下面是cefsimple的入口代碼，主要分成兩個部分
// 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;
}
行程判斷
首先是初始化行程的代碼，cef的行程結構和chromium類似，都是多行程共用代碼，所以cef提供了一些函式來檢測主行程（即browser行程）的流程和子行程的流程，以分別執行適合當前執行行程的邏輯，這段代碼如下所示，
// 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用于獲取當前行程的命令列引數，因為在chromium中，行程的區分就是靠命令列引數中的--type，如果是browser行程，則沒有--type引數，其他行程該引數的值為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
}
只有當非browser行程時才會執行ContentMain函式，這也符合chromium的邏輯，ContentMain函式是其他子行程的入口點，
而browser行程則會回傳執行CefInitialize和CefRunMessageLoop進入browser行程的主回圈，當行程需要退出時，CefRunMessageLoop主回圈退出，執行CefShutdown行程結束，
cef的browser行程啟動
第二個部分就是browser行程的主流程，下面是拆分出來的代碼，
// 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初始化函式，其中app.get()即CefApp物件指標的引數尤為重要，在檔案libcef/browser/context.cc中，提供了不少類似CefInitialize的cef控制函式，初始化，關閉，開啟和退出訊息回圈等
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);
}
為的是創建一個全域的CefContext物件，只有當CefContext物件被創建完成后，才能進行CreateBrowser操作，在下面的代碼中
return g_context->Initialize(args, settings, application,
windows_sandbox_info);
Initialize的主要作用是根據content api開始做瀏覽器行程啟動準備，因為content api要涉及chromium代碼，這里就不繼續往下追溯，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的參考會一直傳遞到這里，當初始化的流程結束的時候（OnContextInitialized），就到了CefApp發揮作用的時候了，
其中main_delegate_作為一個代理，主要代理總體管理的相關功能，包括資源初始化，瀏覽器關閉等，那么CefApp對它有什么用呢？主要是為了創建一個全域的CefContentClient物件，
CefMainDelegate::CefMainDelegate(CefRefPtr<CefApp> application)
: content_client_(application) {
然后當CefContext初始化完成后，就會從這個全域的CefContentClient物件中獲取CefApp的參考，而獲得參考之后是為了獲得handler，以完成對應的回呼，
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();
}
}
此處主要獲取的是browser process handler，這個handler的主要目的是監控并觸發browser行程生命周期內各個關鍵時機的回呼，
如果多少用過cef，會知道browser行程中很重要的一個函式就是CreateBrowser，cefsimple這個demo中，使用在了OnContextInitialized函式中，這說明，當cef背景關系初始化完成之后就可以創建瀏覽功能了，
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);
}
}
而對應的ShutdownBrowser則是在CefContext::Shutdown()中被呼叫，并不需要開發者過多操作，
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標籤：其他