/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2001 Dirk Mueller (mueller@kde.org)
 *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All
 * rights reserved.
 * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
 * (http://www.torchmobile.com/)
 * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
 * Copyright (C) 2013 Google 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/Fullscreen.h"

#include "bindings/core/v8/ConditionalFeatures.h"
#include "core/dom/Document.h"
#include "core/dom/ElementTraversal.h"
#include "core/dom/StyleEngine.h"
#include "core/dom/TaskRunnerHelper.h"
#include "core/events/Event.h"
#include "core/frame/FrameView.h"
#include "core/frame/HostsUsingFeatures.h"
#include "core/frame/LocalFrame.h"
#include "core/frame/Settings.h"
#include "core/frame/UseCounter.h"
#include "core/html/HTMLIFrameElement.h"
#include "core/input/EventHandler.h"
#include "core/inspector/ConsoleMessage.h"
#include "core/layout/LayoutBlockFlow.h"
#include "core/layout/LayoutFullScreen.h"
#include "core/layout/api/LayoutFullScreenItem.h"
#include "core/page/ChromeClient.h"
#include "core/svg/SVGSVGElement.h"
#include "platform/ScopedOrientationChangeIndicator.h"
#include "platform/UserGestureIndicator.h"

namespace blink {

namespace {

// https://html.spec.whatwg.org/multipage/embedded-content.html#allowed-to-use
bool allowedToUseFullscreen(const Frame* frame) {
  // To determine whether a Document object |document| is allowed to use the
  // feature indicated by attribute name |allowattribute|, run these steps:

  // 1. If |document| has no browsing context, then return false.
  if (!frame)
    return false;

  if (!RuntimeEnabledFeatures::featurePolicyEnabled()) {
    // 2. If |document|'s browsing context is a top-level browsing context, then
    // return true.
    if (frame->isMainFrame())
      return true;

    // 3. If |document|'s browsing context has a browsing context container that
    // is an iframe element with an |allowattribute| attribute specified, and
    // whose node document is allowed to use the feature indicated by
    // |allowattribute|, then return true.
    if (frame->owner() && frame->owner()->allowFullscreen())
      return allowedToUseFullscreen(frame->tree().parent());

    // 4. Return false.
    return false;
  }

  // If Feature Policy is enabled, then we need this hack to support it, until
  // we have proper support for <iframe allowfullscreen> in FP:

  // 1. If FP, by itself, enables fullscreen in this document, then fullscreen
  // is allowed.
  if (frame->securityContext()->getFeaturePolicy()->isFeatureEnabled(
          kFullscreenFeature)) {
    return true;
  }

  // 2. Otherwise, if the embedding frame's document is allowed to use
  // fullscreen (either through FP or otherwise), and either:
  //   a) this is a same-origin embedded document, or
  //   b) this document's iframe has the allowfullscreen attribute set,
  // then fullscreen is allowed.
  if (!frame->isMainFrame()) {
    if (allowedToUseFullscreen(frame->tree().parent())) {
      return (frame->owner() && frame->owner()->allowFullscreen()) ||
             frame->tree()
                 .parent()
                 ->securityContext()
                 ->getSecurityOrigin()
                 ->isSameSchemeHostPortAndSuborigin(
                     frame->securityContext()->getSecurityOrigin());
    }
  }

  // Otherwise, fullscreen is not allowed. (If we reach here and this is the
  // main frame, then fullscreen must have been disabled by FP.)
  return false;
}

bool allowedToRequestFullscreen(Document& document) {
  // An algorithm is allowed to request fullscreen if one of the following is
  // true:

  //  The algorithm is triggered by a user activation.
  if (UserGestureIndicator::utilizeUserGesture())
    return true;

  //  The algorithm is triggered by a user generated orientation change.
  if (ScopedOrientationChangeIndicator::processingOrientationChange()) {
    UseCounter::count(document,
                      UseCounter::FullscreenAllowedByOrientationChange);
    return true;
  }

