CEF3开发者系列之单进程模式应用

本文基于cef_binary_3.2623.1401.gb90a3be_windows32 ，即Chromium 49。主要利用CEF3在Windows动态链接库dll中做一些辅助性界面开发。

需要解决的问题：

1、 使用单进程。由于项目是给第三方程序调用的SDK，所以不能使用多进程模式，否则增加对接成本和进程控制成本。

2、 JS与Native互调。某些界面中有前端JS与客户端Native互相调用的接口。

在CEF3中使用单进程比较简单，在初始化CEF3的时候，通过CefSettings配置进程模式。

CefSettings settings;
settings.single_process = true;        //采用单进程模式
settings.single_process = false;        //采用多进程模式

先来简单的带一笔CEF3的进程模式介绍：

CEF3是多进程架构的。Browser被定义为主进程，负责窗口管理，界面绘制和网络交互。Blink的渲染和Js的执行被放在一个独立的Render 进程中；除此之外，Render进程还负责Js Binding和对Dom节点的访问。 默认的进程模型中，会为每个标签页创建一个新的Render进程。其他进程按需创建，例如管理插件的进程以及处理合成加速的进程等都是按需创建。

默认情况下，主应用程序会被多次启动运行各自独立的进程。这是通过传递不同的命令行参数给CefExecuteProcess函数做到的。

  int exit_code = CefExecuteProcess(main_args, NULL, sandbox_info);
  if (exit_code >= 0) {
    // The sub-process has completed so return here.
    return exit_code;
  }

Browser和Render进程可以通过发送异步消息进行双向通信。甚至在Render进程可以注册在Browser进程响应的异步JavaScript API。

single_process 设置为true时，Browser和Renderer使用一个进程。此项也可以通过命令行参数“single-process”配置。

回到我们需要解决的问题：单进程模式的时候，Browser和Renderer使用一个进程，不仅满足界面的绘制，同时满足JS的执行，与Native进行互相调用。正好满足的我们的需求，幸好我们暂时不需要加载插件。

解决了方案和技术原理性问题，剩下的基本上就是编写代码了。

基于CEF3框架实现一个页面加载，需要在初始化中实现CefBrowserProcessHandler和CefRenderProcessHandler类以及浏览器显示、加载、生命周期等回调类。

初始化如下：

// Structure for passing command-line arguments.
  // The definition of this structure is platform-specific.
  CefMainArgs main_args(argc, argv);

  // Optional implementation of the CefApp interface.
  CefRefPtr<MyClentApp> app(new MyClentApp);

  // Execute the sub-process logic, if any. This will either return immediately for the browser
  // process or block until the sub-process should exit.
  int exit_code = CefExecuteProcess(main_args, app.get());
  if (exit_code >= 0) {
    // The sub-process terminated, exit now.
    return exit_code;
  }
  scoped_ptr<MainContextImpl>  mainContext.reset(new MainContextImpl(command_line, NULL));
  // Populate this structure to customize CEF behavior.
  CefSettings settings;
  mainContext->PopulateSettings(&settings);
  settings.single_process = true;
  // Initialize CEF in the main process.
  CefInitialize(main_args, settings, app.get());

  // Run the CEF message loop. This will block until CefQuitMessageLoop() is called.
  CefRunMessageLoop();

  // Shut down CEF.
  CefShutdown();

 

MyClientApp主要集成CefBrowserProcessHandler和CefRequestContextHandler 实现页面加载、渲染和JS执行等

下边代码是头文件代码，具体的实现方式，参照CEF3的实例cefclient中ClientAppBrowser和 ClientAppRenderer。另外JS桥接口的调用，通过自定义实现CefV8Handler。在Renderer中的OnWebKitInitialized中注册桥方法。详见文章《CEF3开发者系列之JS与C++交互之二》

// Copyright (c) 2013 The Chromium Embedded Framework Authors. All rights
// reserved. Use of this source code is governed by a BSD-style license that
// can be found in the LICENSE file.

#ifndef CEF_TESTS_CEFCLIENT_RENDERER_CLIENT_APP_RENDERER_H_
#define CEF_TESTS_CEFCLIENT_RENDERER_CLIENT_APP_RENDERER_H_
#pragma once

#include <set>

#include "client_app.h"

namespace client {

// Client app implementation for the renderer process.
class ClientAppRenderer : public ClientApp,
                          public CefRenderProcessHandler {
 public:
  // Interface for renderer delegates. All Delegates must be returned via
  // CreateDelegates. Do not perform work in the Delegate
  // constructor. See CefRenderProcessHandler for documentation.
  class Delegate : public virtual CefBase {
   public:
    virtual void OnRenderThreadCreated(CefRefPtr<ClientAppRenderer> app,
                                       CefRefPtr<CefListValue> extra_info) {}

    virtual void OnWebKitInitialized(CefRefPtr<ClientAppRenderer> app) {}

    virtual void OnBrowserCreated(CefRefPtr<ClientAppRenderer> app,
                                  CefRefPtr<CefBrowser> browser) {}

