text: /*
   * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include <LibWeb/CSS/Length.h>
  #include <LibWeb/DOM/Node.h>
  #include <LibWeb/Layout/BlockBox.h>
  #include <LibWeb/Layout/BlockFormattingContext.h>
  #include <LibWeb/Layout/Box.h>
  #include <LibWeb/Layout/InitialContainingBlockBox.h>
  #include <LibWeb/Layout/InlineFormattingContext.h>
  #include <LibWeb/Layout/ListItemBox.h>
  #include <LibWeb/Layout/ReplacedBox.h>
  #include <LibWeb/Page/Frame.h>
  
  namespace Web::Layout {
  
  BlockFormattingContext::BlockFormattingContext(Box& context_box, FormattingContext* parent)
      : FormattingContext(context_box, parent)
  {
  }
  
  BlockFormattingContext::~BlockFormattingContext()
  {
  }
  
  bool BlockFormattingContext::is_initial() const
  {
      return is<InitialContainingBlockBox>(context_box());
  }
  
  void BlockFormattingContext::run(Box& box, LayoutMode layout_mode)
  {
      if (is_initial()) {
          layout_initial_containing_block(layout_mode);
          return;
      }
  
      // FIXME: BFC currently computes the width+height of the target box.
      //        This is necessary to be able to place absolutely positioned descendants.
      //        The same work is also done by the parent BFC for each of its blocks..
  
      if (layout_mode == LayoutMode::Default)
          compute_width(box);
  
      if (box.children_are_inline()) {
          layout_inline_children(box, layout_mode);
      } else {
          layout_block_level_children(box, layout_mode);
      }
  
      if (layout_mode == LayoutMode::Default) {
          compute_height(box);
  
          box.for_each_child_of_type<Box>([&](auto& child_box) {
              if (child_box.is_absolutely_positioned()) {
                  layout_absolutely_positioned_element(child_box);
              }
              return IterationDecision::Continue;
          });
      }
  }
  
  void BlockFormattingContext::compute_width(Box& box)
  {
      if (box.is_absolutely_positioned()) {
          compute_width_for_absolutely_positioned_element(box);
          return;
      }
  
      if (is<ReplacedBox>(box)) {
          // FIXME: This should not be done *by* ReplacedBox
          auto& replaced = downcast<ReplacedBox>(box);
          replaced.prepare_for_replaced_layout();
          compute_width_for_block_level_replaced_element_in_normal_flow(replaced);
          return;
      }
  
      if (box.is_floating()) {
          compute_width_for_floating_box(box);
          return;
      }
  
      auto& computed_values = box.computed_values();
      float width_of_containing_block = box.width_of_logical_containing_block();
  
      auto zero_value = CSS::Length::make_px(0);
  
      auto margin_left = CSS::Length::make_auto();
      auto margin_right = CSS::Length::make_auto();
      const auto padding_left = computed_values.padding().left.resolved_or_zero(box, width_of_containing_block);
      const auto padding_right = computed_values.padding().right.resolved_or_zero(box, width_of_containing_block);
  
      auto try_compute_width = [&](const auto& a_width) {
          CSS::Length width = a_width;
          margin_left = computed_values.margin().left.resolved_or_zero(box, width_of_containing_block);
          margin_right = computed_values.margin().right.resolved_or_zero(box, width_of_containing_block);
  
          float total_px = computed_values.border_left().width + computed_values.border_right().width;
          for (auto& value : { margin_left, padding_left, width, padding_right, margin_right }) {
              total_px += value.to_px(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 > width_of_containing_block) {
                  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 = width_of_containing_block - total_px;
  