  String message = ExceptionMessages::failedToExecute(
      "requestFullscreen", "Element",
      "API can only be initiated by a user gesture.");
  document.addConsoleMessage(
      ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));

  return false;
}

// https://fullscreen.spec.whatwg.org/#fullscreen-is-supported
bool fullscreenIsSupported(const Document& document) {
  LocalFrame* frame = document.frame();
  if (!frame)
    return false;

  // Fullscreen is supported if there is no previously-established user
  // preference, security risk, or platform limitation.
  return !document.settings() || document.settings()->getFullscreenSupported();
}

// https://fullscreen.spec.whatwg.org/#fullscreen-element-ready-check
bool fullscreenElementReady(const Element& element) {
  // A fullscreen element ready check for an element |element| returns true if
  // all of the following are true, and false otherwise:

  // |element| is in a document.
  if (!element.isConnected())
    return false;

  // |element|'s node document is allowed to use the feature indicated by
  // attribute name allowfullscreen.
  if (!allowedToUseFullscreen(element.document().frame()))
    return false;

  // |element|'s node document's fullscreen element stack is either empty or its
  // top element is an inclusive ancestor of |element|.
  if (const Element* topElement =
          Fullscreen::fullscreenElementFrom(element.document())) {
    if (!topElement->contains(&element))
      return false;
  }

  // |element| has no ancestor element whose local name is iframe and namespace
  // is the HTML namespace.
  if (Traversal<HTMLIFrameElement>::firstAncestor(element))
    return false;

  // |element|'s node document's browsing context either has a browsing context
  // container and the fullscreen element ready check returns true for
  // |element|'s node document's browsing context's browsing context container,
  // or it has no browsing context container.
  if (const Element* owner = element.document().localOwner()) {
    if (!fullscreenElementReady(*owner))
      return false;
  }

  return true;
}

bool isPrefixed(const AtomicString& type) {
  return type == EventTypeNames::webkitfullscreenchange ||
         type == EventTypeNames::webkitfullscreenerror;
}

Event* createEvent(const AtomicString& type, EventTarget& target) {
  EventInit initializer;
  initializer.setBubbles(isPrefixed(type));
  Event* event = Event::create(type, initializer);
  event->setTarget(&target);
  return event;
}

// Walks the frame tree and returns the first local ancestor frame, if any.
LocalFrame* nextLocalAncestor(Frame& frame) {
  Frame* parent = frame.tree().parent();
  if (!parent)
    return nullptr;
  if (parent->isLocalFrame())
    return toLocalFrame(parent);
  return nextLocalAncestor(*parent);
}

// Walks the document's frame tree and returns the document of the first local
// ancestor frame, if any.
Document* nextLocalAncestor(Document& document) {
  LocalFrame* frame = document.frame();
  if (!frame)
    return nullptr;
  LocalFrame* next = nextLocalAncestor(*document.frame());
  if (!next)
    return nullptr;
  DCHECK(next->document());
  return next->document();
}

// Helper to walk the ancestor chain and return the Document of the topmost
// local ancestor frame. Note that this is not the same as the topmost frame's
// Document, which might be unavailable in OOPIF scenarios. For example, with
// OOPIFs, when called on the bottom frame's Document in a A-B-C-B hierarchy in
// process B, this will skip remote frame C and return this frame: A-[B]-C-B.
Document& topmostLocalAncestor(Document& document) {
  if (Document* next = nextLocalAncestor(document))
    return topmostLocalAncestor(*next);
  return document;
}

// Helper to find the browsing context container in |doc| that embeds the
// |descendant| Document, possibly through multiple levels of nesting.  This
// works even in OOPIF scenarios like A-B-A, where there may be remote frames
// in between |doc| and |descendant|.
HTMLFrameOwnerElement* findContainerForDescendant(const Document& doc,
                                                  const Document& descendant) {
  Frame* frame = descendant.frame();
  while (frame->tree().parent() != doc.frame())
    frame = frame->tree().parent();
  return toHTMLFrameOwnerElement(frame->owner());
}

