ladybird/Libraries/LibWeb/Layout/Node.h

/*
 * Copyright (c) 2018-2025, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/DoublyLinkedList.h>
#include <AK/NonnullOwnPtr.h>
#include <AK/NonnullRefPtr.h>
#include <AK/RefCounted.h>
#include <AK/Vector.h>
#include <AK/WeakPtr.h>
#include <AK/Weakable.h>
#include <LibGC/Cell.h>
#include <LibGC/Weak.h>
#include <LibWeb/CSS/StyleValues/AbstractImageStyleValue.h>
#include <LibWeb/CSS/StyleValues/ImageStyleValue.h>
#include <LibWeb/Export.h>
#include <LibWeb/Forward.h>
#include <LibWeb/Painting/DisplayListRecordingContext.h>
#include <LibWeb/Painting/Paintable.h>
#include <LibWeb/RefCountedTreeNode.h>

namespace Web::Layout {

#define LAYOUT_NODE(class_, base_class)            \
public:                                            \
    using Base = base_class;                       \
    virtual StringView class_name() const override \
    {                                              \
        return #class_##sv;                        \
    }

class InlineNode;

enum class LayoutMode {
    // Normal layout. No min-content or max-content constraints applied.
    Normal,

    // Intrinsic size determination.
    // Boxes honor min-content and max-content constraints (set via LayoutState::UsedValues::{width,height}_constraint)
    // by considering their containing block to be 0-sized or infinitely large in the relevant axis.
    // https://drafts.csswg.org/css-sizing-3/#intrinsic-sizing
    IntrinsicSizing,
};

class WEB_API Node
    : public RefCounted<Node>
    , public Weakable<Node>
    , public RefCountedTreeNode<Node> {

public:
    using Base = RefCountedTreeNode<Node>;

    virtual ~Node();
    virtual StringView class_name() const { return "Node"sv; }

    bool is_anonymous() const;
    DOM::Node const* dom_node() const;
    DOM::Node* dom_node();

    DOM::Element const* pseudo_element_generator() const;
    DOM::Element* pseudo_element_generator();

    bool needs_layout_update() const { return m_needs_layout_update; }
    void set_needs_layout_update(DOM::SetNeedsLayoutReason);
    void reset_needs_layout_update() { m_needs_layout_update = false; }

    bool is_generated_for_pseudo_element() const { return m_generated_for.has_value(); }
    Optional<CSS::PseudoElement> generated_for_pseudo_element() const { return m_generated_for; }
    bool is_generated_for_before_pseudo_element() const { return m_generated_for == CSS::PseudoElement::Before; }
    bool is_generated_for_after_pseudo_element() const { return m_generated_for == CSS::PseudoElement::After; }
    bool is_generated_for_backdrop_pseudo_element() const { return m_generated_for == CSS::PseudoElement::Backdrop; }
    void set_generated_for(CSS::PseudoElement type, DOM::Element&);

    using PaintableList = DoublyLinkedList<NonnullRefPtr<Painting::Paintable>>;

    RefPtr<Painting::Paintable> first_paintable()
    {
        if (m_paintable.is_empty())
            return nullptr;
        return m_paintable.first();
    }
    RefPtr<Painting::Paintable const> first_paintable() const
    {
        if (m_paintable.is_empty())
            return nullptr;
        return m_paintable.first();
    }
    PaintableList& paintables() { return m_paintable; }
    PaintableList const& paintables() const { return m_paintable; }
    void add_paintable(RefPtr<Painting::Paintable>);
    void clear_paintables();
    void prepare_for_detach_from_layout_tree();
    void prepare_subtree_for_detach_from_layout_tree();

    virtual RefPtr<Painting::Paintable> create_paintable() const;

    DOM::Document& document();
    DOM::Document const& document() const;

    GC::Ptr<HTML::Navigable> navigable() const;

    Viewport const& root() const;
    Viewport& root();

    bool is_root_element() const;

    String debug_description() const;

    bool has_style() const { return m_has_style; }
    bool has_style_or_parent_with_style() const;

    virtual bool can_have_children() const { return true; }

    CSS::Display display() const;
    CSS::Display display_before_box_type_transformation() const;

    bool is_inline() const;
    bool is_inline_block() const;
    bool is_inline_table() const;

    bool is_atomic_inline() const;

    bool is_out_of_flow(FormattingContext const&) const;

