box, available_space.width, computed_values.width()));
    }();

    // 1. The tentative used width is calculated (without 'min-width' and 'max-width')
    auto width = compute_width(input_width);

    // 2. The tentative used width is greater than 'max-width', the rules above are applied again,
    //    but this time using the computed value of 'max-width' as the computed value for 'width'.
    if (!should_treat_max_width_as_none(box, available_space.width)) {
        auto max_width = calculate_inner_width(box, available_space.width, computed_values.max_width());
        if (width.to_px_or_zero(box) > max_width)
            width = compute_width(CSS::Length::make_px(max_width));
    }

    // 3. If the resulting width is smaller than 'min-width', the rules above are applied again,
    //    but this time using the value of 'min-width' as the computed value for 'width'.
    if (!computed_values.min_width().is_auto()) {
        auto min_width = calculate_inner_width(box, available_space.width, computed_values.min_width());
        if (width.to_px_or_zero(box) < min_width)
            width = compute_width(CSS::Length::make_px(min_width));
    }

    box_state.set_content_width(width.to_px_or_zero(box));
}

void BlockFormattingContext::compute_width_for_block_level_replaced_element_in_normal_flow(Box const& box, AvailableSpace const& available_space)
{
    // 10.3.6 Floating, replaced elements
    auto& computed_values = box.computed_values();

    auto width_of_containing_block = available_space.width.to_px_or_zero();

    // 10.3.4 Block-level, replaced elements in normal flow
    // The used value of 'width' is determined as for inline replaced elements. Then the rules for
    // non-replaced block-level elements are applied to determine the margins.
    // If 'margin-left', or 'margin-right' are computed as 'auto', their used value is '0'.
    auto margin_left = computed_values.margin().left().to_px_or_zero(box, width_of_containing_block);
    auto margin_right = computed_values.margin().right().to_px_or_zero(box, width_of_containing_block);
    auto const padding_left = computed_values.padding().left().to_px_or_zero(box, width_of_containing_block);
    auto const padding_right = computed_values.padding().right().to_px_or_zero(box, width_of_containing_block);

    auto& box_state = m_state.get_mutable(box);
    auto width = compute_width_for_replaced_element(box, available_space);
    box_state.margin_left = margin_left;
    box_state.margin_right = margin_right;
    box_state.border_left = computed_values.border_left().width;
    box_state.border_right = computed_values.border_right().width;
    box_state.padding_left = padding_left;
    box_state.padding_right = padding_right;
    box_state.set_content_width(calculate_inner_width(box, available_space.width, CSS::Size::make_px(width)));
}

void BlockFormattingContext::resolve_used_height_if_not_treated_as_auto(Box const& box, AvailableSpace const& available_space)
{
    if (should_treat_height_as_auto(box, available_space)) {
        return;
    }

    auto const& computed_values = box.computed_values();
    auto& box_state = m_state.get_mutable(box);

    auto height = calculate_inner_height(box, available_space, box.computed_values().height());

    if (!should_treat_max_height_as_none(box, available_space.height)) {
        if (!computed_values.max_height().is_auto()) {
            auto max_height = calculate_inner_height(box, available_space, computed_values.max_height());
            height = min(height, max_height);
        }
    }
    if (!computed_values.min_height().is_auto()) {
        height = max(height, calculate_inner_height(box, available_space, computed_values.min_height()));
    }

    box_state.set_content_height(height);
    box_state.set_has_definite_height(true);
}

void BlockFormattingContext::resolve_used_height_if_treated_as_auto(Box const& box, AvailableSpace const& available_space, FormattingContext const* box_formatting_context)
{
    if (!should_treat_height_as_auto(box, available_space)) {
        return;
    }

    auto const& computed_values = box.computed_values();
    auto& box_state = m_state.get_mutable(box);

    CSSPixels height = 0;
    if (box_is_sized_as_replaced_element(box, available_space)) {
        height = compute_height_for_replaced_element(box, available_space);
    } else {
        if (box_formatting_context) {
            height = box_formatting_context->automatic_content_height();
        } else {
            height = compute_auto_height_for_block_level_element(box, m_state.get(box).available_inner_space_or_constraints_from(available_space));
        }
    }

    if (!should_treat_max_height_as_none(box, available_space.height)) {
        if (!computed_values.max_height().is_auto()) {
            auto max_height = calculate_inner_height(box, available_space, computed_values.max_height());
            height = min(height, max_height);
        }
    }
    if (!computed_values.min_height().is_auto()) {
        height = max(height, calculate_inner_height(box, available_space, computed_values.min_height()));
    }

    if (box.document().in_quirks_mode()
        && box.dom_node()
        && box.dom_node()->is_html_html_element()
        && box.computed_values().height().is_auto()) {
        // 3.6. The html element fills the viewport quirk
        // https://quirks.spec.whatwg.org/#the-html-element-fills-the-viewport-quirk
        // FIXME: Handle vertical writing mode.

        // 1. Let margins be sum of the used values of the margin-left and margin-right properties of element
        //    if element has a vertical writing mode, otherwise let margins be the sum of the used values of
        //    the margin-top and margin-bottom properties of element.
        auto margins = box_state.margin_top + box_state.margin_bottom;

        // 2. Let size be the size of the initial containing block in the block flow direction minus margins.
        auto size = box_state.containing_block_used_values()->content_height() - margins;

        // 3. Return the bigger value of size and the normal border box size the element would have
        //    according to the CSS specification.
        height = max(size, height);

        // NOTE: The height of the root element when affected by this quirk is considered to be definite.
        box_state.set_has_definite_height(true);
    }

    if (box.document().in_quirks_mode()
        && box.dom_node()
        && box.dom_node()->is_html_body_element()
        && box.computed_values().height().is_auto()) {
        // 3.7. The body element fills the html element quirk
        // https://quirks.spec.whatwg.org/#the-body-element-fills-the-html-element-quirk
        // FIXME: Handle vertical writing mode.

        // The element body must additionally meet the following conditions:
        // - The computed value of the 'position' property of element is neither 'absolute' nor 'fixed'.
        // - The computed value of the 'float' property of element is 'none'.
        // - Element is not an inline-level element.
        // - Element is not a multi-column spanning element.
        // NON-STANDARD: We don't check column-span since no browser actually excludes it.
        if (!box.is_absolutely_positioned() && !box.is_floating() && !box.is_inline()) {
            // 1. Let margins be sum of the used values of the margin-left and margin-right properties of element
            //    if element has a vertical writing mode, otherwise let margins be the sum of the used values of
            //    the margin-top and margin-bottom properties of element.
            auto margins = box_state.margin_top + box_state.margin_bottom;

            // 2. Let size be the size of element's parent element's content box in the block flow direction minus margins.
            auto size = box_state.containing_block_used_values()->content_height() - margins;

            // 3. Return the bigger value of size and the normal border box size the element would have
            //    according to the CSS specification.
            height = max(size, height);
        }
    }

    box_state.set_content_height(height);
}

void BlockFormattingContext::layout_inline_children(BlockContainer const& block_container, AvailableSpace const& available_space)
{
    VERIFY(block_container.children_are_inline());

    auto& block_container_state = m_state.get_mutable(block_container);

