ladybird/Userland/Libraries/LibWeb/Layout/FormattingState.cpp

/*
 * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/Layout/BlockContainer.h>
#include <LibWeb/Layout/FormattingState.h>

namespace Web::Layout {

FormattingState::NodeState& FormattingState::get_mutable(NodeWithStyleAndBoxModelMetrics const& box)
{
    auto state = nodes.ensure(&box, [] { return adopt_ref(*new NodeState); });
    // CoW if ref_count > 2 (1 for the entry in `this->nodes`, 1 for the `state` local in this function)
    if (state->ref_count > 2) {
        state = adopt_ref(*new NodeState { *state });
        state->ref_count = 1;
        nodes.set(&box, state);
    }
    return state;
}

FormattingState::NodeState const& FormattingState::get(NodeWithStyleAndBoxModelMetrics const& box) const
{
    return *const_cast<FormattingState&>(*this).nodes.ensure(&box, [] { return adopt_ref(*new NodeState); });
}

void FormattingState::commit()
{
    for (auto& it : nodes) {
        auto& node = const_cast<Layout::NodeWithStyleAndBoxModelMetrics&>(*it.key);
        auto& node_state = *it.value;

        // Transfer box model metrics.
        node.box_model().offset = { node_state.offset_top, node_state.offset_right, node_state.offset_bottom, node_state.offset_left };
        node.box_model().padding = { node_state.padding_top, node_state.padding_right, node_state.padding_bottom, node_state.padding_left };
        node.box_model().border = { node_state.border_top, node_state.border_right, node_state.border_bottom, node_state.border_left };
        node.box_model().margin = { node_state.margin_top, node_state.margin_right, node_state.margin_bottom, node_state.margin_left };

        // For boxes, transfer all the state needed for painting.
        if (is<Layout::Box>(node)) {
            auto& box = static_cast<Layout::Box&>(node);
            box.set_paint_box([](Layout::Box const& layout_box) -> OwnPtr<Painting::Box> {
                if (is<Layout::BlockContainer>(layout_box))
                    return Painting::BoxWithLines::create(static_cast<Layout::BlockContainer const&>(layout_box));
                return Painting::Box::create(static_cast<Layout::Box const&>(layout_box));
            }(box));
            box.m_paint_box->set_offset(node_state.offset);
            box.m_paint_box->set_content_size(node_state.content_width, node_state.content_height);
            box.m_paint_box->set_overflow_data(move(node_state.overflow_data));
            box.m_paint_box->set_containing_line_box_fragment(node_state.containing_line_box_fragment);

            if (is<Layout::BlockContainer>(box))
                static_cast<Painting::BoxWithLines&>(*box.m_paint_box).set_line_boxes(move(node_state.line_boxes));
        }
    }
}

Gfx::FloatRect margin_box_rect(Box const& box, FormattingState const& state)
{
    auto const& box_state = state.get(box);
    auto rect = Gfx::FloatRect { box_state.offset, { box_state.content_width, box_state.content_height } };
    rect.set_x(rect.x() - box_state.margin_box_left());
    rect.set_width(rect.width() + box_state.margin_box_left() + box_state.margin_box_right());
    rect.set_y(rect.y() - box_state.margin_box_top());
    rect.set_height(rect.height() + box_state.margin_box_top() + box_state.margin_box_bottom());
    return rect;
}

Gfx::FloatRect margin_box_rect_in_ancestor_coordinate_space(Box const& box, Box const& ancestor_box, FormattingState const& state)
{
    auto rect = margin_box_rect(box, state);
    for (auto const* current = box.parent(); current; current = current->parent()) {
        if (current == &ancestor_box)
            break;
        if (is<Box>(*current)) {
            auto const& current_state = state.get(static_cast<Box const&>(*current));
            rect.translate_by(current_state.offset);
        }
    }
    return rect;
}

Gfx::FloatRect absolute_content_rect(Box const& box, FormattingState const& state)
{
    auto const& box_state = state.get(box);
    Gfx::FloatRect rect { box_state.offset, { box_state.content_width, box_state.content_height } };
    for (auto* block = box.containing_block(); block; block = block->containing_block())
        rect.translate_by(state.get(*block).offset);
    return rect;
}

}