Chrome源代码分析之single process 模式分析(十七)

如果选择了单进程模式，那么只需要建立一个renderer线程即可，同时为这个线程搭建ipc功能，虽然同一个进程，renderer与browser之间仍然通过ipc通信，这样多进程和单进程的通信方法统一在一起了。各种IPC消息的映射代码不需要做任何改动。

代码如下：

// Crank up a thread and run the initialization there. With the way that

// messages flow between the browser and renderer, this thread is required

// to prevent a deadlock in single-process mode. Since the primordial

// thread in the renderer process runs the WebKit code and can sometimes

// make blocking calls to the UI thread (i.e. this thread), they need to run

// on separate threads.

in_process_renderer_.reset(new RendererMainThread(channel_id));

base::Thread::Options options;

#if !defined(TOOLKIT_USES_GTK)

// In-process plugins require this to be a UI message loop.

options.message_loop_type = MessageLoop::TYPE_UI;

#else

// We can't have multiple UI loops on GTK, so we don't support

// in-process plugins.

options.message_loop_type = MessageLoop::TYPE_DEFAULT;

#endif

in_process_renderer_->StartWithOptions(options);

OnProcessLaunched(); // Fake a callback that the process is ready.

这里定义个了一个in_process_renderer_代表整个render，RendererMainThread是Thread的子类，RendererMainThread中也有一个RenderProcessImpl类的对象，RenderProcessImpl跟多进程模式下一样有一个main_thread_和io_thread_对象，main_thread_就是前面定义的RendererMainThread线程，后面即会调用n_process_renderer_->StartWithOptions(options);启动这个线程。

RendererMainThread的nit()函数代码如下：

virtual void Init() {

#if defined(OS_WIN)

CoInitialize(NULL);

#endif

render_process_ = new RenderProcessImpl();

render_process_->set_main_thread(new RenderThread(channel_id_));

// It's a little lame to manually set this flag. But the single process

// RendererThread will receive the WM_QUIT. We don't need to assert on

// this thread, so just force the flag manually.

// If we want to avoid this, we could create the InProcRendererThread

// directly with _beginthreadex() rather than using the Thread class.

base::Thread::SetThreadWasQuitProperly(true);

}

virtual void CleanUp() {

delete render_process_;

#if defined(OS_WIN)

CoUninitialize();

#endif

}

这里面会新建RenderProcessImpl的对象，如同多进程模式一样，ipc对象和io线程随后会在RenderThread和RenderProcessImpl的构造函数中被创建和初始化。