    InlineFormattingContext context(m_state, m_layout_mode, block_container, block_container_state, *this);
    context.run(available_space);

    if (!block_container_state.has_definite_width()) {
        // NOTE: min-width or max-width for boxes with inline children can only be applied after inside layout
        //       is done and width of box content is known
        auto used_width_px = context.automatic_content_width();
        // https://www.w3.org/TR/css-sizing-3/#sizing-values
        // Percentages are resolved against the width/height, as appropriate, of the box’s containing block.
        CSSPixels containing_block_width = 0;
        if (auto const* containing_block_used_values = m_state.try_get(*block_container.containing_block()))
            containing_block_width = containing_block_used_values->content_width();
        auto available_width = AvailableSize::make_definite(containing_block_width);
        if (!should_treat_max_width_as_none(block_container, available_space.width)) {
            auto max_width_px = calculate_inner_width(block_container, available_width, block_container.computed_values().max_width());
            if (used_width_px > max_width_px)
                used_width_px = max_width_px;
        }

        auto should_treat_min_width_as_auto = [&] {
            auto const& available_width = available_space.width;
            auto const& min_width = block_container.computed_values().min_width();
            if (min_width.is_auto())
                return true;
            if (min_width.is_fit_content() && available_width.is_intrinsic_sizing_constraint())
                return true;
            if (min_width.is_max_content() && available_width.is_max_content())
                return true;
            if (min_width.is_min_content() && available_width.is_min_content())
                return true;
            return false;
        }();
        if (!should_treat_min_width_as_auto) {
            auto min_width_px = calculate_inner_width(block_container, available_width, block_container.computed_values().min_width());
            if (used_width_px < min_width_px)
                used_width_px = min_width_px;
        }
        block_container_state.set_content_width(used_width_px);
        block_container_state.set_content_height(context.automatic_content_height());
    }
}

CSSPixels BlockFormattingContext::compute_auto_height_for_block_level_element(Box const& box, AvailableSpace const& available_space)
{
    if (creates_block_formatting_context(box)) {
        return compute_auto_height_for_block_formatting_context_root(box);
    }

    auto const& box_state = m_state.get(box);

    auto display = box.display();
    if (display.is_flex_inside()) {
        // https://drafts.csswg.org/css-flexbox-1/#algo-main-container
        // NOTE: The automatic block size of a block-level flex container is its max-content size.
        return calculate_max_content_height(box, available_space.width.to_px_or_zero());
    }
    if (display.is_grid_inside()) {
        // https://www.w3.org/TR/css-grid-2/#intrinsic-sizes
        // In both inline and block formatting contexts, the grid container’s auto block size is its
        // max-content size.
        return calculate_max_content_height(box, available_space.width.to_px_or_zero());
    }
    if (display.is_table_inside()) {
        return calculate_max_content_height(box, available_space.width.to_px_or_zero());
    }

    // https://www.w3.org/TR/CSS22/visudet.html#normal-block
    // 10.6.3 Block-level non-replaced elements in normal flow when 'overflow' computes to 'visible'

    // The element's height is the distance from its top content edge to the first applicable of the following:

    // 1. the bottom edge of the last line box, if the box establishes a inline formatting context with one or more lines
    if (box.children_are_inline() && !box_state.line_boxes.is_empty())
        return box_state.line_boxes.last().bottom();

    // 2. the bottom edge of the bottom (possibly collapsed) margin of its last in-flow child, if the child's bottom margin does not collapse with the element's bottom margin
    // 3. the bottom border edge of the last in-flow child whose top margin doesn't collapse with the element's bottom margin
    if (!box.children_are_inline()) {
        CSSPixels marker_line_height = 0;
        for (auto* child_box = box.last_child_of_type<Box>(); child_box; child_box = child_box->previous_sibling_of_type<Box>()) {
            if (child_box->is_absolutely_positioned() || child_box->is_floating())
                continue;

            // NOTE: Markers are not in-flow, but for list items that contain only floats (or are otherwise empty),
            //       the marker's line-height determines the list item's height. This ensures proper vertical stacking
            //       of list items and alignment with their floated content.
            if (child_box->is_list_item_marker_box()) {
                marker_line_height = child_box->computed_values().line_height();
                continue;
            }

            auto const& child_box_state = m_state.get(*child_box);

            if (margins_collapse_through(*child_box, m_state))
                continue;

            auto margin_bottom = m_margin_state.current_collapsed_margin();
            if (box_state.padding_bottom == 0 && box_state.border_bottom == 0) {
                m_margin_state.set_box_last_in_flow_child_margin_bottom_collapsed(true);
                margin_bottom = 0;
            }

            return max(CSSPixels(0), child_box_state.offset.y() + child_box_state.content_height() + child_box_state.border_box_bottom() + margin_bottom);
        }

        // If no in-flow children were found but there's a marker, use the marker's line-height.
        if (marker_line_height > 0)
            return marker_line_height;
    }

    // AD-HOC: Contenteditable elements must have a minimum height (line-height) when empty, to remain clickable and
    //         usable for text input, even though this is not specified.
    //         See: https://github.com/w3c/editing/issues/70.
    if (auto const* element = as_if<DOM::Element>(box.dom_node()); element && element->is_editing_host())
        return box.computed_values().line_height();

    // 4. zero, otherwise
    return 0;
}

static CSSPixels containing_block_height_to_resolve_percentage_in_quirks_mode(Box const& box, LayoutState const& state)
{
    auto content_height_of = [&](NodeWithStyleAndBoxModelMetrics const& node) -> CSSPixels {
        auto const* node_used_values = state.try_get(node);
        if (!node_used_values)
            return 0;
        return node_used_values->content_height();
    };

    // https://quirks.spec.whatwg.org/#the-percentage-height-calculation-quirk
    auto containing_block = box.containing_block();
    while (containing_block) {
        // 1. Let element be the nearest ancestor containing block of element, if there is one.
        //    Otherwise, return the initial containing block.
        if (containing_block->is_viewport()) {
            return content_height_of(*containing_block);
        }

        // 2. If element has a computed value of the display property that is table-cell, then return a
        //    UA-defined value.
        if (containing_block->display().is_table_cell()) {
            // FIXME: Likely UA-defined value should not be 0.
            return 0;
        }

        // 3. If element has a computed value of the height property that is not auto, then return element.
        if (!containing_block->computed_values().height().is_auto()) {
            return content_height_of(*containing_block);
        }

        // 4. If element has a computed value of the position property that is absolute, or if element is a
        //    not a block container or a table wrapper box, then return element.
        if (containing_block->is_absolutely_positioned() || !is<BlockContainer>(*containing_block) || is<TableWrapper>(*containing_block)) {
            return content_height_of(*containing_block);
        }

        // 5. Jump to the first step.
        containing_block = containing_block->containing_block();
    }
    VERIFY_NOT_REACHED();
}

void BlockFormattingContext::layout_block_level_box(Box const& box, BlockContainer const& block_container, CSSPixels& bottom_of_lowest_margin_box, AvailableSpace const& available_space)
{
    if (box.is_absolutely_positioned()) {
        if (m_layout_mode == LayoutMode::Normal) {
            auto& box_state = m_state.get_mutable(box);
            StaticPositionRect static_position;
            auto static_position_y = m_y_offset_of_current_block_container.value();
            // FIXME: This is a heuristic approximation. Ideally, originally-inline abspos
            //        elements would have their static position determined by the IFC that
            //        laid out the surrounding inline content, but our architecture currently
            //        routes all abspos elements through the BFC as block-level children.
            //        When the previous sibling is the anonymous wrapper that contains the
            //        inline content this element would have been part of, use that wrapper's
            //        y-offset as a rough approximation of the correct static position.
            if (box.display_before_box_type_transformation().is_inline_outside()) {
                if (auto const* sibling = as_if<NodeWithStyle>(box.previous_sibling());
                    sibling && sibling->is_anonymous() && sibling->children_are_inline())
                    static_position_y = m_state.get(*sibling).offset.y();
            }
            static_position.rect = { { 0, static_position_y }, { 0, 0 } };
            box_state.set_static_position_rect(static_position);
        }
        return;
    }

    auto& box_state = m_state.get_mutable(box);

