lazyload_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_LAZYLOAD_IMAGES_FILTER_H_
#define NET_INSTAWEB_REWRITER_PUBLIC_LAZYLOAD_IMAGES_FILTER_H_

#include "net/instaweb/rewriter/public/common_filter.h"
#include "net/instaweb/rewriter/public/rewrite_driver.h"
#include "net/instaweb/rewriter/public/rewrite_options.h"
#include "pagespeed/kernel/base/string.h"
#include "pagespeed/kernel/html/html_element.h"
#include "pagespeed/kernel/html/html_filter.h"
#include "pagespeed/opt/logging/enums.pb.h"

namespace net_instaweb {

class StaticAssetManager;
class Statistics;

class LazyloadImagesFilter : public CommonFilter {
 public:
  static const char* kImageLazyloadCode;
  static const char* kImageOnloadCode;
  static const char* kLoadAllImages;
  static const char* kOverrideAttributeFunctions;
  static const char* kIsLazyloadScriptInsertedPropertyName;

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

  virtual const char* Name() const { return "Lazyload Images"; }
  ScriptUsage GetScriptUsage() const override { return kWillInjectScripts; }

  static void InitStats(Statistics* statistics);
  static void Terminate();

  static RewriterHtmlApplication::Status ShouldApply(RewriteDriver* driver);
  static GoogleString GetLazyloadJsSnippet(
      const RewriteOptions* options,
      StaticAssetManager* static_asset_manager);

 private:
  virtual void StartDocumentImpl();
  virtual void EndDocument();
  virtual void StartElementImpl(HtmlElement* element);
  virtual void EndElementImpl(HtmlElement* element);
  virtual void DetermineEnabled(GoogleString* disabled_reason);

  void Clear();

  static GoogleString GetBlankImageSrc(
      const RewriteOptions* options,
      const StaticAssetManager* static_asset_manager);

  void InsertLazyloadJsCode(HtmlElement* element);

  void InsertOverrideAttributesScript(HtmlElement* element,
                                      bool is_before_script);

  GoogleString blank_image_url_;
  HtmlElement* skip_rewrite_;
  HtmlElement* head_element_;
  bool main_script_inserted_;
  bool abort_rewrite_;
  bool abort_script_inserted_;
  int num_images_lazily_loaded_;
};

}  

#endif