cef源码分析之cefsimple
下面是cefsimple的入口代码，主要分成两个部分
// Entry point function for all processes.
int APIENTRY wWinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPTSTR lpCmdLine,
int nCmdShow) {
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
// Enable High-DPI support on Windows 7 or newer.
CefEnableHighDPISupport();
void* sandbox_info = NULL;
#if defined(CEF_USE_SANDBOX)
// Manage the life span of the sandbox information object. This is necessary
// for sandbox support on Windows. See cef_sandbox_win.h for complete details.
CefScopedSandboxInfo scoped_sandbox;
sandbox_info = scoped_sandbox.sandbox_info();
#endif
// Provide CEF with command-line arguments.
CefMainArgs main_args(hInstance);
// CEF applications have multiple sub-processes (render, plugin, GPU, etc)
// that share the same executable. This function checks the command-line and,
// if this is a sub-process, executes the appropriate logic.
int exit_code = CefExecuteProcess(main_args, NULL, sandbox_info);
if (exit_code >= 0) {
// The sub-process has completed so return here.
return exit_code;
}
// Specify CEF global settings here.
CefSettings settings;
#if !defined(CEF_USE_SANDBOX)
settings.no_sandbox = true;
#endif
// SimpleApp implements application-level callbacks for the browser process.
// It will create the first browser instance in OnContextInitialized() after
// CEF has initialized.
CefRefPtr<SimpleApp> app(new SimpleApp);
// Initialize CEF.
CefInitialize(main_args, settings, app.get(), sandbox_info);
// Run the CEF message loop. This will block until CefQuitMessageLoop() is
// called.
CefRunMessageLoop();
// Shut down CEF.
CefShutdown();
return 0;
}
进程判断
首先是初始化进程的代码，cef的进程结构和chromium类似，都是多进程共用代码。所以cef提供了一些函数来检测主进程（即browser进程）的流程和子进程的流程，以分别执行适合当前执行进程的逻辑。这段代码如下所示。
// CEF applications have multiple sub-processes (render, plugin, GPU, etc)
// that share the same executable. This function checks the command-line and,
// if this is a sub-process, executes the appropriate logic.
int exit_code = CefExecuteProcess(main_args, NULL, sandbox_info);
if (exit_code >= 0) {
// The sub-process has completed so return here.
return exit_code;
}
其中main_args用于获取当前进程的命令行参数，因为在chromium中，进程的区分就是靠命令行参数中的--type，如果是browser进程，则没有--type参数，其他进程该参数的值为renderer,gpu等
int CefExecuteProcess(const CefMainArgs& args,
CefRefPtr<CefApp> application,
void* windows_sandbox_info) {
#if defined(OS_WIN)
#if defined(ARCH_CPU_X86_64)
DisableFMA3();
#endif
InitInstallDetails();
InitCrashReporter();
#endif
base::CommandLine command_line(base::CommandLine::NO_PROGRAM);
#if defined(OS_WIN)
command_line.ParseFromString(::GetCommandLineW());
#else
command_line.InitFromArgv(args.argc, args.argv);
#endif
// Wait for the debugger as early in process initialization as possible.
if (command_line.HasSwitch(switches::kWaitForDebugger))
base::debug::WaitForDebugger(60, true);
// If no process type is specified then it represents the browser process and
// we do nothing.
std::string process_type =
command_line.GetSwitchValueASCII(switches::kProcessType);
if (process_type.empty())
return -1;
#if defined(OS_MACOSX) || defined(OS_WIN)
if (process_type == crash_reporter::switches::kCrashpadHandler)
return RunAsCrashpadHandler(command_line);
#endif
CefMainDelegate main_delegate(application);
// Execute the secondary process.
#if defined(OS_WIN)
sandbox::SandboxInterfaceInfo sandbox_info = {0};
if (windows_sandbox_info == NULL) {
content::InitializeSandboxInfo(&sandbox_info);
windows_sandbox_info = &sandbox_info;
}
content::ContentMainParams params(&main_delegate);
params.instance = args.instance;
params.sandbox_info =
static_cast<sandbox::SandboxInterfaceInfo*>(windows_sandbox_info);
return content::ContentMain(params);
#else
content::ContentMainParams params(&main_delegate);
params.argc = args.argc;
params.argv = const_cast<const char**>(args.argv);
return content::ContentMain(params);
#endif
}
只有当非browser进程时才会执行ContentMain函数，这也符合chromium的逻辑。ContentMain函数是其他子进程的入口点。
而browser进程则会返回执行CefInitialize和CefRunMessageLoop进入browser进程的主循环。当进程需要退出时，CefRunMessageLoop主循环退出，执行CefShutdown进程结束。
cef的browser进程启动
第二个部分就是browser进程的主流程，下面是拆分出来的代码。
// Initialize CEF.
CefInitialize(main_args, settings, app.get(), sandbox_info);
// Run the CEF message loop. This will block until CefQuitMessageLoop() is
// called.
CefRunMessageLoop();
// Shut down CEF.