    // NOTE: ListItemMarkerBoxes are placed by their corresponding ListItemBox.
    if (is<ListItemMarkerBox>(box))
        return;

    resolve_vertical_box_model_metrics(box, m_state.get(block_container).content_width());

    if (box.is_floating()) {
        auto const y = m_y_offset_of_current_block_container.value();
        auto margin_top = !m_margin_state.has_block_container_waiting_for_final_y_position() ? m_margin_state.current_collapsed_margin() : 0;
        layout_floating_box(box, block_container, available_space, margin_top + y);
        bottom_of_lowest_margin_box = max(bottom_of_lowest_margin_box, box_state.offset.y() + box_state.content_height() + box_state.margin_box_bottom());
        return;
    }

    m_margin_state.add_margin(box_state.margin_top);
    auto introduce_clearance = clear_floating_boxes(box, {});
    if (introduce_clearance == DidIntroduceClearance::Yes)
        m_margin_state.reset();
    m_margin_state.update_block_waiting_for_final_y_position();

    auto const y = m_y_offset_of_current_block_container.value();

    auto box_is_html_element_in_quirks_mode = box.document().in_quirks_mode()
        && box.dom_node()
        && box.dom_node()->is_html_html_element()
        && box.computed_values().height().is_auto();

    // NOTE: In quirks mode, the html element's height matches the viewport so it can be treated as definite
    if (box_state.has_definite_height() || box_is_html_element_in_quirks_mode)
        resolve_used_height_if_treated_as_auto(box, available_space);

    auto independent_formatting_context = create_independent_formatting_context_if_needed(m_state, m_layout_mode, box);

    // NOTE: It is possible to encounter SVGMaskBox nodes while doing layout of formatting context established by <foreignObject> with a mask.
    //       We should skip and let SVGFormattingContext take care of them.
    if (box.is_svg_mask_box())
        return;

    if (!independent_formatting_context && !is<BlockContainer>(box)) {
        dbgln("FIXME: Block-level box is not BlockContainer but does not create formatting context: {}", box.debug_description());
        return;
    }

    CSSPixels margin_top = m_margin_state.current_collapsed_margin();

    if (m_margin_state.has_block_container_waiting_for_final_y_position()) {
        // If first child margin top will collapse with margin-top of containing block then margin-top of child is 0
        margin_top = 0;
    }

    place_block_level_element_in_normal_flow_vertically(box, y + margin_top);

    compute_width(box, available_space);
    avoid_float_intrusions(box, available_space);

    place_block_level_element_in_normal_flow_horizontally(box, available_space);

    AvailableSpace available_space_for_height_resolution = available_space;
    auto is_table_box = box.display().is_table_row() || box.display().is_table_row_group() || box.display().is_table_header_group() || box.display().is_table_footer_group() || box.display().is_table_cell() || box.display().is_table_caption();
    // https://quirks.spec.whatwg.org/#the-percentage-height-calculation-quirk
    auto shadow_root = box.dom_node() ? box.dom_node()->containing_shadow_root() : nullptr;
    bool is_in_ua_internal_shadow_tree = shadow_root && shadow_root->is_user_agent_internal();
    if (box.document().in_quirks_mode() && box.computed_values().height().is_percentage() && !is_table_box && !is_in_ua_internal_shadow_tree) {
        // In quirks mode, for the purpose of calculating the height of an element, if the
        // computed value of the position property of element is relative or static, the specified value
        // for the height property of element is a <percentage>, and element does not have a computed
        // value of the display property that is table-row, table-row-group, table-header-group,
        // table-footer-group, table-cell or table-caption, the containing block of element must be
        // calculated using the following algorithm, aborting on the first step that returns a value:
        auto height = containing_block_height_to_resolve_percentage_in_quirks_mode(box, m_state);
        available_space_for_height_resolution.height = AvailableSize::make_definite(height);
    }

    resolve_used_height_if_not_treated_as_auto(box, available_space_for_height_resolution);

    // NOTE: Flex containers with `auto` height are treated as `max-content`, so we can compute their height early.
    if (box.has_auto_content_box_size() || box.display().is_flex_inside()) {
        resolve_used_height_if_treated_as_auto(box, available_space_for_height_resolution);
    }

    // This monster basically means: "a ListItemBox that does not have specified content in the ::marker pseudo-element".
    // This happens for ::marker with content 'normal'.
    // FIXME: We currently so not support ListItemBox-es generated by pseudo-elements. We will need to, eventually.
    auto const* li_box = as_if<ListItemBox>(box);
    auto is_list_item_box_without_css_content = li_box != nullptr;
    if (auto const* dom_node = as_if<DOM::Element>(box.dom_node()); li_box && dom_node) {
        if (auto const computed_properties = dom_node->computed_properties(CSS::PseudoElement::Marker))
            is_list_item_box_without_css_content = !computed_properties->property(CSS::PropertyID::Content).is_content();
    }

    // Before we insert the children of a list item we need to know the location of the marker.
    // If we do not do this then left-floating elements inside the list item will push the marker to the right,
    // in some cases even causing it to overlap with the non-floating content of the list.
    CSSPixels left_space_before_children_formatted;
    if (is_list_item_box_without_css_content && li_box->marker()) {
        // We need to ensure that our height and width are final before we calculate our left offset.
        // Otherwise, the y at which we calculate the intrusion by floats might be incorrect.
        ensure_sizes_correct_for_left_offset_calculation(*li_box);

        auto const& list_item_state = m_state.get(*li_box);
        auto const& marker_state = m_state.get(*li_box->marker());

        auto offset_y = max(CSSPixels(0), (li_box->marker()->computed_values().line_height() - marker_state.content_height()) / 2);
        auto space_used_before_children_formatted = intrusion_by_floats_into_box(list_item_state, offset_y);

        left_space_before_children_formatted = space_used_before_children_formatted.left;
    }

    if (independent_formatting_context) {
        // Margins of elements that establish new formatting contexts do not collapse with their in-flow children
        m_margin_state.reset();

        // This box establishes a new formatting context. Pass control to it.
        auto inner_available_space = box_state.available_inner_space_or_constraints_from(available_space);

        // For boxes with auto height but non-auto min-height, we need to determine if the content height is less than
        // min-height. If so, we run layout with min-height as the available height.
        if (should_treat_height_as_auto(box, available_space) && !box.computed_values().min_height().is_auto()) {
            LayoutState throwaway_state(box);
            // Populate the entire containing block chain: the throwaway BFC may encounter abspos
            // elements whose containing block is an ancestor above `box`. We stop when the source
            // state lacks an entry, which happens when it is itself a nested throwaway state.
            for (auto cb = box.containing_block(); cb; cb = cb->containing_block()) {
                if (!m_state.try_get(*cb))
                    break;
                throwaway_state.populate_node_from(m_state, *cb);
            }

            auto measuring_context = create_independent_formatting_context_if_needed(throwaway_state, m_layout_mode, box);
            measuring_context->run(inner_available_space);
            auto content_height = measuring_context->automatic_content_height();
            auto min_height = calculate_inner_height(box, available_space, box.computed_values().min_height());
            if (content_height < min_height) {
                inner_available_space.height = AvailableSize::make_definite(min_height);
            }
        }

        independent_formatting_context->run(inner_available_space);
    } else {
        // This box participates in the current block container's flow.
        auto space_available_for_children = box.is_anonymous() ? available_space : box_state.available_inner_space_or_constraints_from(available_space);
        if (box.children_are_inline()) {
            layout_inline_children(as<BlockContainer>(box), space_available_for_children);
        } else {
            auto registered_block_container_y_position_update_callback = false;
            if (box_state.border_top > 0 || box_state.padding_top > 0) {
                // margin-top of block container can't collapse with it's children if it has non zero border or padding
                m_margin_state.reset();
            } else if (!m_margin_state.has_block_container_waiting_for_final_y_position()) {
                // margin-top of block container can be updated during children layout hence it's final y position yet to be determined
                m_margin_state.register_block_container_y_position_update_callback([this, &box, y, introduce_clearance](CSSPixels margin_top) {
                    if (introduce_clearance == DidIntroduceClearance::No) {
                        place_block_level_element_in_normal_flow_vertically(box, margin_top + y);
                    }
                });
                registered_block_container_y_position_update_callback = true;
            }

            layout_block_level_children(as<BlockContainer>(box), space_available_for_children);

            if (registered_block_container_y_position_update_callback) {
                m_margin_state.unregister_block_container_y_position_update_callback();
            }
        }
    }

