third_party/WebKit/Source/core/dom/StyleElement.cpp

/*
 * Copyright (C) 2006, 2007 Rob Buis
 * Copyright (C) 2008 Apple, Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include "core/dom/StyleElement.h"

#include "bindings/core/v8/ScriptController.h"
#include "core/css/MediaList.h"
#include "core/css/MediaQueryEvaluator.h"
#include "core/css/StyleSheetContents.h"
#include "core/dom/Document.h"
#include "core/dom/Element.h"
#include "core/dom/ScriptableDocumentParser.h"
#include "core/dom/StyleEngine.h"
#include "core/dom/shadow/ShadowRoot.h"
#include "core/frame/LocalFrame.h"
#include "core/frame/csp/ContentSecurityPolicy.h"
#include "core/html/HTMLStyleElement.h"
#include "core/svg/SVGStyleElement.h"
#include "platform/tracing/TraceEvent.h"
#include "wtf/text/StringBuilder.h"

namespace blink {

static bool isCSS(const Element& element, const AtomicString& type) {
  return type.isEmpty() ||
         (element.isHTMLElement() ? equalIgnoringCase(type, "text/css")
                                  : (type == "text/css"));
}

StyleElement::StyleElement(Document* document, bool createdByParser)
    : m_createdByParser(createdByParser),
      m_loading(false),
      m_registeredAsCandidate(false),
      m_startPosition(TextPosition::belowRangePosition()) {
  if (createdByParser && document && document->scriptableDocumentParser() &&
      !document->isInDocumentWrite())
    m_startPosition = document->scriptableDocumentParser()->textPosition();
}

StyleElement::~StyleElement() {}

StyleElement::ProcessingResult StyleElement::processStyleSheet(
    Document& document,
    Element& element) {
  TRACE_EVENT0("blink", "StyleElement::processStyleSheet");
  DCHECK(element.isConnected());

  m_registeredAsCandidate = true;
  document.styleEngine().addStyleSheetCandidateNode(element);
  if (m_createdByParser)
    return ProcessingSuccessful;

  return process(element);
}

void StyleElement::removedFrom(Element& element,
                               ContainerNode* insertionPoint) {
  if (!insertionPoint->isConnected())
    return;

  Document& document = element.document();
  if (m_registeredAsCandidate) {
    document.styleEngine().removeStyleSheetCandidateNode(element,
                                                         *insertionPoint);
    m_registeredAsCandidate = false;
  }

  if (m_sheet) {
    clearSheet(element);
    if (element.isConnected()) {
      // TODO(rune@opera.com): resolverChanged() can be removed once stylesheet
      // updates are async. https://crbug.com/567021
      document.styleEngine().resolverChanged(AnalyzedStyleUpdate);
    }
  }
}

StyleElement::ProcessingResult StyleElement::childrenChanged(Element& element) {
  if (m_createdByParser)
    return ProcessingSuccessful;

  return process(element);
}

StyleElement::ProcessingResult StyleElement::finishParsingChildren(
    Element& element) {
  ProcessingResult result = process(element);
  m_createdByParser = false;
  return result;
}

StyleElement::ProcessingResult StyleElement::process(Element& element) {
  if (!element.isConnected())
    return ProcessingSuccessful;
  return createSheet(element, element.textFromChildren());
}

void StyleElement::clearSheet(Element& ownerElement) {
  DCHECK(m_sheet);

  if (m_sheet->isLoading())
    ownerElement.document().styleEngine().removePendingSheet(
        ownerElement, m_styleEngineContext);

  m_sheet.release()->clearOwnerNode();
}

static bool shouldBypassMainWorldCSP(const Element& element) {
  // Main world CSP is bypassed within an isolated world.
  LocalFrame* frame = element.document().frame();
  if (frame && frame->script().shouldBypassMainWorldCSP())
    return true;

  // Main world CSP is bypassed for style elements in user agent shadow DOM.
  ShadowRoot* root = element.containingShadowRoot();
  if (root && root->type() == ShadowRootType::UserAgent)
    return true;

  return false;
}

StyleElement::ProcessingResult StyleElement::createSheet(Element& element,
                                                         const String& text) {
  DCHECK(element.isConnected());
  Document& document = element.document();

  const ContentSecurityPolicy* csp = document.contentSecurityPolicy();
  bool passesContentSecurityPolicyChecks =
      shouldBypassMainWorldCSP(element) ||
      csp->allowStyleWithHash(text, ContentSecurityPolicy::InlineType::Block) ||
      csp->allowInlineStyle(&element, document.url(),
                            element.fastGetAttribute(HTMLNames::nonceAttr),
                            m_startPosition.m_line, text);

  // Clearing the current sheet may remove the cache entry so create the new
  // sheet first
  CSSStyleSheet* newSheet = nullptr;

  // If type is empty or CSS, this is a CSS style sheet.
  const AtomicString& type = this->type();
  if (isCSS(element, type) && passesContentSecurityPolicyChecks) {
    MediaQuerySet* mediaQueries = MediaQuerySet::create(media());

    MediaQueryEvaluator screenEval("screen");
    MediaQueryEvaluator printEval("print");
    if (screenEval.eval(mediaQueries) || printEval.eval(mediaQueries)) {
      m_loading = true;
      TextPosition startPosition =
          m_startPosition == TextPosition::belowRangePosition()
              ? TextPosition::minimumPosition()
              : m_startPosition;
      newSheet = document.styleEngine().createSheet(
          element, text, startPosition, m_styleEngineContext);
      newSheet->setMediaQueries(mediaQueries);
      m_loading = false;
    }
  }

  if (m_sheet)
    clearSheet(element);

  m_sheet = newSheet;
  if (m_sheet)
    m_sheet->contents()->checkLoaded();

  return passesContentSecurityPolicyChecks ? ProcessingSuccessful
                                           : ProcessingFatalError;
}

bool StyleElement::isLoading() const {
  if (m_loading)
    return true;
  return m_sheet ? m_sheet->isLoading() : false;
}

bool StyleElement::sheetLoaded(Document& document) {
  if (isLoading())
    return false;

  document.styleEngine().removePendingSheet(*m_sheet->ownerNode(),
                                            m_styleEngineContext);
  return true;
}

void StyleElement::startLoadingDynamicSheet(Document& document) {
  document.styleEngine().addPendingSheet(m_styleEngineContext);
}

DEFINE_TRACE(StyleElement) {
  visitor->trace(m_sheet);
}

}  // namespace blink