    // These are used to optimize hot is<T> variants for some classes where dynamic_cast is too slow.
    virtual bool is_box() const { return false; }
    virtual bool is_block_container() const { return false; }
    virtual bool is_inline_node() const { return false; }
    virtual bool is_break_node() const { return false; }
    virtual bool is_text_node() const { return false; }
    virtual bool is_text_slice_node() const { return false; }
    virtual bool is_viewport() const { return false; }
    virtual bool is_svg_box() const { return false; }
    virtual bool is_svg_geometry_box() const { return false; }
    virtual bool is_svg_clip_box() const { return false; }
    virtual bool is_svg_mask_box() const { return false; }
    virtual bool is_svg_pattern_box() const { return false; }
    virtual bool is_svg_svg_box() const { return false; }
    virtual bool is_svg_graphics_box() const { return false; }
    virtual bool is_svg_foreign_object_box() const { return false; }
    virtual bool is_label() const { return false; }
    virtual bool is_replaced_box() const { return false; }
    virtual bool is_textarea_box() const { return false; }
    virtual bool is_list_item_box() const { return false; }
    virtual bool is_list_item_marker_box() const { return false; }
    virtual bool is_fieldset_box() const { return false; }
    virtual bool is_legend_box() const { return false; }
    virtual bool is_table_wrapper() const { return false; }
    virtual bool is_node_with_style() const { return false; }
    virtual bool is_node_with_style_and_box_model_metrics() const { return false; }

    bool is_replaced_box_with_children() const { return is_replaced_box() && can_have_children(); }

    template<typename T>
    bool fast_is() const = delete;

    bool is_floating() const;
    bool is_positioned() const;
    bool is_absolutely_positioned() const;
    bool is_fixed_position() const;
    bool is_sticky_position() const;

    bool is_flex_item() const { return m_is_flex_item; }
    void set_flex_item(bool b) { m_is_flex_item = b; }

    bool is_grid_item() const { return m_is_grid_item; }
    void set_grid_item(bool b) { m_is_grid_item = b; }

    bool vertical_align_applies() const
    {
        // https://drafts.csswg.org/css-flexbox/#flex-containers
        // "vertical-align has no effect on a flex item"
        if (is_flex_item())
            return false;
        // https://drafts.csswg.org/css-grid-1/#grid-container
        // "vertical-align has no effect on a grid item"
        if (is_grid_item())
            return false;
        // FIXME: Per-spec, vertical-align only applies to inline-level boxes and table cells; this should be narrowed
        //        to that — rather than only excluding flex and grid items.
        return true;
    }

    [[nodiscard]] Box const* containing_block() const { return m_containing_block; }
    [[nodiscard]] Box* containing_block() { return m_containing_block; }

    // Returns the inline node that actually establishes the containing block for this absolutely
    // positioned element, if applicable. This is needed because m_containing_block can only hold
    // a Box*, but CSS allows inline elements (like a <span> with position:relative) to establish
    // containing blocks for their absolutely positioned descendants.
    // See the large FIXME comment in FormattingContext.cpp for full context.
    [[nodiscard]] InlineNode const* inline_containing_block_if_applicable() const { return m_inline_containing_block_if_applicable; }

    void recompute_containing_block(Badge<DOM::Document>);

    [[nodiscard]] Box const* static_position_containing_block() const;
    [[nodiscard]] Box* static_position_containing_block() { return const_cast<Box*>(const_cast<Node const*>(this)->static_position_containing_block()); }

    // Closest non-anonymous ancestor box, to be used when resolving percentage values.
    // Anonymous block boxes are ignored when resolving percentage values that would refer to it:
    // the closest non-anonymous ancestor box is used instead.
    // https://www.w3.org/TR/CSS22/visuren.html#anonymous-block-level
    Box const* non_anonymous_containing_block() const;

    bool establishes_stacking_context() const;

    bool computed_values_establish_absolute_positioning_containing_block() const;
    bool establishes_an_absolute_positioning_containing_block() const;
    bool establishes_a_fixed_positioning_containing_block() const;

    Gfx::Font const& first_available_font() const;
    Gfx::Font const& font(DisplayListRecordingContext&) const;
    Gfx::Font const& font(float scale_factor) const;

    CSS::ImmutableComputedValues const& computed_values() const;