    // Tables already set their height during the independent formatting context run. When multi-line text cells are involved, using different
    // available space here than during the independent formatting context run can result in different line breaks and thus a different height.
    if (!box.display().is_table_inside()) {
        resolve_used_height_if_treated_as_auto(box, available_space_for_height_resolution, independent_formatting_context);
    }

    // Now that our children are formatted we place the ListItemBox with the left space we remembered.
    if (is_list_item_box_without_css_content)
        // The marker pseudo-element will be created from a ListItemMarkerBox
        layout_list_item_marker(*li_box, left_space_before_children_formatted);
    // Otherwise, it will be a dealt with as a generic pseudo-element with the content of the ::marker pseudo-element.

    if (independent_formatting_context || !margins_collapse_through(box, m_state)) {
        if (!m_margin_state.box_last_in_flow_child_margin_bottom_collapsed()) {
            m_margin_state.reset();
        }
        m_y_offset_of_current_block_container = box_state.offset.y() + box_state.content_height() + box_state.border_box_bottom();
    }
    m_margin_state.set_box_last_in_flow_child_margin_bottom_collapsed(false);

    m_margin_state.add_margin(box_state.margin_bottom);
    m_margin_state.update_block_waiting_for_final_y_position();

    auto const& block_container_state = m_state.get(block_container);
    compute_inset(box, content_box_rect(block_container_state).size());

    bottom_of_lowest_margin_box = max(bottom_of_lowest_margin_box, box_state.offset.y() + box_state.content_height() + box_state.margin_box_bottom());

    if (independent_formatting_context)
        independent_formatting_context->parent_context_did_dimension_child_root_box();
}

void BlockFormattingContext::layout_block_level_children(BlockContainer const& block_container, AvailableSpace const& available_space)
{
    VERIFY(!block_container.children_are_inline());

    CSSPixels bottom_of_lowest_margin_box = 0;

    TemporaryChange<Optional<CSSPixels>> change { m_y_offset_of_current_block_container, CSSPixels(0) };
    block_container.for_each_child_of_type<Box>([&](Box& box) {
        layout_block_level_box(box, block_container, bottom_of_lowest_margin_box, available_space);
        return IterationDecision::Continue;
    });

    if (m_layout_mode == LayoutMode::IntrinsicSizing) {
        auto& block_container_state = m_state.get_mutable(block_container);
        if (!block_container_state.has_definite_width()) {
            auto width = greatest_child_width(block_container);
            auto const& computed_values = block_container.computed_values();
            // NOTE: Min and max constraints are not applied to a box that is being sized as intrinsic because
            //       according to css-sizing-3 spec:
            //       The min-content size of a box in each axis is the size it would have if it was a float given an
            //       auto size in that axis (and no minimum or maximum size in that axis) and if its containing block
            //       was zero-sized in that axis.
            if (block_container_state.width_constraint == SizeConstraint::None) {
                if (!should_treat_max_width_as_none(block_container, available_space.width)) {
                    auto max_width = calculate_inner_width(block_container, available_space.width,
                        computed_values.max_width());
                    width = min(width, max_width);
                }
                if (!computed_values.min_width().is_auto()) {
                    auto min_width = calculate_inner_width(block_container, available_space.width,
                        computed_values.min_width());
                    width = max(width, min_width);
                }
            }
            block_container_state.set_content_width(width);
            block_container_state.set_content_height(bottom_of_lowest_margin_box);
        }
    }
}

// https://html.spec.whatwg.org/multipage/rendering.html#the-fieldset-and-legend-elements
void BlockFormattingContext::layout_fieldset_with_rendered_legend(FieldSetBox const& fieldset_box, AvailableSpace const& available_space)
{
    auto& fieldset_state = m_state.get_mutable(fieldset_box);

    auto legend = fieldset_box.rendered_legend();
    VERIFY(legend);

    // Lay out the legend to determine its dimensions.
    {
        TemporaryChange<Optional<CSSPixels>> change { m_y_offset_of_current_block_container, CSSPixels(0) };
        CSSPixels dummy_bottom = 0;
        layout_block_level_box(*legend, fieldset_box, dummy_bottom, available_space);
    }

    // If the computed value of 'inline-size' is 'auto', then the used value is the fit-content inline size.
    auto& legend_state = m_state.get_mutable(*legend);
    if (legend->computed_values().width().is_auto()) {
        auto width = calculate_fit_content_width(*legend, available_space);
        legend_state.set_content_width(width);
    }

    // The space allocated for the element's border on the block-start side is expected to be the element's
    // 'border-block-start-width' or the rendered legend's margin box size in the fieldset's block-flow direction,
    // whichever is greater.
    auto effective_border = max(fieldset_state.border_top, legend_state.margin_box_height());
    auto extra_top = effective_border - fieldset_state.border_top;

    // Lay out non-legend children below the legend accommodation.
    m_margin_state.reset();

    CSSPixels bottom_of_lowest_margin_box = 0;
    {
        TemporaryChange<Optional<CSSPixels>> change { m_y_offset_of_current_block_container, extra_top };
        fieldset_box.for_each_child_of_type<Box>([&](Box& child) {
            if (&child == legend)
                return IterationDecision::Continue;
            layout_block_level_box(child, fieldset_box, bottom_of_lowest_margin_box, available_space);
            return IterationDecision::Continue;
        });
    }

    if (m_layout_mode == LayoutMode::IntrinsicSizing && !fieldset_state.has_definite_width()) {
        auto width = greatest_child_width(fieldset_box);
        auto const& computed_values = fieldset_box.computed_values();
        if (fieldset_state.width_constraint == SizeConstraint::None) {
            if (!should_treat_max_width_as_none(fieldset_box, available_space.width)) {
                auto max_width = calculate_inner_width(fieldset_box, available_space.width, computed_values.max_width());
                width = min(width, max_width);
            }
            if (!computed_values.min_width().is_auto()) {
                auto min_width = calculate_inner_width(fieldset_box, available_space.width, computed_values.min_width());
                width = max(width, min_width);
            }
        }
        fieldset_state.set_content_width(width);
        fieldset_state.set_content_height(bottom_of_lowest_margin_box);
    }

    // The element is expected to be positioned in the block-flow direction such that its border box is centered over
    // the border on the block-start side of the fieldset element.
    // FIXME: Take writing modes into consideration.
    auto legend_border_box_centering_offset = (effective_border - legend_state.border_box_height()) / 2;
    auto fieldset_border_box_top_in_content = -(fieldset_state.border_top + fieldset_state.padding_top);
    auto legend_content_y = fieldset_border_box_top_in_content + legend_border_box_centering_offset + legend_state.border_box_top();
    legend_state.set_content_y(legend_content_y);
}

void BlockFormattingContext::resolve_vertical_box_model_metrics(Box const& box, CSSPixels width_of_containing_block)
{
    auto& box_state = m_state.get_mutable(box);
    auto const& computed_values = box.computed_values();

    box_state.margin_top = computed_values.margin().top().to_px_or_zero(box, width_of_containing_block);
    box_state.margin_bottom = computed_values.margin().bottom().to_px_or_zero(box, width_of_containing_block);
    box_state.border_top = computed_values.border_top().width;
    box_state.border_bottom = computed_values.border_bottom().width;
    box_state.padding_top = computed_values.padding().top().to_px_or_zero(box, width_of_containing_block);
    box_state.padding_bottom = computed_values.padding().bottom().to_px_or_zero(box, width_of_containing_block);
}

void BlockFormattingContext::resolve_horizontal_box_model_metrics(Box const& box, CSSPixels width_of_containing_block)
{
    auto& box_state = m_state.get_mutable(box);
    auto const& computed_values = box.computed_values();

    box_state.margin_left = computed_values.margin().left().to_px_or_zero(box, width_of_containing_block);
    box_state.margin_right = computed_values.margin().right().to_px_or_zero(box, width_of_containing_block);
    box_state.border_left = computed_values.border_left().width;
    box_state.border_right = computed_values.border_right().width;
    box_state.padding_left = computed_values.padding().left().to_px_or_zero(box, width_of_containing_block);
    box_state.padding_right = computed_values.padding().right().to_px_or_zero(box, width_of_containing_block);
}