CefShutdown();
首先看CefInitialize初始化函数，其中app.get()即CefApp对象指针的参数尤为重要，在文件libcef/browser/context.cc中，提供了不少类似CefInitialize的cef控制函数，初始化，关闭，开启和退出消息循环等
bool CefInitialize(const CefMainArgs& args,
const CefSettings& settings,
CefRefPtr<CefApp> application,
void* windows_sandbox_info) {
#if defined(OS_WIN)
#if defined(ARCH_CPU_X86_64)
DisableFMA3();
#endif
InitInstallDetails();
InitCrashReporter();
#endif
// Return true if the global context already exists.
if (g_context)
return true;
if (settings.size != sizeof(cef_settings_t)) {
NOTREACHED() << "invalid CefSettings structure size";
return false;
}
g_browser_process = new ChromeBrowserProcessStub();
// Create the new global context object.
g_context = new CefContext();
// Initialize the global context.
return g_context->Initialize(args, settings, application,
windows_sandbox_info);
}
为的是创建一个全局的CefContext对象，只有当CefContext对象被创建完成后，才能进行CreateBrowser操作，在下面的代码中
return g_context->Initialize(args, settings, application,
windows_sandbox_info);
Initialize的主要作用是根据content api开始做浏览器进程启动准备。因为content api要涉及chromium代码，这里就不继续往下追溯，主要看cef的流程
bool CefContext::Initialize(const CefMainArgs& args,
const CefSettings& settings,
CefRefPtr<CefApp> application,
void* windows_sandbox_info) {
...
main_delegate_.reset(new CefMainDelegate(application));
...
if (CEF_CURRENTLY_ON_UIT()) {
OnContextInitialized();
} else {
// Continue initialization on the UI thread.
CEF_POST_TASK(CEF_UIT, base::Bind(&CefContext::OnContextInitialized,
base::Unretained(this)));
}
...
CefApp的引用会一直传递到这里，当初始化的流程结束的时候（OnContextInitialized），就到了CefApp发挥作用的时候了。
其中main_delegate_作为一个代理，主要代理总体管理的相关功能，包括资源初始化，浏览器关闭等。那么CefApp对它有什么用呢？主要是为了创建一个全局的CefContentClient对象。
CefMainDelegate::CefMainDelegate(CefRefPtr<CefApp> application)
: content_client_(application) {
然后当CefContext初始化完成后，就会从这个全局的CefContentClient对象中获取CefApp的引用。而获得引用之后是为了获得handler，以完成对应的回调。
void CefContext::OnContextInitialized() {
CEF_REQUIRE_UIT();
static_cast<ChromeBrowserProcessStub*>(g_browser_process)
->OnContextInitialized();
#if BUILDFLAG(ENABLE_WIDEVINE) && BUILDFLAG(ENABLE_LIBRARY_CDMS)
CefWidevineLoader::GetInstance()->OnContextInitialized();
#endif
// Notify the handler.
CefRefPtr<CefApp> app = CefContentClient::Get()->application();
if (app.get()) {
CefRefPtr<CefBrowserProcessHandler> handler =
app->GetBrowserProcessHandler();
if (handler.get())
handler->OnContextInitialized();
}
}
此处主要获取的是browser process handler，这个handler的主要目的是监控并触发browser进程生命周期内各个关键时机的回调。
如果多少用过cef，会知道browser进程中很重要的一个函数就是CreateBrowser，cefsimple这个demo中，使用在了OnContextInitialized函数中，这说明，当cef上下文初始化完成之后就可以创建浏览功能了。
void SimpleApp::OnContextInitialized() {
CEF_REQUIRE_UI_THREAD();
CefRefPtr<CefCommandLine> command_line =
CefCommandLine::GetGlobalCommandLine();
#if defined(OS_WIN) || defined(OS_LINUX)
// Create the browser using the Views framework if "--use-views" is specified
// via the command-line. Otherwise, create the browser using the native
// platform framework. The Views framework is currently only supported on
// Windows and Linux.
const bool use_views = command_line->HasSwitch("use-views");
#else
const bool use_views = false;
#endif
// SimpleHandler implements browser-level callbacks.
CefRefPtr<SimpleHandler> handler(new SimpleHandler(use_views));
// Specify CEF browser settings here.
CefBrowserSettings browser_settings;
std::string url;
// Check if a "--url=" value was provided via the command-line. If so, use
// that instead of the default URL.
url = command_line->GetSwitchValue("url");
if (url.empty())
url = "http://www.google.com";
if (use_views) {
// Create the BrowserView.
CefRefPtr<CefBrowserView> browser_view = CefBrowserView::CreateBrowserView(
handler, url, browser_settings, NULL, NULL, NULL);
// Create the Window. It will show itself after creation.
CefWindow::CreateTopLevelWindow(new SimpleWindowDelegate(browser_view));
} else {
// Information used when creating the native window.
CefWindowInfo window_info;
#if defined(OS_WIN)
// On Windows we need to specify certain flags that will be passed to
// CreateWindowEx().
window_info.SetAsPopup(NULL, "cefsimple");
#endif
// Create the first browser window.
CefBrowserHost::CreateBrowser(window_info, handler, url, browser_settings,
NULL, NULL);
}
}
而对应的ShutdownBrowser则是在CefContext::Shutdown()中被调用。并不需要开发者过多操作。