// Fullscreen status affects scroll paint properties through
// FrameView::userInputScrollable().
void setNeedsPaintPropertyUpdate(Document* document) {
  if (!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() ||
      RuntimeEnabledFeatures::rootLayerScrollingEnabled())
    return;

  if (!document)
    return;

  LocalFrame* frame = document->frame();
  if (!frame)
    return;

  if (FrameView* frameView = frame->view())
    frameView->setNeedsPaintPropertyUpdate();
}

}  // anonymous namespace

const char* Fullscreen::supplementName() {
  return "Fullscreen";
}

Fullscreen& Fullscreen::from(Document& document) {
  Fullscreen* fullscreen = fromIfExists(document);
  if (!fullscreen) {
    fullscreen = new Fullscreen(document);
    Supplement<Document>::provideTo(document, supplementName(), fullscreen);
  }

  return *fullscreen;
}

Fullscreen* Fullscreen::fromIfExistsSlow(Document& document) {
  return static_cast<Fullscreen*>(
      Supplement<Document>::from(document, supplementName()));
}

Element* Fullscreen::fullscreenElementFrom(Document& document) {
  if (Fullscreen* found = fromIfExists(document))
    return found->fullscreenElement();
  return nullptr;
}

Element* Fullscreen::fullscreenElementForBindingFrom(TreeScope& scope) {
  Element* element = fullscreenElementFrom(scope.document());
  if (!element || !RuntimeEnabledFeatures::fullscreenUnprefixedEnabled())
    return element;

  // TODO(kochi): Once V0 code is removed, we can use the same logic for
  // Document and ShadowRoot.
  if (!scope.rootNode().isShadowRoot()) {
    // For Shadow DOM V0 compatibility: We allow returning an element in V0
    // shadow tree, even though it leaks the Shadow DOM.
    if (element->isInV0ShadowTree()) {
      UseCounter::count(scope.document(),
                        UseCounter::DocumentFullscreenElementInV0Shadow);
      return element;
    }
  } else if (!toShadowRoot(scope.rootNode()).isV1()) {
    return nullptr;
  }
  return scope.adjustedElement(*element);
}

Element* Fullscreen::currentFullScreenElementFrom(Document& document) {
  if (Fullscreen* found = fromIfExists(document))
    return found->currentFullScreenElement();
  return nullptr;
}

Element* Fullscreen::currentFullScreenElementForBindingFrom(
    Document& document) {
  Element* element = currentFullScreenElementFrom(document);
  if (!element || !RuntimeEnabledFeatures::fullscreenUnprefixedEnabled())
    return element;

  // For Shadow DOM V0 compatibility: We allow returning an element in V0 shadow
  // tree, even though it leaks the Shadow DOM.
  if (element->isInV0ShadowTree()) {
    UseCounter::count(document,
                      UseCounter::DocumentFullscreenElementInV0Shadow);
    return element;
  }
  return document.adjustedElement(*element);
}

Fullscreen::Fullscreen(Document& document)
    : Supplement<Document>(document),
      ContextLifecycleObserver(&document),
      m_fullScreenLayoutObject(nullptr),
      m_eventQueueTimer(TaskRunnerHelper::get(TaskType::Unthrottled, &document),
                        this,
                        &Fullscreen::eventQueueTimerFired),
      m_forCrossProcessDescendant(false) {
  document.setHasFullscreenSupplement();
}

Fullscreen::~Fullscreen() {}

inline Document* Fullscreen::document() {
  return toDocument(lifecycleContext());
}

void Fullscreen::contextDestroyed(ExecutionContext*) {
  m_eventQueue.clear();

  if (m_fullScreenLayoutObject)
    m_fullScreenLayoutObject->destroy();

  m_currentFullScreenElement = nullptr;
  m_fullscreenElementStack.clear();
}

// https://fullscreen.spec.whatwg.org/#dom-element-requestfullscreen
void Fullscreen::requestFullscreen(Element& element) {
  // TODO(foolip): Make RequestType::Unprefixed the default when the unprefixed
  // API is enabled. https://crbug.com/383813
  requestFullscreen(element, RequestType::Prefixed, false);
}

void Fullscreen::requestFullscreen(Element& element,
                                   RequestType requestType,
                                   bool forCrossProcessDescendant) {
  Document& document = element.document();