BlockFormattingContext::DidIntroduceClearance BlockFormattingContext::clear_floating_boxes(Node const& child_box, Optional<InlineFormattingContext&> inline_formatting_context)
{
    auto const& computed_values = child_box.computed_values();
    auto result = DidIntroduceClearance::No;

    auto clear_floating_boxes = [&](FloatSideData& float_side) {
        if (float_side.current_boxes.is_empty())
            return;

        // NOTE: Floating boxes are globally relevant within this BFC, *but* their offset coordinates
        //       are relative to their containing block.
        //       This means that we have to first convert to a root-space Y coordinate before clearing,
        //       and then convert back to a local Y coordinate when assigning the cleared offset to
        //       the `child_box` layout state.

        // First, find the lowest margin box edge on this float side and calculate the Y offset just below it.
        // NOTE: We must look at all_boxes here, not current_boxes, because current_boxes gets cleared
        //       when floats are stacked (e.g. multiple width:100% floats). The clear property needs to
        //       clear past ALL preceding floats, not just the ones on the current "float line".
        CSSPixels clearance_y_in_root = 0;
        for (auto const& floating_box : float_side.all_boxes)
            clearance_y_in_root = max(clearance_y_in_root, floating_box->margin_box_rect_in_root_coordinate_space.bottom());

        // Then, convert the clearance Y to a coordinate relative to the containing block of `child_box`.
        CSSPixels clearance_y_in_containing_block = clearance_y_in_root;
        for (auto containing_block = child_box.containing_block(); containing_block && containing_block != &root(); containing_block = containing_block->containing_block())
            clearance_y_in_containing_block -= m_state.get(*containing_block).offset.y();

        if (inline_formatting_context.has_value()) {
            if (clearance_y_in_containing_block > inline_formatting_context->vertical_float_clearance()) {
                result = DidIntroduceClearance::Yes;
                inline_formatting_context->set_vertical_float_clearance(clearance_y_in_containing_block);
            }
        } else if (clearance_y_in_containing_block > m_y_offset_of_current_block_container.value()) {
            result = DidIntroduceClearance::Yes;
            m_y_offset_of_current_block_container = clearance_y_in_containing_block;
        }

        if (!child_box.is_floating())
            float_side.clear();
    };

    // FIXME: Honor writing-mode, direction and text-orientation.
    if (first_is_one_of(computed_values.clear(), CSS::Clear::Left, CSS::Clear::Both, CSS::Clear::InlineStart))
        clear_floating_boxes(m_left_floats);
    if (first_is_one_of(computed_values.clear(), CSS::Clear::Right, CSS::Clear::Both, CSS::Clear::InlineEnd))
        clear_floating_boxes(m_right_floats);

    return result;
}

void BlockFormattingContext::place_block_level_element_in_normal_flow_vertically(Box const& child_box, CSSPixels y)
{
    auto& box_state = m_state.get_mutable(child_box);
    y += box_state.border_box_top();
    box_state.set_content_y(y);

    for (auto const& float_box : m_left_floats.all_boxes)
        float_box->margin_box_rect_in_root_coordinate_space = margin_box_rect_in_ancestor_coordinate_space(float_box->used_values, root());
    for (auto const& float_box : m_right_floats.all_boxes)
        float_box->margin_box_rect_in_root_coordinate_space = margin_box_rect_in_ancestor_coordinate_space(float_box->used_values, root());
}

void BlockFormattingContext::place_block_level_element_in_normal_flow_horizontally(Box const& child_box, AvailableSpace const& available_space)
{
    auto& box_state = m_state.get_mutable(child_box);

    CSSPixels x = 0;
    CSSPixels available_width_within_containing_block = available_space.width.to_px_or_zero();

    if ((!m_left_floats.current_boxes.is_empty() || !m_right_floats.current_boxes.is_empty())
        && box_should_avoid_floats_because_it_establishes_fc(child_box)) {
        auto box_in_root_rect = margin_box_rect_in_ancestor_coordinate_space(box_state, root());
        auto space_and_containing_margin = space_used_and_containing_margin_for_floats(box_in_root_rect.y());
        available_width_within_containing_block -= space_and_containing_margin.left_used_space + space_and_containing_margin.right_used_space;

        // Since this box has a FC, it should avoid floats which means we cannot have its border box overlap with any
        // float's margin box. We start off at the right-most border of the floats, and if this box' margin-left is not
        // auto, we must overlap that margin with the floats as far as possible.
        x = space_and_containing_margin.left_used_space;
        if (!child_box.computed_values().margin().left().is_auto())
            x = max(x - max(box_state.margin_left, 0), 0);

        // All non-anonymous containing blocks that are ancestors of the child box, but are not ancestors of the left
        // float box, might have left margins set that overlap with the used float space.
        if (space_and_containing_margin.matching_left_float_box) {
            Box const* current_ancestor = child_box.non_anonymous_containing_block();
            while (!current_ancestor->is_ancestor_of(*space_and_containing_margin.matching_left_float_box)) {
                x -= m_state.get(*current_ancestor).margin_left;
                current_ancestor = current_ancestor->non_anonymous_containing_block();
            }
            x = max(x, 0);
        }
    }

    if (child_box.containing_block()->computed_values().text_align() == CSS::TextAlign::LibwebCenter) {
        x += (available_width_within_containing_block / 2) - box_state.content_width() / 2;
    } else if (child_box.containing_block()->computed_values().text_align() == CSS::TextAlign::LibwebRight) {
        // Subtracting the left margin here because left and right margins need to be swapped when aligning to the right
        x += available_width_within_containing_block - box_state.content_width() - box_state.margin_box_left();
    } else {
        x += box_state.margin_box_left();
    }

    box_state.set_content_x(x);
}

void BlockFormattingContext::layout_floating_box(Box const& box, BlockContainer const& block_container, AvailableSpace const& available_space, CSSPixels y, LineBuilder* line_builder)
{
    VERIFY(box.is_floating());

    auto& box_state = m_state.get_mutable(box);
    auto const& computed_values = box.computed_values();

    auto const& block_container_state = m_state.get(block_container);
    resolve_vertical_box_model_metrics(box, block_container_state.content_width());

    compute_width(box, available_space);

    resolve_used_height_if_not_treated_as_auto(box, available_space);

    // NOTE: Flex containers with `auto` height are treated as `max-content`, so we can compute their height early.
    if (box.has_auto_content_box_size() || box.display().is_flex_inside()) {
        resolve_used_height_if_treated_as_auto(box, available_space);
    }

    auto independent_formatting_context = layout_inside(box, m_layout_mode, box_state.available_inner_space_or_constraints_from(available_space));
    resolve_used_height_if_treated_as_auto(box, available_space, independent_formatting_context);

    // First we place the box normally (to get the right y coordinate.)
    // If we have a LineBuilder, we're in the middle of inline layout, otherwise this is block layout.
    if (line_builder) {
        auto y = line_builder->y_for_float_to_be_inserted_here(box);
        box_state.set_content_y(y + box_state.margin_box_top());
    } else {
        place_block_level_element_in_normal_flow_vertically(box, y + box_state.margin_top);
        place_block_level_element_in_normal_flow_horizontally(box, available_space);
    }

