serenity/Userland/Libraries/LibWeb/Layout/FormattingState.h

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

#pragma once

#include <AK/HashMap.h>
#include <LibGfx/Point.h>
#include <LibWeb/Layout/Box.h>
#include <LibWeb/Layout/LineBox.h>
#include <LibWeb/Painting/PaintableBox.h>

namespace Web::Layout {

enum class SizeConstraint {
    None,
    MinContent,
    MaxContent,
};

struct FormattingState {
    FormattingState()
        : m_root(*this)
    {
    }

    explicit FormattingState(FormattingState const* parent)
        : m_parent(parent)
        , m_root(find_root())
    {
    }

    FormattingState const& find_root() const
    {
        FormattingState const* root = this;
        for (auto* state = m_parent; state; state = state->m_parent)
            root = state;
        return *root;
    }

    struct NodeState {
        float content_width { 0 };
        float content_height { 0 };
        Gfx::FloatPoint offset;

        SizeConstraint width_constraint { SizeConstraint::None };
        SizeConstraint height_constraint { SizeConstraint::None };

        float margin_left { 0 };
        float margin_right { 0 };
        float margin_top { 0 };
        float margin_bottom { 0 };

        float border_left { 0 };
        float border_right { 0 };
        float border_top { 0 };
        float border_bottom { 0 };

        float padding_left { 0 };
        float padding_right { 0 };
        float padding_top { 0 };
        float padding_bottom { 0 };

        float inset_left { 0 };
        float inset_right { 0 };
        float inset_top { 0 };
        float inset_bottom { 0 };

        Vector<LineBox> line_boxes;

        float margin_box_left() const { return margin_left + border_left + padding_left; }
        float margin_box_right() const { return margin_right + border_right + padding_right; }
        float margin_box_top() const { return margin_top + border_top + padding_top; }
        float margin_box_bottom() const { return margin_bottom + border_bottom + padding_bottom; }

        float margin_box_width() const { return margin_box_left() + content_width + margin_box_right(); }
        float margin_box_height() const { return margin_box_top() + content_height + margin_box_bottom(); }

        float border_box_left() const { return border_left + padding_left; }
        float border_box_right() const { return border_right + padding_right; }
        float border_box_top() const { return border_top + padding_top; }
        float border_box_bottom() const { return border_bottom + padding_bottom; }

        float border_box_width() const { return border_box_left() + content_width + border_box_right(); }
        float border_box_height() const { return border_box_top() + content_height + border_box_bottom(); }

        Optional<Painting::PaintableBox::OverflowData> overflow_data;

        Painting::PaintableBox::OverflowData& ensure_overflow_data()
        {
            if (!overflow_data.has_value())
                overflow_data = Painting::PaintableBox::OverflowData {};
            return *overflow_data;
        }

        Optional<LineBoxFragmentCoordinate> containing_line_box_fragment;
    };

    void commit();

    // NOTE: get_mutable() will CoW the NodeState if it's inherited from an ancestor state;
    NodeState& get_mutable(NodeWithStyleAndBoxModelMetrics const&);

    // NOTE: get() will not CoW the NodeState.
    NodeState const& get(NodeWithStyleAndBoxModelMetrics const&) const;

    HashMap<NodeWithStyleAndBoxModelMetrics const*, NonnullOwnPtr<NodeState>> nodes;

    // We cache intrinsic sizes once determined, as they will not change over the course of a full layout.
    // This avoids computing them several times while performing flex layout.
    struct IntrinsicSizes {
        Optional<float> min_content_width;
        Optional<float> max_content_width;
        Optional<float> min_content_height;
        Optional<float> max_content_height;
    };

    HashMap<NodeWithStyleAndBoxModelMetrics const*, NonnullOwnPtr<IntrinsicSizes>> mutable intrinsic_sizes;

    HashMap<Box const*, float> mutable flex_item_size_cache;

    FormattingState const* m_parent { nullptr };
    FormattingState const& m_root;

    struct LookupCache {
        NodeWithStyleAndBoxModelMetrics const* box { nullptr };
        NodeState* state { nullptr };
        bool is_mutable { false };
    };
    LookupCache m_lookup_cache;
};

Gfx::FloatRect absolute_content_rect(Box const&, FormattingState const&);
Gfx::FloatRect margin_box_rect(Box const&, FormattingState const&);
Gfx::FloatRect margin_box_rect_in_ancestor_coordinate_space(Box const& box, Box const& ancestor_box, FormattingState const&);

}