  // Use counters only need to be incremented in the process of the actual
  // fullscreen element.
  if (!forCrossProcessDescendant) {
    if (document.isSecureContext()) {
      UseCounter::count(document, UseCounter::FullscreenSecureOrigin);
    } else {
      UseCounter::count(document, UseCounter::FullscreenInsecureOrigin);
      HostsUsingFeatures::countAnyWorld(
          document, HostsUsingFeatures::Feature::FullscreenInsecureHost);
    }
  }

  // Ignore this call if the document is not in a live frame.
  if (!document.isActive() || !document.frame())
    return;

  // If |element| is on top of |doc|'s fullscreen element stack, terminate these
  // substeps.
  if (&element == fullscreenElementFrom(document))
    return;

  do {
    // 1. If any of the following conditions are false, then terminate these
    // steps and queue a task to fire an event named fullscreenerror with its
    // bubbles attribute set to true on the context object's node document:

    // |element|'s namespace is the HTML namespace or |element| is an SVG
    // svg or MathML math element.
    // Note: MathML is not supported.
    if (!element.isHTMLElement() && !isSVGSVGElement(element))
      break;

    // The fullscreen element ready check for |element| returns true.
    if (!fullscreenElementReady(element))
      break;

    // Fullscreen is supported.
    if (!fullscreenIsSupported(document))
      break;

    // This algorithm is allowed to request fullscreen.
    // OOPIF: If |forCrossProcessDescendant| is true, requestFullscreen was
    // already called on a descendant element in another process, and
    // getting here means that it was already allowed to request fullscreen.
    if (!forCrossProcessDescendant && !allowedToRequestFullscreen(document))
      break;

    // 2. Let doc be element's node document. (i.e. "this")

    // 3. Let docs be all doc's ancestor browsing context's documents (if any)
    // and doc.
    //
    // For OOPIF scenarios, |docs| will only contain documents for local
    // ancestors, and remote ancestors will be processed in their
    // respective processes.  This preserves the spec's event firing order
    // for local ancestors, but not for remote ancestors.  However, that
    // difference shouldn't be observable in practice: a fullscreenchange
    // event handler would need to postMessage a frame in another renderer
    // process, where the message should be queued up and processed after
    // the IPC that dispatches fullscreenchange.
    HeapDeque<Member<Document>> docs;
    for (Document* doc = &document; doc; doc = nextLocalAncestor(*doc))
      docs.prepend(doc);

    // 4. For each document in docs, run these substeps:
    HeapDeque<Member<Document>>::iterator current = docs.begin(),
                                          following = docs.begin();

    do {
      ++following;

      // 1. Let following document be the document after document in docs, or
      // null if there is no such document.
      Document* currentDoc = *current;
      Document* followingDoc = following != docs.end() ? *following : nullptr;

      // 2. If following document is null, push context object on document's
      // fullscreen element stack, and queue a task to fire an event named
      // fullscreenchange with its bubbles attribute set to true on the
      // document.
      if (!followingDoc) {
        from(*currentDoc).pushFullscreenElementStack(element, requestType);
        from(document).enqueueChangeEvent(*currentDoc, requestType);
        continue;
      }

      // 3. Otherwise, if document's fullscreen element stack is either empty or
      // its top element is not following document's browsing context container,
      Element* topElement = fullscreenElementFrom(*currentDoc);
      HTMLFrameOwnerElement* followingOwner =
          findContainerForDescendant(*currentDoc, *followingDoc);
      if (!topElement || topElement != followingOwner) {
        // ...push following document's browsing context container on document's
        // fullscreen element stack, and queue a task to fire an event named
        // fullscreenchange with its bubbles attribute set to true on document.
        from(*currentDoc)
            .pushFullscreenElementStack(*followingOwner, requestType);
        from(document).enqueueChangeEvent(*currentDoc, requestType);
        continue;
      }