    // Then we float it to the left or right.
    // FIXME: This algorithm is fundamentally flawed. It tracks left and right floats independently,
    //        then patches up cross-side interactions after the fact. A better approach would be to
    //        find the first Y position where the float fits considering ALL existing floats on both
    //        sides in a single unified pass.
    auto float_box = [&](FloatSide side, FloatSideData& side_data) {
        CSSPixels offset_from_edge = 0;
        auto float_to_edge = [&] {
            if (side == FloatSide::Left)
                offset_from_edge = box_state.margin_box_left();
            else
                offset_from_edge = box_state.content_width() + box_state.margin_box_right();
        };

        auto box_in_root_rect = margin_box_rect_in_ancestor_coordinate_space(box_state, root());
        auto const initial_box_margin_y_in_root = box_in_root_rect.y();
        CSSPixels y_in_root = box_in_root_rect.y();
        CSSPixels y = box_state.offset.y();

        auto has_clearance = false;
        if (side == FloatSide::Left) {
            has_clearance = computed_values.clear() == CSS::Clear::Left || computed_values.clear() == CSS::Clear::Both;
        } else if (side == FloatSide::Right) {
            has_clearance = computed_values.clear() == CSS::Clear::Right || computed_values.clear() == CSS::Clear::Both;
        }

        if (side_data.current_boxes.is_empty()) {
            // This is the first floating box on this side. Go all the way to the edge.
            float_to_edge();
            side_data.y_offset = 0;
        } else {

            // NOTE: If we're in inline layout, the LineBuilder has already provided the right Y offset.
            //       In block layout, we adjust by the side's current Y offset here.
            if (!line_builder)
                y_in_root += side_data.y_offset;

            bool did_touch_preceding_float = false;
            bool did_place_next_to_preceding_float = false;

            // Walk all currently tracked floats on the side we're floating towards.
            // We're looking for the innermost preceding float that intersects vertically with `box`.
            for (auto& preceding_float : side_data.current_boxes.in_reverse()) {
                if (!preceding_float.margin_box_rect_in_root_coordinate_space.contains_vertically(y_in_root))
                    continue;
                // We found a preceding float that intersects vertically with the current float.
                // Now we need to find out if there's enough inline-axis space to stack them next to each other.
                CSSPixels tentative_offset_from_edge = 0;
                bool fits_next_to_preceding_float = false;
                if (side == FloatSide::Left) {
                    tentative_offset_from_edge = max(preceding_float.offset_from_edge + preceding_float.used_values.content_width() + preceding_float.used_values.margin_box_right(), 0) + box_state.margin_box_left();
                    if (available_space.width.is_definite()) {
                        fits_next_to_preceding_float = (tentative_offset_from_edge + box_state.content_width() + box_state.margin_box_right()) <= available_space.width.to_px_or_zero();
                    } else if (available_space.width.is_max_content() || available_space.width.is_indefinite()) {
                        fits_next_to_preceding_float = true;
                    }
                } else {
                    tentative_offset_from_edge = preceding_float.offset_from_edge + preceding_float.used_values.margin_box_left() + box_state.margin_box_right() + box_state.content_width();
                    if (available_space.width.is_definite()) {
                        fits_next_to_preceding_float = (tentative_offset_from_edge + box_state.margin_box_left()) <= available_space.width.to_px_or_zero();
                    } else if (available_space.width.is_max_content() || available_space.width.is_indefinite()) {
                        fits_next_to_preceding_float = true;
                    }
                }
                did_touch_preceding_float = true;
                if (!fits_next_to_preceding_float)
                    break;
                offset_from_edge = tentative_offset_from_edge;
                did_place_next_to_preceding_float = true;
                break;
            }

            if (!did_touch_preceding_float || !did_place_next_to_preceding_float || has_clearance) {
                // One of three things happened:
                // - This box does not touch another floating box.
                // - We ran out of horizontal space on this "float line", and need to break.
                // - This box has clearance.
                // Either way, we float this box all the way to the edge.
                float_to_edge();
                CSSPixels lowest_margin_edge = 0;
                for (auto const& current : side_data.current_boxes) {
                    auto current_rect = margin_box_rect_in_ancestor_coordinate_space(current.used_values, root());
                    lowest_margin_edge = max(lowest_margin_edge, current_rect.bottom());
                }

                side_data.y_offset += max<CSSPixels>(0, lowest_margin_edge - y_in_root);

                // Also, forget all previous boxes floated to this side while since they're no longer relevant.
                side_data.clear();
            }
        }

        // NOTE: If we're in inline layout, the LineBuilder has already provided the right Y offset.
        //       In block layout, we adjust by the side's current Y offset here.
        // FIXME: It's annoying that we have different behavior for inline vs block here.
        //        Find a way to unify the behavior so we don't need to branch here.
        if (!line_builder)
            y += side_data.y_offset;

        // NOTE: We don't set the X position here, that happens later, once we know the root block width.
        //       See parent_context_did_dimension_child_root_box() for that logic.
        box_state.set_content_y(y);

        // CSS2 9.5.1: "If there is not enough horizontal room for the float, it is shifted downward
        //              until either it fits or there are no more floats present."
        // After same-side stacking, check if the float fits horizontally considering opposite-side
        // floats. If not, push it below the shallowest blocking float and retry.
        if (!line_builder && available_space.width.is_definite()) {
            auto position_with_same_side_floats_after_lowering = [&](CSSPixels candidate_box_margin_y_in_root) {
                while (true) {
                    Vector<FloatingBox&> candidate_current_boxes;
                    CSSPixels lowest_margin_edge = candidate_box_margin_y_in_root;
                    for (auto const& existing_float : side_data.all_boxes) {
                        if (!existing_float->margin_box_rect_in_root_coordinate_space.contains_vertically(candidate_box_margin_y_in_root))
                            continue;
                        candidate_current_boxes.append(*existing_float);
                        lowest_margin_edge = max(lowest_margin_edge, existing_float->margin_box_rect_in_root_coordinate_space.bottom());
                    }

                    CSSPixels candidate_offset_from_edge = 0;
                    if (side == FloatSide::Left)
                        candidate_offset_from_edge = box_state.margin_box_left();
                    else
                        candidate_offset_from_edge = box_state.content_width() + box_state.margin_box_right();

                    bool did_touch_preceding_float = false;
                    bool did_place_next_to_preceding_float = false;
                    for (auto& preceding_float : candidate_current_boxes.in_reverse()) {
                        CSSPixels tentative_offset_from_edge = 0;
                        bool fits_next_to_preceding_float = false;
                        if (side == FloatSide::Left) {
                            tentative_offset_from_edge = max(preceding_float.offset_from_edge + preceding_float.used_values.content_width() + preceding_float.used_values.margin_box_right(), 0) + box_state.margin_box_left();
                            fits_next_to_preceding_float = (tentative_offset_from_edge + box_state.content_width() + box_state.margin_box_right()) <= available_space.width.to_px_or_zero();
                        } else {
                            tentative_offset_from_edge = preceding_float.offset_from_edge + preceding_float.used_values.margin_box_left() + box_state.margin_box_right() + box_state.content_width();
                            fits_next_to_preceding_float = (tentative_offset_from_edge + box_state.margin_box_left()) <= available_space.width.to_px_or_zero();
                        }