    NodeWithStyle* parent();
    NodeWithStyle const* parent() const;

    void inserted_into(Node&) { }
    void removed_from(Node&) { }
    void children_changed() { }

    bool children_are_inline() const { return m_children_are_inline; }
    void set_children_are_inline(bool value) { m_children_are_inline = value; }

    u32 initial_quote_nesting_level() const { return m_initial_quote_nesting_level; }
    void set_initial_quote_nesting_level(u32 value) { m_initial_quote_nesting_level = value; }

    // An element is called out of flow if it is floated, absolutely positioned, or is the root element.
    // https://www.w3.org/TR/CSS22/visuren.html#positioning-scheme
    bool is_out_of_flow() const { return is_floating() || is_absolutely_positioned(); }

    // An element is called in-flow if it is not out-of-flow.
    // https://www.w3.org/TR/CSS22/visuren.html#positioning-scheme
    bool is_in_flow() const { return !is_out_of_flow(); }

    [[nodiscard]] bool has_css_transform() const
    {
        auto const& computed_values = this->computed_values();
        return !computed_values.transformations().is_empty()
            || computed_values.rotate()
            || computed_values.translate()
            || computed_values.scale();
    }

    // https://drafts.csswg.org/css-ui/#propdef-user-select
    CSS::UserSelect user_select_used_value() const;

    // https://drafts.csswg.org/css-contain-2/#containment-types
    bool has_size_containment() const;
    bool has_inline_size_containment() const;
    bool has_layout_containment() const;
    bool has_style_containment() const;
    bool has_paint_containment() const;

    [[nodiscard]] bool has_been_wrapped_in_table_wrapper() const { return m_has_been_wrapped_in_table_wrapper; }
    void set_has_been_wrapped_in_table_wrapper(bool value) { m_has_been_wrapped_in_table_wrapper = value; }

    enum class AttachToDOMNode {
        No,
        Yes,
    };

protected:
    Node(DOM::Document&, DOM::Node*, AttachToDOMNode = AttachToDOMNode::Yes);

private:
    friend class NodeWithStyle;

    GC::Weak<DOM::Node> m_dom_node;
    PaintableList m_paintable;

    Box* m_containing_block { nullptr };

    // For absolutely positioned elements, if there's an inline element (like a <span> with
    // position:relative) that should be the containing block but can't be stored in m_containing_block
    // (because it's not a Box), we store it here. This happens when a block element is inside an
    // inline element - the layout tree restructures so the block becomes a sibling of the inline,
    // but the CSS containing block relationship is based on the DOM structure.
    InlineNode const* m_inline_containing_block_if_applicable { nullptr };

    GC::Weak<DOM::Element> m_pseudo_element_generator;

    bool m_anonymous { false };
    bool m_has_style { false };
    bool m_children_are_inline { false };

    bool m_is_flex_item { false };
    bool m_is_grid_item { false };

    bool m_has_been_wrapped_in_table_wrapper { false };
    bool m_is_body { false };

    bool m_needs_layout_update { false };

    Optional<CSS::PseudoElement> m_generated_for;

    u32 m_initial_quote_nesting_level { 0 };
};

class WEB_API NodeWithStyle : public Node {
    LAYOUT_NODE(NodeWithStyle, Node);

public:
    virtual ~NodeWithStyle() override;

    class ImageObserver final : public CSS::ImageStyleValue::Client {
    public:
        ImageObserver(NodeWithStyle&, NonnullRefPtr<CSS::ImageStyleValue const> image);
        virtual ~ImageObserver() override;

        virtual void image_style_value_did_update(CSS::ImageStyleValue&) override;

    private:
        WeakPtr<NodeWithStyle> m_owner;
        NonnullRefPtr<CSS::ImageStyleValue const> m_image;
    };

    CSS::ImmutableComputedValues const& computed_values() const { return static_cast<CSS::ImmutableComputedValues const&>(*m_computed_values); }
    CSS::MutableComputedValues& mutable_computed_values() { return static_cast<CSS::MutableComputedValues&>(*m_computed_values); }

    void clear_image_observers();
    void apply_style(CSS::ComputedProperties const&);

    Gfx::Font const& first_available_font() const;
    Vector<CSS::BackgroundLayerData> const& background_layers() const { return computed_values().background_layers(); }
    CSS::AbstractImageStyleValue const* list_style_image() const { return m_list_style_image; }
    CSS::StyleScope const& style_scope() const;

