ladybird/Userland/Libraries/LibWeb/CSS/StyleSheetList.cpp

/*
 * Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/Bindings/StyleSheetListPrototype.h>
#include <LibWeb/CSS/StyleComputer.h>
#include <LibWeb/CSS/StyleSheetList.h>
#include <LibWeb/DOM/Document.h>

namespace Web::CSS {

JS_DEFINE_ALLOCATOR(StyleSheetList);

// https://www.w3.org/TR/cssom/#remove-a-css-style-sheet
void StyleSheetList::remove_a_css_style_sheet(CSS::CSSStyleSheet& sheet)
{
    // 1. Remove the CSS style sheet from the list of document or shadow root CSS style sheets.
    remove_sheet(sheet);

    // 2. Set the CSS style sheet’s parent CSS style sheet, owner node and owner CSS rule to null.
    sheet.set_parent_css_style_sheet(nullptr);
    sheet.set_owner_node(nullptr);
    sheet.set_owner_css_rule(nullptr);
}

// https://www.w3.org/TR/cssom/#add-a-css-style-sheet
void StyleSheetList::add_a_css_style_sheet(CSS::CSSStyleSheet& sheet)
{
    // 1. Add the CSS style sheet to the list of document or shadow root CSS style sheets at the appropriate location. The remainder of these steps deal with the disabled flag.
    add_sheet(sheet);

    // 2. If the disabled flag is set, then return.
    if (sheet.disabled())
        return;

    VERIFY(sheet.title().has_value());

    // 3. If the title is not the empty string, the alternate flag is unset, and preferred CSS style sheet set name is the empty string change the preferred CSS style sheet set name to the title.
    if (!sheet.title()->is_empty() && !sheet.is_alternate() && m_preferred_css_style_sheet_set_name.is_empty()) {
        m_preferred_css_style_sheet_set_name = sheet.title().value();
    }

    // 4. If any of the following is true, then unset the disabled flag and return:
    //    - The title is the empty string.
    //    - The last CSS style sheet set name is null and the title is a case-sensitive match for the preferred CSS style sheet set name.
    //    - The title is a case-sensitive match for the last CSS style sheet set name.
    // NOTE: We don't enable alternate sheets with an empty title.  This isn't directly mentioned in the algorithm steps, but the
    // HTML specification says that the title element must be specified with a non-empty value for alternative style sheets.
    // See: https://html.spec.whatwg.org/multipage/links.html#the-link-is-an-alternative-stylesheet
    if ((sheet.title()->is_empty() && !sheet.is_alternate())
        || (!m_last_css_style_sheet_set_name.has_value() && sheet.title().value().equals_ignoring_case(m_preferred_css_style_sheet_set_name))
        || (m_last_css_style_sheet_set_name.has_value() && sheet.title().value().equals_ignoring_case(m_last_css_style_sheet_set_name.value()))) {
        sheet.set_disabled(false);
        return;
    }

    // 5. Set the disabled flag.
    sheet.set_disabled(true);
}

// https://www.w3.org/TR/cssom/#create-a-css-style-sheet
void StyleSheetList::create_a_css_style_sheet(String type, DOM::Element* owner_node, String media, String title, bool alternate, bool origin_clean, Optional<String> location, CSS::CSSStyleSheet* parent_style_sheet, CSS::CSSRule* owner_rule, CSS::CSSStyleSheet& sheet)
{
    // 1. Create a new CSS style sheet object and set its properties as specified.
    // FIXME: We receive `sheet` from the caller already. This is weird.

    sheet.set_parent_css_style_sheet(parent_style_sheet);
    sheet.set_owner_css_rule(owner_rule);
    sheet.set_owner_node(owner_node);
    sheet.set_type(move(type));
    sheet.set_media(move(media));
    sheet.set_title(move(title));
    sheet.set_alternate(alternate);
    sheet.set_origin_clean(origin_clean);
    sheet.set_location(move(location));

    // 2. Then run the add a CSS style sheet steps for the newly created CSS style sheet.
    add_a_css_style_sheet(sheet);
}

void StyleSheetList::add_sheet(CSSStyleSheet& sheet)
{
    sheet.set_style_sheet_list({}, this);

    if (m_sheets.is_empty()) {
        // This is the first sheet, append it to the list.
        m_sheets.append(sheet);
    } else {
        // We have sheets from before. Insert the new sheet in the correct position (DOM tree order).
        bool did_insert = false;
        for (ssize_t i = m_sheets.size() - 1; i >= 0; --i) {
            auto& existing_sheet = *m_sheets[i];
            auto position = existing_sheet.owner_node()->compare_document_position(sheet.owner_node());
            if (position & DOM::Node::DocumentPosition::DOCUMENT_POSITION_FOLLOWING) {
                m_sheets.insert(i + 1, sheet);
                did_insert = true;
                break;
            }
        }
        if (!did_insert)
            m_sheets.prepend(sheet);
    }

    if (sheet.rules().length() == 0) {
        // NOTE: If the added sheet has no rules, we don't have to invalidate anything.
        return;
    }

    m_document->style_computer().invalidate_rule_cache();
    m_document->style_computer().load_fonts_from_sheet(sheet);
    m_document->invalidate_style();
}

void StyleSheetList::remove_sheet(CSSStyleSheet& sheet)
{
    sheet.set_style_sheet_list({}, nullptr);
    m_sheets.remove_first_matching([&](auto& entry) { return entry.ptr() == &sheet; });

    if (sheet.rules().length() == 0) {
        // NOTE: If the removed sheet had no rules, we don't have to invalidate anything.
        return;
    }

    m_document->style_computer().invalidate_rule_cache();
    m_document->invalidate_style();
}

JS::NonnullGCPtr<StyleSheetList> StyleSheetList::create(DOM::Document& document)
{
    auto& realm = document.realm();
    return realm.heap().allocate<StyleSheetList>(realm, document);
}

StyleSheetList::StyleSheetList(DOM::Document& document)
    : Bindings::PlatformObject(document.realm())
    , m_document(document)
{
    m_legacy_platform_object_flags = LegacyPlatformObjectFlags { .supports_indexed_properties = true };
}

void StyleSheetList::initialize(JS::Realm& realm)
{
    Base::initialize(realm);
    WEB_SET_PROTOTYPE_FOR_INTERFACE(StyleSheetList);
}

void StyleSheetList::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_document);
    visitor.visit(m_sheets);
}

// https://www.w3.org/TR/cssom/#ref-for-dfn-supported-property-indices%E2%91%A1
bool StyleSheetList::is_supported_property_index(u32 index) const
{
    // The object’s supported property indices are the numbers in the range zero to one less than the number of CSS style sheets represented by the collection.
    // If there are no such CSS style sheets, then there are no supported property indices.
    if (m_sheets.is_empty())
        return false;

    return index < m_sheets.size();
}

WebIDL::ExceptionOr<JS::Value> StyleSheetList::item_value(size_t index) const
{
    if (index >= m_sheets.size())
        return JS::js_undefined();

    return m_sheets[index].ptr();
}

}