                        did_touch_preceding_float = true;
                        if (!fits_next_to_preceding_float)
                            break;
                        candidate_offset_from_edge = tentative_offset_from_edge;
                        did_place_next_to_preceding_float = true;
                        break;
                    }

                    if ((has_clearance && !candidate_current_boxes.is_empty()) || (did_touch_preceding_float && !did_place_next_to_preceding_float)) {
                        candidate_box_margin_y_in_root = lowest_margin_edge;
                        continue;
                    }

                    side_data.current_boxes.clear();
                    for (auto& current_float : candidate_current_boxes)
                        side_data.current_boxes.append(current_float);

                    side_data.y_offset = max<CSSPixels>(0, candidate_box_margin_y_in_root - initial_box_margin_y_in_root);
                    offset_from_edge = candidate_offset_from_edge;
                    auto box_in_root_rect = margin_box_rect_in_ancestor_coordinate_space(box_state, root());
                    y = box_state.offset.y() + candidate_box_margin_y_in_root - box_in_root_rect.y();
                    box_state.set_content_y(y);
                    break;
                }
            };

            while (true) {
                auto box_in_root_rect = margin_box_rect_in_ancestor_coordinate_space(box_state, root());
                auto space_used_by_floats = space_used_and_containing_margin_for_floats(box_in_root_rect.y());
                auto const* containing_block = box_state.containing_block_used_values();
                VERIFY(containing_block);
                auto current_containing_block_in_root_rect = content_box_rect_in_ancestor_coordinate_space(*containing_block, root());
                auto used_by_this_side = (side == FloatSide::Left)
                    ? offset_from_edge + box_state.content_width() + box_state.margin_box_right()
                    : offset_from_edge + box_state.margin_box_left();
                auto used_by_opposite_side = (side == FloatSide::Left)
                    ? max<CSSPixels>(0, space_used_by_floats.right_used_space + space_used_by_floats.right_total_containing_margin - (m_state.get(root()).content_width() - current_containing_block_in_root_rect.right()))
                    : max<CSSPixels>(0, space_used_by_floats.left_total_containing_margin + space_used_by_floats.left_used_space - current_containing_block_in_root_rect.x());
                if (used_by_this_side + used_by_opposite_side <= available_space.width.to_px_or_zero())
                    break;

                // Find the shallowest (topmost) opposite-side float blocking us and move below it.
                auto opposite_float_box = (side == FloatSide::Left)
                    ? space_used_by_floats.matching_right_float_box
                    : space_used_by_floats.matching_left_float_box;
                if (!opposite_float_box)
                    break;
                auto const& opposite_float_used_values = m_state.get(*opposite_float_box);
                auto opposite_float_bottom = margin_box_rect_in_ancestor_coordinate_space(opposite_float_used_values, root()).bottom();
                position_with_same_side_floats_after_lowering(opposite_float_bottom);
            }
        }

        auto top_margin_edge = y - box_state.margin_box_top();
        side_data.all_boxes.append(adopt_own(*new FloatingBox {
            .box = box,
            .used_values = box_state,
            .offset_from_edge = offset_from_edge,
            .top_margin_edge = top_margin_edge,
            .bottom_margin_edge = y + box_state.content_height() + box_state.margin_box_bottom(),
            .margin_box_rect_in_root_coordinate_space = margin_box_rect_in_ancestor_coordinate_space(box_state, root()),
        }));
        side_data.current_boxes.append(*side_data.all_boxes.last());
        m_last_inserted_float = *side_data.all_boxes.last();

        if (side == FloatSide::Left) {
            side_data.current_width = offset_from_edge + box_state.content_width() + box_state.margin_box_right();
        } else {
            side_data.current_width = offset_from_edge + box_state.margin_box_left();
        }
        side_data.max_width = max(side_data.current_width, side_data.max_width);
    };

    // Next, float to the left and/or right
    // FIXME: Honor writing-mode, direction and text-orientation.
    if (box.computed_values().float_() == CSS::Float::Left || box.computed_values().float_() == CSS::Float::InlineStart) {
        float_box(FloatSide::Left, m_left_floats);
    } else if (box.computed_values().float_() == CSS::Float::Right || box.computed_values().float_() == CSS::Float::InlineEnd) {
        float_box(FloatSide::Right, m_right_floats);
    }

    m_state.get_mutable(root()).add_floating_descendant(box);

    if (line_builder)
        line_builder->recalculate_available_space();

    compute_inset(box, content_box_rect(block_container_state).size());

    if (independent_formatting_context)
        independent_formatting_context->parent_context_did_dimension_child_root_box();
}

void BlockFormattingContext::ensure_sizes_correct_for_left_offset_calculation(ListItemBox const& list_item_box)
{
    if (!list_item_box.marker())
        return;

    auto& marker = *list_item_box.marker();
    auto& marker_state = m_state.get_mutable(marker);

    // If an image is used, the marker's dimensions are the same as the image.
    if (auto const* list_style_image = marker.list_style_image()) {
        marker_state.set_content_width(list_style_image->natural_width().value_or(0));
        marker_state.set_content_height(list_style_image->natural_height().value_or(0));
        return;
    }

    CSSPixels marker_size = marker.relative_size();
    marker_state.set_content_height(marker_size);

    // Text markers use text metrics to determine their width; other markers use square dimensions.
    auto const& marker_font = marker.first_available_font();
    auto marker_text = marker.text();
    if (marker_text.has_value()) {
        // FIXME: Use per-code-point fonts to measure text.
        auto text_width = marker_font.width(Utf16String::from_utf8(marker_text.value()));
        marker_state.set_content_width(CSSPixels::nearest_value_for(text_width));
    } else {
        marker_state.set_content_width(marker_size);
    }
}

void BlockFormattingContext::layout_list_item_marker(ListItemBox const& list_item_box, CSSPixels const& left_space_before_list_item_elements_formatted)
{
    if (!list_item_box.marker())
        return;

    auto& marker = *list_item_box.marker();
    auto& marker_state = m_state.get_mutable(marker);
    auto& list_item_state = m_state.get_mutable(list_item_box);

    auto marker_text = marker.text();

    // Text markers fit snug against the list item; non-text position themselves at 50% of the font size.
    CSSPixels marker_distance = 0;
    if (!marker_text.has_value())
        marker_distance = CSSPixels::nearest_value_for(.5f * marker.first_available_font().pixel_size());

    auto marker_height = marker_state.content_height();
    auto marker_width = marker_state.content_width();

    if (marker.list_style_position() == CSS::ListStylePosition::Inside) {
        list_item_state.set_content_x(list_item_state.offset.x() + marker_width + marker_distance);
        list_item_state.set_content_width(list_item_state.content_width() - marker_width);
    }

    auto offset_x = round(left_space_before_list_item_elements_formatted - marker_distance - marker_width);
    auto offset_y = round(max(CSSPixels(0), (marker.computed_values().line_height() - marker_height) / 2));
    marker_state.set_content_offset({ offset_x, offset_y });

    if (marker.computed_values().line_height() > list_item_state.content_height())
        list_item_state.set_content_height(marker.computed_values().line_height());
}

BlockFormattingContext::SpaceUsedAndContainingMarginForFloats BlockFormattingContext::space_used_and_containing_margin_for_floats(CSSPixels y) const
{
    SpaceUsedAndContainingMarginForFloats space_and_containing_margin;

    for (auto const& floating_box_ptr : m_left_floats.all_boxes.in_reverse()) {
        auto const& floating_box = *floating_box_ptr;
        // NOTE: The floating box is *not* in the final horizontal position yet, but the size and vertical position is valid.
        auto rect = floating_box.margin_box_rect_in_root_coordinate_space;
        if (rect.contains_vertically(y)) {
            CSSPixels offset_from_containing_block_chain_margins_between_here_and_root = 0;
            for (auto const* containing_block = floating_box.used_values.containing_block_used_values(); containing_block && &containing_block->node() != &root(); containing_block = containing_block->containing_block_used_values()) {
                offset_from_containing_block_chain_margins_between_here_and_root += containing_block->margin_box_left();
            }
            space_and_containing_margin.left_used_space = floating_box.offset_from_edge
                + floating_box.used_values.content_width()
                + floating_box.used_values.margin_box_right();
            space_and_containing_margin.left_total_containing_margin = offset_from_containing_block_chain_margins_between_here_and_root;
            space_and_containing_margin.matching_left_float_box = floating_box.box;
            break;
        }
    }