              if (width.is_auto()) {
                  if (margin_left.is_auto())
                      margin_left = zero_value;
                  if (margin_right.is_auto())
                      margin_right = zero_value;
                  if (underflow_px >= 0) {
                      width = CSS::Length(underflow_px, CSS::Length::Type::Px);
                  } else {
                      width = zero_value;
                      margin_right = CSS::Length(margin_right.to_px(box) + underflow_px, CSS::Length::Type::Px);
                  }
              } else {
                  if (!margin_left.is_auto() && !margin_right.is_auto()) {
                      margin_right = CSS::Length(margin_right.to_px(box) + underflow_px, CSS::Length::Type::Px);
                  } else if (!margin_left.is_auto() && margin_right.is_auto()) {
                      margin_right = CSS::Length(underflow_px, CSS::Length::Type::Px);
                  } else if (margin_left.is_auto() && !margin_right.is_auto()) {
                      margin_left = CSS::Length(underflow_px, CSS::Length::Type::Px);
                  } else { // margin_left.is_auto() && margin_right.is_auto()
                      auto half_of_the_underflow = CSS::Length(underflow_px / 2, CSS::Length::Type::Px);
                      margin_left = half_of_the_underflow;
                      margin_right = half_of_the_underflow;
                  }
              }
          } else if (box.is_inline_block()) {
  
              // 10.3.9 'Inline-block', non-replaced elements in normal flow
  
              // A computed value of 'auto' for 'margin-left' or 'margin-right' becomes a used value of '0'.
              if (margin_left.is_auto())
                  margin_left = zero_value;
              if (margin_right.is_auto())
                  margin_right = zero_value;
  
              // If 'width' is 'auto', the used value is the shrink-to-fit width as for floating elements.
              if (width.is_auto()) {
  
                  // 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.
                  float available_width = width_of_containing_block
                      - margin_left.to_px(box) - computed_values.border_left().width - padding_left.to_px(box)
                      - padding_right.to_px(box) - computed_values.border_right().width - margin_right.to_px(box);
  
                  auto result = calculate_shrink_to_fit_widths(box);
  
                  // Then the shrink-to-fit width is: min(max(preferred minimum width, available width), preferred width).
                  width = CSS::Length(min(max(result.preferred_minimum_width, available_width), result.preferred_width), CSS::Length::Type::Px);
              }
          }
  
          return width;
      };
  
      auto specified_width = computed_values.width().resolved_or_auto(box, width_of_containing_block);
  
      // 1. The tentative used width is calculated (without 'min-width' and 'max-width')
      auto used_width = try_compute_width(specified_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'.
      auto specified_max_width = computed_values.max_width().resolved_or_auto(box, width_of_containing_block);
      if (!specified_max_width.is_auto()) {
          if (used_width.to_px(box) > specified_max_width.to_px(box)) {
              used_width = try_compute_width(specified_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'.
      auto specified_min_width = computed_values.min_width().resolved_or_auto(box, width_of_containing_block);
      if (!specified_min_width.is_auto()) {
          if (used_width.to_px(box) < specified_min_width.to_px(box)) {
              used_width = try_compute_width(specified_min_width);
          }
      }
  
      box.set_width(used_width.to_px(box));
      box.box_model().margin.left = margin_left.to_px(box);
      box.box_model().margin.right = margin_right.to_px(box);
      box.box_model().border.left = computed_values.border_left().width;
      box.box_model().border.right = computed_values.border_right().width;
      box.box_model().padding.left = padding_left.to_px(box);
      box.box_model().padding.right = padding_right.to_px(box);
  }
  
  void BlockFormattingContext::compute_width_for_floating_box(Box& box)
  {
      // 10.3.5 Floating, non-replaced elements
      auto& computed_values = box.computed_values();
      float width_of_containing_block = box.width_of_logical_containing_block();
      auto zero_value = CSS::Length::make_px(0);
  
      auto margin_left = CSS::Length::make_auto();
      auto margin_right = CSS::Length::make_auto();
      const auto padding_left = computed_values.padding().left.resolved_or_zero(box, width_of_containing_block);
      const auto padding_right = computed_values.padding().right.resolved_or_zero(box, width_of_containing_block);
  
