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

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "config.h"
   6 #include "core/dom/DocumentVisibilityObserver.h"
   7
   8 #include "core/dom/Document.h"
   9
  10 namespace blink {
  11
  12 DocumentVisibilityObserver::DocumentVisibilityObserver(Document& document)
  13     : m_document(nullptr)
  14 {
  15     registerObserver(document);
  16 }
  17
  18 DocumentVisibilityObserver::~DocumentVisibilityObserver()
  19 {
  20 #if !ENABLE(OILPAN)
  21     unregisterObserver();
  22 #endif
  23 }
  24
  25 DEFINE_TRACE(DocumentVisibilityObserver)
  26 {
  27     visitor->trace(m_document);
  28 }
  29
  30 void DocumentVisibilityObserver::unregisterObserver()
  31 {
  32     if (m_document) {
  33         m_document->unregisterVisibilityObserver(this);
  34         m_document = nullptr;
  35     }
  36 }
  37
  38 void DocumentVisibilityObserver::registerObserver(Document& document)
  39 {
  40     ASSERT(!m_document);
  41     m_document = &document;
  42     if (m_document)
  43         m_document->registerVisibilityObserver(this);
  44 }
  45
  46 void DocumentVisibilityObserver::setObservedDocument(Document& document)
  47 {
  48     unregisterObserver();
  49     registerObserver(document);
  50 }
  51
  52 } // namespace blink