    for (auto const& floating_box_ptr : m_right_floats.all_boxes.in_reverse()) {
        auto const& floating_box = *floating_box_ptr;
        // NOTE: The floating box is *not* in the final horizontal position yet, but the size and vertical position is valid.
        auto rect = floating_box.margin_box_rect_in_root_coordinate_space;
        if (rect.contains_vertically(y)) {
            CSSPixels offset_from_containing_block_chain_margins_between_here_and_root = 0;
            for (auto const* containing_block = floating_box.used_values.containing_block_used_values(); containing_block && &containing_block->node() != &root(); containing_block = containing_block->containing_block_used_values()) {
                offset_from_containing_block_chain_margins_between_here_and_root += containing_block->margin_box_right();
            }
            space_and_containing_margin.right_used_space = floating_box.offset_from_edge
                + floating_box.used_values.margin_box_left();
            space_and_containing_margin.right_total_containing_margin = offset_from_containing_block_chain_margins_between_here_and_root;
            space_and_containing_margin.matching_right_float_box = floating_box.box;
            break;
        }
    }

    return space_and_containing_margin;
}

FormattingContext::SpaceUsedByFloats BlockFormattingContext::intrusion_by_floats_into_box(Box const& box, CSSPixels y_in_box) const
{
    return intrusion_by_floats_into_box(m_state.get(box), y_in_box);
}

FormattingContext::SpaceUsedByFloats BlockFormattingContext::intrusion_by_floats_into_box(LayoutState::UsedValues const& box_used_values, CSSPixels y_in_box) const
{
    // NOTE: Floats are relative to the BFC root box, not necessarily the containing block of this IFC.
    auto box_in_root_rect = content_box_rect_in_ancestor_coordinate_space(box_used_values, root());
    CSSPixels y_in_root = box_in_root_rect.y() + y_in_box;
    auto space_and_containing_margin = space_used_and_containing_margin_for_floats(y_in_root);

    CSSPixels left_intrusion = 0;
    if (space_and_containing_margin.matching_left_float_box) {
        auto left_side_floats_limit_to_right = space_and_containing_margin.left_total_containing_margin + space_and_containing_margin.left_used_space;
        left_intrusion = max(CSSPixels(0), left_side_floats_limit_to_right - box_in_root_rect.x());
    }

    // If we did not match a right float, the right_total_containing_margin will be 0 (as its never set). Since no floats means
    // no intrusion we would instead want it to be exactly equal to offset_from_containing_block_chain_margins_between_here_and_root.
    // Since this is not the case we have to explicitly handle this case.
    CSSPixels right_intrusion = 0;
    if (space_and_containing_margin.matching_right_float_box) {
        auto right_side_floats_limit_to_right = space_and_containing_margin.right_used_space + space_and_containing_margin.right_total_containing_margin;
        CSSPixels offset_from_containing_block_chain_margins_between_here_and_root = 0;
        for (auto const* containing_block = &box_used_values; containing_block && &containing_block->node() != &root(); containing_block = containing_block->containing_block_used_values()) {
            offset_from_containing_block_chain_margins_between_here_and_root += containing_block->margin_box_right();
        }
        right_intrusion = max(CSSPixels(0), right_side_floats_limit_to_right - offset_from_containing_block_chain_margins_between_here_and_root);
    }

    return { left_intrusion, right_intrusion };
}

CSSPixels BlockFormattingContext::greatest_child_width(Box const& box) const
{
    // Similar to FormattingContext::greatest_child_width()
    // but this one takes floats into account!
    CSSPixels max_width = m_left_floats.max_width + m_right_floats.max_width;
    if (box.children_are_inline()) {
        for (auto const& line_box : m_state.get(as<BlockContainer>(box)).line_boxes) {
            auto width_here = line_box_physical_width(box, line_box);
            auto line_top = line_box.bottom() - line_box.height();
            auto line_bottom = line_box.bottom();
            CSSPixels extra_width_from_left_floats = 0;
            for (auto& left_float : m_left_floats.all_boxes) {
                // NOTE: Floats directly affect the automatic size of their containing block, but only indirectly anything above in the tree.
                if (left_float->box->containing_block() != &box)
                    continue;
                if (line_top < left_float->bottom_margin_edge && line_bottom > left_float->top_margin_edge) {
                    extra_width_from_left_floats = max(extra_width_from_left_floats, left_float->offset_from_edge + left_float->used_values.content_width() + left_float->used_values.margin_box_right());
                }
            }
            CSSPixels extra_width_from_right_floats = 0;
            for (auto& right_float : m_right_floats.all_boxes) {
                // NOTE: Floats directly affect the automatic size of their containing block, but only indirectly anything above in the tree.
                if (right_float->box->containing_block() != &box)
                    continue;
                if (line_top < right_float->bottom_margin_edge && line_bottom > right_float->top_margin_edge) {
                    extra_width_from_right_floats = max(extra_width_from_right_floats, right_float->offset_from_edge + right_float->used_values.margin_box_left());
                }
            }
            width_here += extra_width_from_left_floats + extra_width_from_right_floats;
            max_width = max(max_width, width_here);
        }
    } else {
        box.for_each_child_of_type<Box>([&](Box const& child) {
            if (!child.is_absolutely_positioned())
                max_width = max(max_width, m_state.get(child).margin_box_width());
            return IterationDecision::Continue;
        });
    }
    return max_width;
}

// https://drafts.csswg.org/css-multicol/#pseudo-algorithm
// The pseudo-algorithm below determines the used values for column-count (N) and column-width (W). There is
// one other variable in the pseudo-algorithm: U is the used width of the multi-column container.
Optional<int> BlockFormattingContext::determine_used_value_for_column_count(CSSPixels const& U) const
{
    auto const& computed_values = root().computed_values();
    // (01)  if ((column-width = auto) and (column-count = auto)) then
    if (computed_values.column_width().is_auto() && computed_values.column_count().is_auto()) {
        // (02)      exit; /* not a multicol container */
        return {};
    }

    // (03)  if column-width = auto then
    if (computed_values.column_width().is_auto()) {
        // (04)      N := column-count
        return computed_values.column_count().value();
    }

    auto column_gap = get_column_gap_used_value_for_multicol(U);
    auto column_width = get_column_width_used_value_for_multicol(U);

    // (05)  else if column-count = auto then
    if (computed_values.column_count().is_auto()) {
        // (06)      N := max(1,
        // (07)        floor((U + column-gap)/(column-width + column-gap)))
        return max(1, ((U + column_gap) / (column_width + column_gap)).to_int());
    }

    // (08)  else
    // (09)      N := min(column-count, max(1,
    // (10)        floor((U + column-gap)/(column-width + column-gap))))
    return min(computed_values.column_count().value(), max(1, ((U + column_gap) / (column_width + column_gap)).to_int()));
}
CSSPixels BlockFormattingContext::determine_used_value_for_column_width(CSSPixels const& U, int N) const
{
    auto column_gap = get_column_gap_used_value_for_multicol(U);
    // (11)  W := max(0, (U + column-gap)/N - column-gap)
    return max(CSSPixels(0), (U + column_gap) / N - column_gap);
}

// https://drafts.csswg.org/css-multicol-2/#cw
CSSPixels BlockFormattingContext::get_column_width_used_value_for_multicol(CSSPixels const& U) const
{
    // Used values will be clamped to a minimum of '1px'.
    return max(root().computed_values().column_width().to_px(root(), U), 1);
}

// https://www.w3.org/TR/css-align-3/#column-row-gap
CSSPixels BlockFormattingContext::get_column_gap_used_value_for_multicol(CSSPixels const& U) const
{
    // The 'normal' represents a used value of '1em' on multi-column containers
    return root().computed_values().column_gap().visit(
        [&](CSS::NormalGap) { return CSS::Length(1, CSS::LengthUnit::Em).to_px(root()); },
        [&](auto const& gap) { return gap.to_px(root(), U); });
}

}