      // If 'margin-left', or 'margin-right' are computed as 'auto', their used value is '0'.
      if (margin_left.is_auto())
          margin_left = zero_value;
      if (margin_right.is_auto())
          margin_right = zero_value;
  
      auto width = computed_values.width().resolved_or_auto(box, width_of_containing_block);
  
      // If 'width' is computed as 'auto', the used value is the "shrink-to-fit" width.
      if (width.is_auto()) {
  
          // 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.
          float available_width = width_of_containing_block
              - margin_left.to_px(box) - computed_values.border_left().width - padding_left.to_px(box)
              - padding_right.to_px(box) - computed_values.border_right().width - margin_right.to_px(box);
  
          auto result = calculate_shrink_to_fit_widths(box);
  
          // Then the shrink-to-fit width is: min(max(preferred minimum width, available width), preferred width).
          width = CSS::Length(min(max(result.preferred_minimum_width, available_width), result.preferred_width), CSS::Length::Type::Px);
      }
  
      float final_width = width.resolved_or_zero(box, width_of_containing_block).to_px(box);
      box.set_width(final_width);
  }
  
  void BlockFormattingContext::compute_width_for_block_level_replaced_element_in_normal_flow(ReplacedBox& box)
  {
      box.set_width(compute_width_for_replaced_element(box));
  }
  
  void BlockFormattingContext::compute_height(Box& box)
  {
      auto& computed_values = box.computed_values();
      auto& containing_block = *box.containing_block();
  
      // First, resolve the top/bottom parts of the surrounding box model.
      box.box_model().margin.top = computed_values.margin().top.resolved_or_zero(box, containing_block.width()).to_px(box);
      box.box_model().margin.bottom = computed_values.margin().bottom.resolved_or_zero(box, containing_block.width()).to_px(box);
      box.box_model().border.top = computed_values.border_top().width;
      box.box_model().border.bottom = computed_values.border_bottom().width;
      box.box_model().padding.top = computed_values.padding().top.resolved_or_zero(box, containing_block.width()).to_px(box);
      box.box_model().padding.bottom = computed_values.padding().bottom.resolved_or_zero(box, containing_block.width()).to_px(box);
  
      // Then work out what the height is, based on box type and CSS properties.
      float height = 0;
      if (is<ReplacedBox>(box)) {
          height = compute_height_for_replaced_element(downcast<ReplacedBox>(box));
      } else {
          if (box.computed_values().height().is_undefined_or_auto()) {
              height = compute_auto_height_for_block_level_element(box);
          } else {
              CSS::Length specified_height;
              if (computed_values.height().is_percentage() && !containing_block.computed_values().height().is_absolute()) {
                  specified_height = CSS::Length::make_auto();
              } else {
                  specified_height = computed_values.height().resolved_or_auto(box, containing_block.height());
              }
  
              auto specified_max_height = computed_values.max_height().resolved_or_auto(box, containing_block.height());
              if (!specified_height.is_auto()) {
                  float used_height = specified_height.to_px(box);
                  if (!specified_max_height.is_auto())
                      used_height = min(used_height, specified_max_height.to_px(box));
                  height = used_height;
              }
          }
      }
  
      box.set_height(height);
  }
  
  void BlockFormattingContext::compute_position(Box& box)
  {
      // 9.4.3 Relative positioning
      // Once a box has been laid out according to the normal flow or floated, it may be shifted relative to this position.
  