      // 4. Otherwise, do nothing for this document. It stays the same.
    } while (++current != docs.end());

    from(document).m_forCrossProcessDescendant = forCrossProcessDescendant;

    // 5. Return, and run the remaining steps asynchronously.
    // 6. Optionally, perform some animation.
    from(document).m_pendingFullscreenElement = &element;
    document.frame()->chromeClient().enterFullscreen(*document.frame());

    // 7. Optionally, display a message indicating how the user can exit
    // displaying the context object fullscreen.
    return;
  } while (false);

  from(document).enqueueErrorEvent(element, requestType);
}

// https://fullscreen.spec.whatwg.org/#fully-exit-fullscreen
void Fullscreen::fullyExitFullscreen(Document& document) {
  // To fully exit fullscreen, run these steps:

  // 1. Let |doc| be the top-level browsing context's document.
  //
  // Since the top-level browsing context's document might be unavailable in
  // OOPIF scenarios (i.e., when the top frame is remote), this actually uses
  // the Document of the topmost local ancestor frame.  Without OOPIF, this
  // will be the top frame's document.  With OOPIF, each renderer process for
  // the current page will separately call fullyExitFullscreen to cover all
  // local frames in each process.
  Document& doc = topmostLocalAncestor(document);

  // 2. If |doc|'s fullscreen element stack is empty, terminate these steps.
  if (!fullscreenElementFrom(doc))
    return;

  // 3. Remove elements from |doc|'s fullscreen element stack until only the top
  // element is left.
  size_t stackSize = from(doc).m_fullscreenElementStack.size();
  from(doc).m_fullscreenElementStack.remove(0, stackSize - 1);
  DCHECK_EQ(from(doc).m_fullscreenElementStack.size(), 1u);

  // 4. Act as if the exitFullscreen() method was invoked on |doc|.
  exitFullscreen(doc);
}

// https://fullscreen.spec.whatwg.org/#exit-fullscreen
void Fullscreen::exitFullscreen(Document& document) {
  // The exitFullscreen() method must run these steps:

  // Ignore this call if the document is not in a live frame.
  if (!document.isActive() || !document.frame())
    return;

  // 1. Let doc be the context object. (i.e. "this")
  // 2. If doc's fullscreen element stack is empty, terminate these steps.
  if (!fullscreenElementFrom(document))
    return;

  // 3. Let descendants be all the doc's descendant browsing context's documents
  // with a non-empty fullscreen element stack (if any), ordered so that the
  // child of the doc is last and the document furthest away from the doc is
  // first.
  HeapDeque<Member<Document>> descendants;
  for (Frame* descendant = document.frame()->tree().traverseNext(); descendant;
       descendant = descendant->tree().traverseNext()) {
    if (!descendant->isLocalFrame())
      continue;
    DCHECK(toLocalFrame(descendant)->document());
    if (fullscreenElementFrom(*toLocalFrame(descendant)->document()))
      descendants.prepend(toLocalFrame(descendant)->document());
  }

  // 4. For each descendant in descendants, empty descendant's fullscreen
  // element stack, and queue a task to fire an event named fullscreenchange
  // with its bubbles attribute set to true on descendant.
  for (auto& descendant : descendants) {
    DCHECK(descendant);
    RequestType requestType =
        from(*descendant).m_fullscreenElementStack.back().second;
    from(*descendant).clearFullscreenElementStack();
    from(document).enqueueChangeEvent(*descendant, requestType);
  }

  // 5. While doc is not null, run these substeps:
  Element* newTop = nullptr;
  for (Document* currentDoc = &document; currentDoc;) {
    RequestType requestType =
        from(*currentDoc).m_fullscreenElementStack.back().second;

