delay_images_filter.h

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/*
 * Copyright 2011 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http:///www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


#ifndef NET_INSTAWEB_REWRITER_PUBLIC_DELAY_IMAGES_FILTER_H_
#define NET_INSTAWEB_REWRITER_PUBLIC_DELAY_IMAGES_FILTER_H_

#include "net/instaweb/rewriter/public/common_filter.h"
#include "net/instaweb/rewriter/public/rewrite_driver.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/string.h"
#include "pagespeed/kernel/base/string_util.h"
#include "pagespeed/kernel/html/html_element.h"
#include "pagespeed/kernel/html/html_filter.h"

namespace net_instaweb {

class Statistics;

class DelayImagesFilter : public CommonFilter {
 public:
  static const char kDelayImagesSuffix[];
  static const char kDelayImagesInlineSuffix[];
  static const char kImageOnloadCode[];
  static const char kImageOnloadJsSnippet[];

  explicit DelayImagesFilter(RewriteDriver* driver);
  virtual ~DelayImagesFilter();

  virtual void StartDocumentImpl();
  virtual void StartElementImpl(HtmlElement* element) { }
  virtual void EndElementImpl(HtmlElement* element);

  virtual void EndDocument();

  virtual const char* Name() const { return "DelayImages"; }

  virtual void DetermineEnabled(GoogleString* disabled_reason);

  static void InitStats(Statistics* statistics);
  static void Terminate();
  ScriptUsage GetScriptUsage() const override { return kWillInjectScripts; }

 private:
  void MaybeAddImageOnloadJsSnippet(HtmlElement* element);

  void InsertLowResImagesAndJs(HtmlElement* element, bool insert_after_element);

  void InsertHighResJs(HtmlElement* element);

  bool ShouldRewriteInplace() const;

  int num_low_res_inlined_images_;
  StringStringMap low_res_data_map_;

  bool insert_low_res_images_inplace_;

  bool lazyload_highres_images_;

  bool is_script_inserted_;

  bool added_image_onload_js_;

  
};

}  

#endif