      auto& box_model = box.box_model();
      auto& computed_values = box.computed_values();
      float width_of_containing_block = box.width_of_logical_containing_block();
  
      auto specified_left = computed_values.offset().left.resolved_or_zero(box, width_of_containing_block);
      auto specified_right = computed_values.offset().right.resolved_or_zero(box, width_of_containing_block);
  
      if (specified_left.is_auto() && specified_right.is_auto()) {
          // If both 'left' and 'right' are 'auto' (their initial values), the used values are '0' (i.e., the boxes stay in their original position).
          box_model.offset.left = 0;
          box_model.offset.right = 0;
      } else if (specified_left.is_auto()) {
          // If 'left' is 'auto', its used value is minus the value of 'right' (i.e., the boxes move to the left by the value of 'right').
          box_model.offset.right = specified_right.to_px(box);
          box_model.offset.left = 0 - box_model.offset.right;
      } else if (specified_right.is_auto()) {
          // If 'right' is specified as 'auto', its used value is minus the value of 'left'.
          box_model.offset.left = specified_left.to_px(box);
          box_model.offset.right = 0 - box_model.offset.left;
      } else {
          // If neither 'left' nor 'right' is 'auto', the position is over-constrained, and one of them has to be ignored.
          // If the 'direction' property of the containing block is 'ltr', the value of 'left' wins and 'right' becomes -'left'.
          // If 'direction' of the containing block is 'rtl', 'right' wins and 'left' is ignored.
          // FIXME: Check direction (assuming 'ltr' for now).
          box_model.offset.left = specified_left.to_px(box);
          box_model.offset.right = 0 - box_model.offset.left;
      }
  }
  
  void BlockFormattingContext::layout_inline_children(Box& box, LayoutMode layout_mode)
  {
      InlineFormattingContext context(box, this);
      context.run(box, layout_mode);
  }
  
  void BlockFormattingContext::layout_block_level_children(Box& box, LayoutMode layout_mode)
  {
      float content_height = 0;
      float content_width = 0;
  
      box.for_each_child_of_type<Box>([&](auto& child_box) {
          if (child_box.is_absolutely_positioned())
              return IterationDecision::Continue;
  
          if (child_box.is_floating()) {
              layout_floating_child(child_box, box);
              return IterationDecision::Continue;
          }
  
          compute_width(child_box);
          layout_inside(child_box, layout_mode);
          compute_height(child_box);
  
          if (child_box.computed_values().position() == CSS::Position::Relative)
              compute_position(child_box);
  
          if (is<ReplacedBox>(child_box))
              place_block_level_replaced_element_in_normal_flow(child_box, box);
          else if (is<BlockBox>(child_box))
              place_block_level_non_replaced_element_in_normal_flow(child_box, box);
  
          // FIXME: This should be factored differently. It's uncool that we mutate the tree *during* layout!
          //        Instead, we should generate the marker box during the tree build.
          if (is<ListItemBox>(child_box))
              downcast<ListItemBox>(child_box).layout_marker();
  
          content_height = max(content_height, child_box.effective_offset().y() + child_box.height() + child_box.box_model().margin_box().bottom);
          content_width = max(content_width, downcast<Box>(child_box).width());
          return IterationDecision::Continue;
      });
  
      if (layout_mode != LayoutMode::Default) {
          if (box.computed_values().width().is_undefined() || box.computed_values().width().is_auto())
              box.set_width(content_width);
      }
  }
  
  void BlockFormattingContext::place_block_level_replaced_element_in_normal_flow(Box& child_box, Box& containing_block)
  {
      VERIFY(!containing_block.is_absolutely_positioned());
      auto& replaced_element_box_model = child_box.box_model();
  
      replaced_element_box_model.margin.top = child_box.computed_values().margin().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
      replaced_element_box_model.margin.bottom = child_box.computed_values().margin().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
      replaced_element_box_model.border.top = child_box.computed_values().border_top().width;
      replaced_element_box_model.border.bottom = child_box.computed_values().border_bottom().width;
      replaced_element_box_model.padding.top = child_box.computed_values().padding().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
      replaced_element_box_model.padding.bottom = child_box.computed_values().padding().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
  
      float x = replaced_element_box_model.margin.left
          + replaced_element_box_model.border.left
          + replaced_element_box_model.padding.left
          + replaced_element_box_model.offset.left;
  
      float y = replaced_element_box_model.margin_box().top + containing_block.box_model().offset.top;
  