    // 1. Pop the top element of doc's fullscreen element stack.
    from(*currentDoc).popFullscreenElementStack();

    //    If doc's fullscreen element stack is non-empty and the element now at
    //    the top is either not in a document or its node document is not doc,
    //    repeat this substep.
    newTop = fullscreenElementFrom(*currentDoc);
    if (newTop && (!newTop->isConnected() || newTop->document() != currentDoc))
      continue;

    // 2. Queue a task to fire an event named fullscreenchange with its bubbles
    // attribute set to true on doc.
    from(document).enqueueChangeEvent(*currentDoc, requestType);

    // 3. If doc's fullscreen element stack is empty and doc's browsing context
    // has a browsing context container, set doc to that browsing context
    // container's node document.
    //
    // OOPIF: If browsing context container's document is in another
    // process, keep moving up the ancestor chain and looking for a
    // browsing context container with a local document.
    // TODO(alexmos): Deal with nested fullscreen cases, see
    // https://crbug.com/617369.
    if (!newTop) {
      currentDoc = nextLocalAncestor(*currentDoc);
      continue;
    }

    // 4. Otherwise, set doc to null.
    currentDoc = nullptr;
  }

  // 6. Return, and run the remaining steps asynchronously.
  // 7. Optionally, perform some animation.

  // Only exit fullscreen mode if the fullscreen element stack is empty.
  if (!newTop) {
    document.frame()->chromeClient().exitFullscreen(*document.frame());
    return;
  }

  // Otherwise, enter fullscreen for the fullscreen element stack's top element.
  from(document).m_pendingFullscreenElement = newTop;
  from(document).didEnterFullscreen();
}

// https://fullscreen.spec.whatwg.org/#dom-document-fullscreenenabled
bool Fullscreen::fullscreenEnabled(Document& document) {
  // The fullscreenEnabled attribute's getter must return true if the context
  // object is allowed to use the feature indicated by attribute name
  // allowfullscreen and fullscreen is supported, and false otherwise.
  return allowedToUseFullscreen(document.frame()) &&
         fullscreenIsSupported(document);
}

void Fullscreen::didEnterFullscreen() {
  if (!document()->isActive() || !document()->frame())
    return;

  // Start the timer for events enqueued by |requestFullscreen()|. The hover
  // state update is scheduled first so that it's done when the events fire.
  document()->frame()->eventHandler().scheduleHoverStateUpdate();
  m_eventQueueTimer.startOneShot(0, BLINK_FROM_HERE);

  Element* element = m_pendingFullscreenElement.release();
  if (!element)
    return;

  if (m_currentFullScreenElement == element)
    return;

  if (!element->isConnected() || &element->document() != document()) {
    // The element was removed or has moved to another document since the
    // |requestFullscreen()| call. Exit fullscreen again to recover.
    // TODO(foolip): Fire a fullscreenerror event. This is currently difficult
    // because the fullscreenchange event has already been enqueued and possibly
    // even fired. https://crbug.com/402376
    LocalFrame& frame = *document()->frame();
    frame.chromeClient().exitFullscreen(frame);
    return;
  }

  if (m_fullScreenLayoutObject)
    m_fullScreenLayoutObject->unwrapLayoutObject();

  Element* previousElement = m_currentFullScreenElement;
  m_currentFullScreenElement = element;

  // Create a placeholder block for a the full-screen element, to keep the page
  // from reflowing when the element is removed from the normal flow. Only do
  // this for a LayoutBox, as only a box will have a frameRect. The placeholder
  // will be created in setFullScreenLayoutObject() during layout.
  LayoutObject* layoutObject = m_currentFullScreenElement->layoutObject();
  bool shouldCreatePlaceholder = layoutObject && layoutObject->isBox();
  if (shouldCreatePlaceholder) {
    m_savedPlaceholderFrameRect = toLayoutBox(layoutObject)->frameRect();
    m_savedPlaceholderComputedStyle =
        ComputedStyle::clone(layoutObject->styleRef());
  }