    virtual void OnBrowserDestroyed(CefRefPtr<ClientAppRenderer> app,
                                    CefRefPtr<CefBrowser> browser) {}

    virtual CefRefPtr<CefLoadHandler> GetLoadHandler(
        CefRefPtr<ClientAppRenderer> app) {
      return NULL;
    }

    virtual bool OnBeforeNavigation(CefRefPtr<ClientAppRenderer> app,
                                    CefRefPtr<CefBrowser> browser,
                                    CefRefPtr<CefFrame> frame,
                                    CefRefPtr<CefRequest> request,
                                    cef_navigation_type_t navigation_type,
                                    bool is_redirect) {
      return false;
    }

    virtual void OnContextCreated(CefRefPtr<ClientAppRenderer> app,
                                  CefRefPtr<CefBrowser> browser,
                                  CefRefPtr<CefFrame> frame,
                                  CefRefPtr<CefV8Context> context) {}

    virtual void OnContextReleased(CefRefPtr<ClientAppRenderer> app,
                                   CefRefPtr<CefBrowser> browser,
                                   CefRefPtr<CefFrame> frame,
                                   CefRefPtr<CefV8Context> context) {}

    virtual void OnUncaughtException(CefRefPtr<ClientAppRenderer> app,
                                     CefRefPtr<CefBrowser> browser,
                                     CefRefPtr<CefFrame> frame,
                                     CefRefPtr<CefV8Context> context,
                                     CefRefPtr<CefV8Exception> exception,
                                     CefRefPtr<CefV8StackTrace> stackTrace) {}

    virtual void OnFocusedNodeChanged(CefRefPtr<ClientAppRenderer> app,
                                      CefRefPtr<CefBrowser> browser,
                                      CefRefPtr<CefFrame> frame,
                                      CefRefPtr<CefDOMNode> node) {}

    // Called when a process message is received. Return true if the message was
    // handled and should not be passed on to other handlers. Delegates
    // should check for unique message names to avoid interfering with each
    // other.
    virtual bool OnProcessMessageReceived(
        CefRefPtr<ClientAppRenderer> app,
        CefRefPtr<CefBrowser> browser,
        CefProcessId source_process,
        CefRefPtr<CefProcessMessage> message) {
      return false;
    }
  };

  typedef std::set<CefRefPtr<Delegate> > DelegateSet;

  ClientAppRenderer();

 private:
  // Creates all of the Delegate objects. Implemented by cefclient in
  // client_app_delegates_renderer.cc
  static void CreateDelegates(DelegateSet& delegates);

  // CefApp methods.
  CefRefPtr<CefRenderProcessHandler> GetRenderProcessHandler() OVERRIDE {
    return this;
  }

  // CefRenderProcessHandler methods.
  void OnRenderThreadCreated(CefRefPtr<CefListValue> extra_info) OVERRIDE;
  void OnWebKitInitialized() OVERRIDE;
  void OnBrowserCreated(CefRefPtr<CefBrowser> browser) OVERRIDE;
  void OnBrowserDestroyed(CefRefPtr<CefBrowser> browser) OVERRIDE;
  CefRefPtr<CefLoadHandler> GetLoadHandler() OVERRIDE;
  bool OnBeforeNavigation(CefRefPtr<CefBrowser> browser,
                          CefRefPtr<CefFrame> frame,
                          CefRefPtr<CefRequest> request,
                          NavigationType navigation_type,
                          bool is_redirect) OVERRIDE;
  void OnContextCreated(CefRefPtr<CefBrowser> browser,
                        CefRefPtr<CefFrame> frame,
                        CefRefPtr<CefV8Context> context) OVERRIDE;
  void OnContextReleased(CefRefPtr<CefBrowser> browser,
                         CefRefPtr<CefFrame> frame,
                         CefRefPtr<CefV8Context> context) OVERRIDE;
  void OnUncaughtException(CefRefPtr<CefBrowser> browser,
                           CefRefPtr<CefFrame> frame,
                           CefRefPtr<CefV8Context> context,
                           CefRefPtr<CefV8Exception> exception,
                           CefRefPtr<CefV8StackTrace> stackTrace) OVERRIDE;
  void OnFocusedNodeChanged(CefRefPtr<CefBrowser> browser,
                            CefRefPtr<CefFrame> frame,
                            CefRefPtr<CefDOMNode> node) OVERRIDE;
  bool OnProcessMessageReceived(
      CefRefPtr<CefBrowser> browser,
      CefProcessId source_process,
      CefRefPtr<CefProcessMessage> message) OVERRIDE;

 private:
  // Set of supported Delegates.
  DelegateSet delegates_;

  IMPLEMENT_REFCOUNTING(ClientAppRenderer);
  DISALLOW_COPY_AND_ASSIGN(ClientAppRenderer);
};

}  // namespace client

#endif  // CEF_TESTS_CEFCLIENT_RENDERER_CLIENT_APP_RENDERER_H_

 

至此完结。单进程适用于一些常规需求，比如通过前端的方式来实现界面。实现起来也不复杂，主要是通过本篇文章，再次熟悉下基本的进程模式及其作用。