      child_box.set_offset(x, y);
  }
  
  void BlockFormattingContext::place_block_level_non_replaced_element_in_normal_flow(Box& child_box, Box& containing_block)
  {
      auto& box_model = child_box.box_model();
      auto& computed_values = child_box.computed_values();
  
      box_model.margin.top = computed_values.margin().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
      box_model.margin.bottom = computed_values.margin().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
      box_model.border.top = computed_values.border_top().width;
      box_model.border.bottom = computed_values.border_bottom().width;
      box_model.padding.top = computed_values.padding().top.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
      box_model.padding.bottom = computed_values.padding().bottom.resolved_or_zero(containing_block, containing_block.width()).to_px(child_box);
  
      float x = box_model.margin.left
          + box_model.border.left
          + box_model.padding.left
          + box_model.offset.left;
  
      if (containing_block.computed_values().text_align() == CSS::TextAlign::LibwebCenter) {
          x = (containing_block.width() / 2) - child_box.width() / 2;
      }
  
      float y = box_model.margin_box().top
          + box_model.offset.top;
  
      // NOTE: Empty (0-height) preceding siblings have their margins collapsed with *their* preceding sibling, etc.
      float collapsed_bottom_margin_of_preceding_siblings = 0;
  
      auto* relevant_sibling = child_box.previous_sibling_of_type<Layout::BlockBox>();
      while (relevant_sibling != nullptr) {
          if (!relevant_sibling->is_absolutely_positioned() && !relevant_sibling->is_floating()) {
              collapsed_bottom_margin_of_preceding_siblings = max(collapsed_bottom_margin_of_preceding_siblings, relevant_sibling->box_model().margin.bottom);
              if (relevant_sibling->border_box_height() > 0)
                  break;
          }
          relevant_sibling = relevant_sibling->previous_sibling();
      }
  
      if (relevant_sibling) {
          y += relevant_sibling->effective_offset().y()
              + relevant_sibling->height()
              + relevant_sibling->box_model().border_box().bottom;
  
          // Collapse top margin with bottom margin of preceding siblings if needed
          float my_margin_top = box_model.margin.top;
  
          if (my_margin_top < 0 || collapsed_bottom_margin_of_preceding_siblings < 0) {
              // Negative margins present.
              float largest_negative_margin = -min(my_margin_top, collapsed_bottom_margin_of_preceding_siblings);
              float largest_positive_margin = (my_margin_top < 0 && collapsed_bottom_margin_of_preceding_siblings < 0) ? 0 : max(my_margin_top, collapsed_bottom_margin_of_preceding_siblings);
              float final_margin = largest_positive_margin - largest_negative_margin;
              y += final_margin - my_margin_top;
          } else if (collapsed_bottom_margin_of_preceding_siblings > my_margin_top) {
              // Sibling's margin is larger than mine, adjust so we use sibling's.
              y += collapsed_bottom_margin_of_preceding_siblings - my_margin_top;
          }
      }
  
      if (child_box.computed_values().clear() == CSS::Clear::Left || child_box.computed_values().clear() == CSS::Clear::Both) {
          if (!m_left_floating_boxes.is_empty()) {
              float clearance_y = 0;
              for (auto* floating_box : m_left_floating_boxes) {
                  clearance_y = max(clearance_y, floating_box->effective_offset().y() + floating_box->box_model().margin_box().bottom);
              }
              y = max(y, clearance_y);
              m_left_floating_boxes.clear();
          }
      }
  
      if (child_box.computed_values().clear() == CSS::Clear::Right || child_box.computed_values().clear() == CSS::Clear::Both) {
          if (!m_right_floating_boxes.is_empty()) {
              float clearance_y = 0;
              for (auto* floating_box : m_right_floating_boxes) {
                  clearance_y = max(clearance_y, floating_box->effective_offset().y() + floating_box->box_model().margin_box().bottom);
              }
              y = max(y, clearance_y);
              m_right_floating_boxes.clear();
          }
      }
  
      child_box.set_offset(x, y);
  }
  
  void BlockFormattingContext::layout_initial_containing_block(LayoutMode layout_mode)
  {
      auto viewport_rect = context_box().frame().viewport_rect();
  
      auto& icb = downcast<Layout::InitialContainingBlockBox>(context_box());
      icb.build_stacking_context_tree();
  
      icb.set_width(viewport_rect.width());
  
      layout_block_level_children(context_box(), layout_mode);
  
