Chromium 在WebContents中添加自定义数据c++

为了能在WebContents中添加自定义数据先看下几个关键类的介绍。

一、WebContents 介绍:

WebContents是content模块核心,是呈现 Web 内容(通常为 HTML)位于矩形区域中。

最直观的是一个浏览器标签对应一个WebContents,里面加载一个网页等。

二、看下WebContents定义:

content\public\browser\web_contents.h

{

WebContents具体实现在:

content\browser\web_contents\web_contents_impl.cc

content\browser\web_contents\web_contents_impl.h

}

WebContents继承自base::SupportsUserData

cpp 复制代码
// WebContents is the core class in content/. A WebContents renders web content
// (usually HTML) in a rectangular area.
//
// Instantiating one is simple:
//   std::unique_ptr<content::WebContents> web_contents(
//       content::WebContents::Create(
//           content::WebContents::CreateParams(browser_context)));
//   gfx::NativeView view = web_contents->GetNativeView();
//   // |view| is an HWND, NSView*, etc.; insert it into the view hierarchy
//   // wherever it needs to go.
//
// That's it; go to your kitchen, grab a scone, and chill. WebContents will do
// all the multi-process stuff behind the scenes. More details are at
// https://www.chromium.org/developers/design-documents/multi-process-architecture
// .
//
// The owner of `std::unique_ptr<content::WebContents> web_contents` is
// responsible for ensuring that `web_contents` are destroyed (e.g. closed)
// *before* the corresponding `browser_context` is destroyed.
//
// Each WebContents has a `NavigationController`, which can be obtained from
// `GetController()`, and is used to load URLs into the WebContents, navigate
// it backwards/forwards, etc.
// See navigation_controller.h for more details.
class WebContents : public PageNavigator,
                    public base::SupportsUserData {
  // Do not remove this macro!
  // The macro is maintained by the memory safety team.
  ADVANCED_MEMORY_SAFETY_CHECKS();

 public:
  struct CONTENT_EXPORT CreateParams {
    explicit CreateParams(
        BrowserContext* context,
        base::Location creator_location = base::Location::Current());
    CreateParams(BrowserContext* context,
                 scoped_refptr<SiteInstance> site,
                 base::Location creator_location = base::Location::Current());
    CreateParams(const CreateParams& other);
    ~CreateParams();
..................................
};

三、base::SupportsUserData定义:

base\supports_user_data.h

注意:看下这几个方法:

Data* GetUserData(const void* key) const;

[[nodiscard]] std::unique_ptr<Data> TakeUserData(const void* key);

void SetUserData(const void* key, std::unique_ptr<Data> data);

void RemoveUserData(const void* key);

cpp 复制代码
namespace base {

// This is a helper for classes that want to allow users to stash random data by
// key. At destruction all the objects will be destructed.
class BASE_EXPORT SupportsUserData {
 public:
  SupportsUserData();
  SupportsUserData(SupportsUserData&&);
  SupportsUserData& operator=(SupportsUserData&&);
  SupportsUserData(const SupportsUserData&) = delete;
  SupportsUserData& operator=(const SupportsUserData&) = delete;

  // Derive from this class and add your own data members to associate extra
  // information with this object. Alternatively, add this as a public base
  // class to any class with a virtual destructor.
  class BASE_EXPORT Data {
   public:
    virtual ~Data() = default;

    // Returns a copy of |this|; null if copy is not supported.
    virtual std::unique_ptr<Data> Clone();
  };

  // The user data allows the clients to associate data with this object.
  // |key| must not be null--that value is too vulnerable for collision.
  // NOTE: SetUserData() with an empty unique_ptr behaves the same as
  // RemoveUserData().
  Data* GetUserData(const void* key) const;
  [[nodiscard]] std::unique_ptr<Data> TakeUserData(const void* key);
  void SetUserData(const void* key, std::unique_ptr<Data> data);
  void RemoveUserData(const void* key);

  // Adds all data from |other|, that is clonable, to |this|. That is, this
  // iterates over the data in |other|, and any data that returns non-null from
  // Clone() is added to |this|.
  void CloneDataFrom(const SupportsUserData& other);

  // SupportsUserData is not thread-safe, and on debug build will assert it is
  // only used on one execution sequence. Calling this method allows the caller
  // to hand the SupportsUserData instance across execution sequences. Use only
  // if you are taking full control of the synchronization of that hand over.
  void DetachFromSequence();

 protected:
  virtual ~SupportsUserData();

  // Clear all user data from this object. This can be used if the subclass
  // needs to provide reset functionality.
  void ClearAllUserData();

 private:
  // Externally-defined data accessible by key.
  absl::flat_hash_map<const void*, std::unique_ptr<Data>> user_data_;
  bool in_destructor_ = false;
  // Guards usage of |user_data_|
  SEQUENCE_CHECKER(sequence_checker_);
};

// Adapter class that releases a refcounted object when the
// SupportsUserData::Data object is deleted.
template <typename T>
class UserDataAdapter : public SupportsUserData::Data {
 public:
  static T* Get(const SupportsUserData* supports_user_data, const void* key) {
    UserDataAdapter* data =
      static_cast<UserDataAdapter*>(supports_user_data->GetUserData(key));
    return data ? static_cast<T*>(data->object_.get()) : nullptr;
  }

  explicit UserDataAdapter(T* object) : object_(object) {}
  UserDataAdapter(const UserDataAdapter&) = delete;
  UserDataAdapter& operator=(const UserDataAdapter&) = delete;
  ~UserDataAdapter() override = default;

  T* release() { return object_.release(); }

 private:
  scoped_refptr<T> const object_;
};

}  // namespace base

四、在WebContents添加数据定义:

由于WebContents继承自base::SupportsUserData,所以只需要调用

base::SupportsUserData::SetUserData 方法即可。

1、需要定义一个类AwSettingsUserData 继承自base::SupportsUserData::Data

cpp 复制代码
class AwSettingsUserData : public base::SupportsUserData::Data {

 public:

  //添加自己的数据

 private:


};

2、base::SupportsUserData::SetUserData设置数据:

web_contents->SetUserData(kAwSettingsUserDataKey,

std::make_unique<AwSettingsUserData>(this));

3、base::SupportsUserData::GetUserData获取数据:

AwSettingsUserData* data = static_cast<AwSettingsUserData*>(

web_contents->GetUserData(kAwSettingsUserDataKey));

总结:至此在WebContents添加自定义数据方法介绍完毕。

添加自定义数据主要是为了标记WebContents 可以根据此标记对标签进行特殊处理。

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