    NonnullRefPtr<NodeWithStyle> create_anonymous_wrapper() const;

    void transfer_table_box_computed_values_to_wrapper_computed_values(CSS::ComputedValues& wrapper_computed_values);

    bool is_body() const { return m_is_body; }
    bool is_scroll_container() const;

    void set_computed_values(NonnullOwnPtr<CSS::ComputedValues>);

    u32 layout_index() const { return m_layout_index; }
    void set_layout_index(u32 index) { m_layout_index = index; }

protected:
    NodeWithStyle(DOM::Document&, DOM::Node*, CSS::ComputedProperties const&);
    NodeWithStyle(DOM::Document&, DOM::Node*, NonnullOwnPtr<CSS::ComputedValues>);

private:
    virtual bool is_node_with_style() const final { return true; }

    void reset_table_box_computed_values_used_by_wrapper_to_init_values();
    void propagate_non_inherit_values(NodeWithStyle& target_node) const;
    void propagate_style_to_anonymous_wrappers();

    void rebuild_image_observers();

    NonnullOwnPtr<CSS::ComputedValues> m_computed_values;
    RefPtr<CSS::AbstractImageStyleValue const> m_list_style_image;
    Vector<NonnullOwnPtr<ImageObserver>> m_image_observers;
    u32 m_layout_index { 0 };
};

template<>
inline bool Node::fast_is<NodeWithStyle>() const { return is_node_with_style(); }

class NodeWithStyleAndBoxModelMetrics : public NodeWithStyle {
    LAYOUT_NODE(NodeWithStyleAndBoxModelMetrics, NodeWithStyle);

public:
    NodeWithStyleAndBoxModelMetrics* continuation_of_node() const { return m_continuation_of_node.ptr(); }
    void set_continuation_of_node(Badge<TreeBuilder>, NodeWithStyleAndBoxModelMetrics* node) { m_continuation_of_node = node; }

    bool should_create_inline_continuation() const;

    void propagate_style_along_continuation(CSS::ComputedProperties const&) const;

protected:
    NodeWithStyleAndBoxModelMetrics(DOM::Document&, DOM::Node*, CSS::ComputedProperties const&);

    NodeWithStyleAndBoxModelMetrics(DOM::Document& document, DOM::Node* node, NonnullOwnPtr<CSS::ComputedValues> computed_values)
        : NodeWithStyle(document, node, move(computed_values))
    {
    }

private:
    virtual bool is_node_with_style_and_box_model_metrics() const final { return true; }

    WeakPtr<NodeWithStyleAndBoxModelMetrics> m_continuation_of_node;
};

template<>
inline bool Node::fast_is<NodeWithStyleAndBoxModelMetrics>() const { return is_node_with_style_and_box_model_metrics(); }

inline bool Node::has_style_or_parent_with_style() const
{
    return m_has_style || (parent() != nullptr && parent()->has_style_or_parent_with_style());
}

inline Gfx::Font const& Node::first_available_font() const
{
    VERIFY(has_style_or_parent_with_style());
    if (m_has_style)
        return static_cast<NodeWithStyle const*>(this)->first_available_font();
    return parent()->first_available_font();
}

inline Gfx::Font const& Node::font(DisplayListRecordingContext& context) const
{
    return font(context.device_pixels_per_css_pixel());
}

inline Gfx::Font const& Node::font(float scale_factor) const
{
    auto const& font = first_available_font();
    return font.with_size(font.point_size() * scale_factor);
}

inline CSS::ImmutableComputedValues const& Node::computed_values() const
{
    VERIFY(has_style_or_parent_with_style());

    if (m_has_style)
        return static_cast<NodeWithStyle const*>(this)->computed_values();
    return parent()->computed_values();
}

inline NodeWithStyle const* Node::parent() const
{
    return static_cast<NodeWithStyle const*>(Base::parent().ptr());
}

inline NodeWithStyle* Node::parent()
{
    return static_cast<NodeWithStyle*>(Base::parent().ptr());
}

inline Gfx::Font const& NodeWithStyle::first_available_font() const
{
    // https://drafts.csswg.org/css-fonts/#first-available-font
    // First font for which the character U+0020 (space) is not excluded by a unicode-range
    return computed_values().font_list().font_for_code_point(' ');
}

bool overflow_value_makes_box_a_scroll_container(CSS::Overflow overflow);

}