      VERIFY(!icb.children_are_inline());
  
      // FIXME: The ICB should have the height of the viewport.
      //        Instead of auto-sizing the ICB, we should spill into overflow.
      float lowest_bottom = 0;
      icb.for_each_child_of_type<Box>([&](auto& child) {
          lowest_bottom = max(lowest_bottom, child.absolute_rect().bottom());
      });
  
      // FIXME: This is a hack and should be managed by an overflow mechanism.
      icb.set_height(max(static_cast<float>(viewport_rect.height()), lowest_bottom));
  }
  
  static Gfx::FloatRect rect_in_coordinate_space(const Box& box, const Box& context_box)
  {
      Gfx::FloatRect rect { box.effective_offset(), box.size() };
      for (auto* ancestor = box.parent(); ancestor; ancestor = ancestor->parent()) {
          if (is<Box>(*ancestor)) {
              auto offset = downcast<Box>(*ancestor).effective_offset();
              rect.move_by(offset);
          }
          if (ancestor == &context_box)
              break;
      }
      return rect;
  }
  
  void BlockFormattingContext::layout_floating_child(Box& box, Box& containing_block)
  {
      VERIFY(box.is_floating());
  
      compute_width(box);
      layout_inside(box, LayoutMode::Default);
      compute_height(box);
  
      // First we place the box normally (to get the right y coordinate.)
      place_block_level_non_replaced_element_in_normal_flow(box, containing_block);
  
      // Then we float it to the left or right.
      float x = box.effective_offset().x();
  
      auto box_in_context_rect = rect_in_coordinate_space(box, context_box());
      float y_in_context_box = box_in_context_rect.y();
  
      // Next, float to the left and/or right
      if (box.computed_values().float_() == CSS::Float::Left) {
          if (!m_left_floating_boxes.is_empty()) {
              auto& previous_floating_box = *m_left_floating_boxes.last();
              auto previous_rect = rect_in_coordinate_space(previous_floating_box, context_box());
              if (previous_rect.contains_vertically(y_in_context_box)) {
                  // This box touches another already floating box. Stack to the right.
                  x = previous_floating_box.effective_offset().x() + previous_floating_box.width();
              } else {
                  // This box does not touch another floating box, go all the way to the left.
                  x = 0;
                  // Also, forget all previous left-floating boxes while we're here since they're no longer relevant.
                  m_left_floating_boxes.clear();
              }
          } else {
              // This is the first left-floating box. Go all the way to the left.
              x = 0;
          }
          m_left_floating_boxes.append(&box);
      } else if (box.computed_values().float_() == CSS::Float::Right) {
          if (!m_right_floating_boxes.is_empty()) {
              auto& previous_floating_box = *m_right_floating_boxes.last();
              auto previous_rect = rect_in_coordinate_space(previous_floating_box, context_box());
              if (previous_rect.contains_vertically(y_in_context_box)) {
                  // This box touches another already floating box. Stack to the left.
                  x = previous_floating_box.effective_offset().x() - box.width();
              } else {
                  // This box does not touch another floating box, go all the way to the right.
                  x = containing_block.width() - box.width();
                  // Also, forget all previous right-floating boxes while we're here since they're no longer relevant.
                  m_right_floating_boxes.clear();
              }
          } else {
              // This is the first right-floating box. Go all the way to the right.
              x = containing_block.width() - box.width();
          }
          m_right_floating_boxes.append(&box);
      }
  
      box.set_offset(x, box.effective_offset().y());
  }
  
  }
  