  // TODO(alexmos): When |m_forCrossProcessDescendant| is true, some of
  // this layout work has already been done in another process, so it should
  // not be necessary to repeat it here.
  if (m_currentFullScreenElement != document()->documentElement()) {
    LayoutFullScreen::wrapLayoutObject(
        layoutObject, layoutObject ? layoutObject->parent() : 0, document());
  }

  // When |m_forCrossProcessDescendant| is true, m_currentFullScreenElement
  // corresponds to the HTMLFrameOwnerElement for the out-of-process iframe
  // that contains the actual fullscreen element.   Hence, it must also set
  // the ContainsFullScreenElement flag (so that it gains the
  // -webkit-full-screen-ancestor style).
  if (m_forCrossProcessDescendant) {
    DCHECK(m_currentFullScreenElement->isFrameOwnerElement());
    DCHECK(toHTMLFrameOwnerElement(m_currentFullScreenElement)
               ->contentFrame()
               ->isRemoteFrame());
    m_currentFullScreenElement->setContainsFullScreenElement(true);
  }

  m_currentFullScreenElement
      ->setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(true);

  document()->styleEngine().ensureUAStyleForFullscreen();
  m_currentFullScreenElement->pseudoStateChanged(CSSSelector::PseudoFullScreen);

  // FIXME: This should not call updateStyleAndLayoutTree.
  document()->updateStyleAndLayoutTree();

  document()->frame()->chromeClient().fullscreenElementChanged(previousElement,
                                                               element);
}

void Fullscreen::didExitFullscreen() {
  if (!document()->isActive() || !document()->frame())
    return;

  // Start the timer for events enqueued by |exitFullscreen()|. The hover state
  // update is scheduled first so that it's done when the events fire.
  document()->frame()->eventHandler().scheduleHoverStateUpdate();
  m_eventQueueTimer.startOneShot(0, BLINK_FROM_HERE);

  // If fullscreen was canceled by the browser, e.g. if the user pressed Esc,
  // then |exitFullscreen()| was never called. Let |fullyExitFullscreen()| clear
  // the fullscreen element stack and fire any events as necessary.
  // TODO(foolip): Remove this when state changes and events are synchronized
  // with animation frames. https://crbug.com/402376
  fullyExitFullscreen(*document());

  if (!m_currentFullScreenElement)
    return;

  if (m_forCrossProcessDescendant)
    m_currentFullScreenElement->setContainsFullScreenElement(false);

  m_currentFullScreenElement
      ->setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(false);

  if (m_fullScreenLayoutObject)
    LayoutFullScreenItem(m_fullScreenLayoutObject).unwrapLayoutObject();

  document()->styleEngine().ensureUAStyleForFullscreen();
  m_currentFullScreenElement->pseudoStateChanged(CSSSelector::PseudoFullScreen);
  Element* previousElement = m_currentFullScreenElement;
  m_currentFullScreenElement = nullptr;

  m_forCrossProcessDescendant = false;

  document()->frame()->chromeClient().fullscreenElementChanged(previousElement,
                                                               nullptr);
}

void Fullscreen::setFullScreenLayoutObject(LayoutFullScreen* layoutObject) {
  if (layoutObject == m_fullScreenLayoutObject)
    return;

  if (layoutObject && m_savedPlaceholderComputedStyle) {
    layoutObject->createPlaceholder(std::move(m_savedPlaceholderComputedStyle),
                                    m_savedPlaceholderFrameRect);
  } else if (layoutObject && m_fullScreenLayoutObject &&
             m_fullScreenLayoutObject->placeholder()) {
    LayoutBlockFlow* placeholder = m_fullScreenLayoutObject->placeholder();
    layoutObject->createPlaceholder(
        ComputedStyle::clone(placeholder->styleRef()),
        placeholder->frameRect());
  }

