ladybird/Userland/Libraries/LibWeb/DOM/StyleElementUtils.cpp

/*
 * Copyright (c) 2023, Preston Taylor <PrestonLeeTaylor@proton.me>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/CSS/Parser/Parser.h>
#include <LibWeb/CSS/StyleComputer.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/ShadowRoot.h>
#include <LibWeb/DOM/StyleElementUtils.h>
#include <LibWeb/Infra/Strings.h>

namespace Web::DOM {

static CSS::StyleSheetList& relevant_style_sheet_list_for_node(DOM::Node& node)
{
    auto& root_node = node.root();
    if (is<DOM::ShadowRoot>(root_node))
        return static_cast<DOM::ShadowRoot&>(root_node).style_sheets();

    return node.document().style_sheets();
}

// The user agent must run the "update a style block" algorithm whenever one of the following conditions occur:
// FIXME: The element is popped off the stack of open elements of an HTML parser or XML parser.
//
// NOTE: This is basically done by children_changed() today:
// The element's children changed steps run.
//
// NOTE: This is basically done by inserted() and removed_from() today:
// The element is not on the stack of open elements of an HTML parser or XML parser, and it becomes connected or disconnected.
//
// https://html.spec.whatwg.org/multipage/semantics.html#update-a-style-block
void StyleElementUtils::update_a_style_block(DOM::Element& style_element, JS::GCPtr<DOM::Node> old_parent_if_removed_from)
{
    // OPTIMIZATION: Skip parsing CSS if we're in the middle of parsing a HTML fragment.
    //               The style block will be parsed upon insertion into a proper document.
    if (style_element.document().is_temporary_document_for_fragment_parsing())
        return;

    // 1. Let element be the style element.
    // 2. If element has an associated CSS style sheet, remove the CSS style sheet in question.

    if (m_associated_css_style_sheet) {
        // NOTE: If we're here in response to a node being removed from the tree, we need to remove the stylesheet from the style scope
        //       of the old parent, not the style scope of the node itself, since it's too late to find it that way!
        if (old_parent_if_removed_from) {
            relevant_style_sheet_list_for_node(*old_parent_if_removed_from).remove_a_css_style_sheet(*m_associated_css_style_sheet);
        } else {
            style_element.document_or_shadow_root_style_sheets().remove_a_css_style_sheet(*m_associated_css_style_sheet);
        }

        // FIXME: This should probably be handled by StyleSheet::set_owner_node().
        m_associated_css_style_sheet = nullptr;
    }

    // 3. If element is not connected, then return.
    if (!style_element.is_connected())
        return;

    // 4. If element's type attribute is present and its value is neither the empty string nor an ASCII case-insensitive match for "text/css", then return.
    auto type_attribute = style_element.attribute(HTML::AttributeNames::type);
    if (type_attribute.has_value() && !type_attribute->is_empty() && !Infra::is_ascii_case_insensitive_match(type_attribute->bytes_as_string_view(), "text/css"sv))
        return;

    // FIXME: 5. If the Should element's inline behavior be blocked by Content Security Policy? algorithm returns "Blocked" when executed upon the style element, "style", and the style element's child text content, then return. [CSP]

    // FIXME: This is a bit awkward, as the spec doesn't actually tell us when to parse the CSS text,
    //        so we just do it here and pass the parsed sheet to create_a_css_style_sheet().
    auto* sheet = parse_css_stylesheet(CSS::Parser::ParsingContext(style_element.document()), style_element.text_content().value_or(String {}));
    if (!sheet)
        return;

    // FIXME: This should probably be handled by StyleSheet::set_owner_node().
    m_associated_css_style_sheet = sheet;

    // 6. Create a CSS style sheet with the following properties...
    style_element.document_or_shadow_root_style_sheets().create_a_css_style_sheet(
        "text/css"_string,
        &style_element,
        style_element.attribute(HTML::AttributeNames::media).value_or({}),
        style_element.in_a_document_tree()
            ? style_element.attribute(HTML::AttributeNames::title).value_or({})
            : String {},
        false,
        true,
        {},
        nullptr,
        nullptr,
        *sheet);
}

}