  if (m_fullScreenLayoutObject)
    m_fullScreenLayoutObject->unwrapLayoutObject();
  DCHECK(!m_fullScreenLayoutObject);

  m_fullScreenLayoutObject = layoutObject;
}

void Fullscreen::fullScreenLayoutObjectDestroyed() {
  m_fullScreenLayoutObject = nullptr;
}

void Fullscreen::enqueueChangeEvent(Document& document,
                                    RequestType requestType) {
  Event* event;
  if (requestType == RequestType::Unprefixed) {
    event = createEvent(EventTypeNames::fullscreenchange, document);
  } else {
    DCHECK(document.hasFullscreenSupplement());
    Fullscreen& fullscreen = from(document);
    EventTarget* target = fullscreen.fullscreenElement();
    if (!target)
      target = fullscreen.currentFullScreenElement();
    if (!target)
      target = &document;
    event = createEvent(EventTypeNames::webkitfullscreenchange, *target);
  }
  m_eventQueue.append(event);
  // NOTE: The timer is started in didEnterFullscreen/didExitFullscreen.
}

void Fullscreen::enqueueErrorEvent(Element& element, RequestType requestType) {
  Event* event;
  if (requestType == RequestType::Unprefixed)
    event = createEvent(EventTypeNames::fullscreenerror, element.document());
  else
    event = createEvent(EventTypeNames::webkitfullscreenerror, element);
  m_eventQueue.append(event);
  m_eventQueueTimer.startOneShot(0, BLINK_FROM_HERE);
}

void Fullscreen::eventQueueTimerFired(TimerBase*) {
  HeapDeque<Member<Event>> eventQueue;
  m_eventQueue.swap(eventQueue);

  while (!eventQueue.isEmpty()) {
    Event* event = eventQueue.takeFirst();
    Node* target = event->target()->toNode();

    // If the element was removed from our tree, also message the
    // documentElement.
    if (!target->isConnected() && document()->documentElement()) {
      DCHECK(isPrefixed(event->type()));
      eventQueue.append(
          createEvent(event->type(), *document()->documentElement()));
    }

    target->dispatchEvent(event);
  }
}

void Fullscreen::elementRemoved(Element& oldNode) {
  // Whenever the removing steps run with an |oldNode| and |oldNode| is in its
  // node document's fullscreen element stack, run these steps:

  // 1. If |oldNode| is at the top of its node document's fullscreen element
  // stack, act as if the exitFullscreen() method was invoked on that document.
  if (fullscreenElement() == &oldNode) {
    exitFullscreen(oldNode.document());
    return;
  }

  // 2. Otherwise, remove |oldNode| from its node document's fullscreen element
  // stack.
  for (size_t i = 0; i < m_fullscreenElementStack.size(); ++i) {
    if (m_fullscreenElementStack[i].first.get() == &oldNode) {
      m_fullscreenElementStack.remove(i);
      return;
    }
  }

  // NOTE: |oldNode| was not in the fullscreen element stack.
}

void Fullscreen::clearFullscreenElementStack() {
  if (m_fullscreenElementStack.isEmpty())
    return;

  m_fullscreenElementStack.clear();

  setNeedsPaintPropertyUpdate(document());
}

void Fullscreen::popFullscreenElementStack() {
  if (m_fullscreenElementStack.isEmpty())
    return;

  m_fullscreenElementStack.pop_back();

  setNeedsPaintPropertyUpdate(document());
}

void Fullscreen::pushFullscreenElementStack(Element& element,
                                            RequestType requestType) {
  m_fullscreenElementStack.push_back(std::make_pair(&element, requestType));

  setNeedsPaintPropertyUpdate(document());
}

DEFINE_TRACE(Fullscreen) {
  visitor->trace(m_pendingFullscreenElement);
  visitor->trace(m_fullscreenElementStack);
  visitor->trace(m_currentFullScreenElement);
  visitor->trace(m_eventQueue);
  Supplement<Document>::trace(visitor);
  ContextLifecycleObserver::trace(visitor);
}

}  // namespace blink