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‎doc/CEF_Close.md

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我来说windows下CEF3.2171的关闭流程，里面会引用一部分官方库的文档和个人的伪代码，为了辅助理解——
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以下是截取自cef_life_span_handler.h的头文件文档，所以一部分文档他还是写在头文件里的，根据他的流程，能很快的去梳理相关逻辑
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// The CefLifeSpanHandler::OnBeforeClose() method will be called immediately
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// before the browser object is destroyed. The application should only exit
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// after OnBeforeClose() has been called for all existing browsers.
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//
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// If the browser represents a modal window and a custom modal loop
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// implementation was provided in CefLifeSpanHandler::RunModal() this callback
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// should be used to restore the opener window to a usable state.
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//
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// By way of example consider what should happen during window close when the
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// browser is parented to an application-provided top-level OS window.
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// 1. User clicks the window close button which sends an OS close
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// notification (e.g. WM_CLOSE on Windows, performClose: on OS-X and
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// "delete_event" on Linux).
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// 2. Application's top-level window receives the close notification and:
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// A. Calls CefBrowserHost::CloseBrowser(false).
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// B. Cancels the window close.
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// 3. JavaScript 'onbeforeunload' handler executes and shows the close
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// confirmation dialog (which can be overridden via
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// CefJSDialogHandler::OnBeforeUnloadDialog()).
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// 4. User approves the close.
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// 5. JavaScript 'onunload' handler executes.
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// 6. Application's DoClose() handler is called. Application will:
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// A. Set a flag to indicate that the next close attempt will be allowed.
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// B. Return false.
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// 7. CEF sends an OS close notification.
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// 8. Application's top-level window receives the OS close notification and
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// allows the window to close based on the flag from #6B.
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// 9. Browser OS window is destroyed.
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// 10. Application's CefLifeSpanHandler::OnBeforeClose() handler is called and
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// the browser object is destroyed.
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// 11. Application exits by calling CefQuitMessageLoop() if no other browsers
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// exist.
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pre1. 如果你要管理CefBrowser的生命周期，意味者你必须实现相关 CefLifeSpanHandler接口，在OnAfterCreated里管理和获取CefBrowser的每一个browser，在DoClose和OnBeforeClose里管理关闭
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pre2. 这里要注意整个流程对应开发者来说不是线性代码，都是基于消息、事件投递、接口切面的一种编程习惯，大家要对异步接口的开发有心理准备，你实现的一个接口都是等待框架或者别人调用。
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1. 用户发起了一个系统级别的关闭操作，比如CLOSE，window下会被WM_CLOSE和相关封装触发
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2. 系统的顶层窗口消息处理会获取到CLOSE消息
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  A. 调用 CefBrowserHost::CloseBrowser(false), 通知HOST开始关闭流程，参数force_close=false，我们不需要交互式关闭。
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  B. 取消系统级关闭，比如以下代码我"return 0; "拒接了系统窗口的关闭流程，进入了个人和CEF的流程
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```c++
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case WM_CLOSE:
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if (client && !client->IsClosing()) {
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CefRefPtr<CefBrowser> browser = client->GetBrowser();
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if (browser.get()) {
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// Notify the browser window that we would like to close it. This
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// will result in a call to ClientHandler::DoClose() if the
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// JavaScript 'onbeforeunload' event handler allows it.
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browser->GetHost()->CloseBrowser(false);
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// Cancel the close.
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return 0;
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}
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}
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// Allow the close.
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break;
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```
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这是单browser关闭
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```C++
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browser->GetHost()->CloseBrowser(false);
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```
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同样可以替换成多browser关闭
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```C++
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void ClientHandler::CloseAllBrowsers(bool force_close) {
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if (!CefCurrentlyOn(TID_UI)) {
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// Execute on the UI thread.
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CefPostTask(TID_UI,
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base::Bind(&ClientHandler::CloseAllBrowsers, this, force_close));
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return;
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}
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if (!popup_browsers_.empty()) {
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// Request that any popup browsers close.
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BrowserList::const_iterator it = popup_browsers_.begin();
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for (; it != popup_browsers_.end(); ++it)
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(*it)->GetHost()->CloseBrowser(force_close);
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}
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if (browser_.get()) {
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// Request that the main browser close.
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browser_->GetHost()->CloseBrowser(force_close);
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}
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}
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```
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intermittent.
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最终会触发一个或多个CloseBrowser => CefBrowserHostImpl::CloseBrowser => CefBrowserHostImpl::CloseContents
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``` C++
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void CefBrowserHostImpl::CloseBrowser(bool force_close) {
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if (CEF_CURRENTLY_ON_UIT()) {
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// Exit early if a close attempt is already pending and this method is
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// called again from somewhere other than WindowDestroyed().
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if (destruction_state_ >= DESTRUCTION_STATE_PENDING &&
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(IsWindowless() || !window_destroyed_)) {
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if (force_close && destruction_state_ == DESTRUCTION_STATE_PENDING) {
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// Upgrade the destruction state.
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destruction_state_ = DESTRUCTION_STATE_ACCEPTED;
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}
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return;
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}
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if (destruction_state_ < DESTRUCTION_STATE_ACCEPTED) {
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destruction_state_ = (force_close ? DESTRUCTION_STATE_ACCEPTED :
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DESTRUCTION_STATE_PENDING);
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}
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content::WebContents* contents = web_contents();
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if (contents && contents->NeedToFireBeforeUnload()) {
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// Will result in a call to BeforeUnloadFired() and, if the close isn't
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// canceled, CloseContents().
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contents->DispatchBeforeUnload(false);
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} else {
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CloseContents(contents);
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}
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} else {
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CEF_POST_TASK(CEF_UIT,
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base::Bind(&CefBrowserHostImpl::CloseBrowser, this, force_close));
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}
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}
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```
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我们跳过其他细节（ 我也没关注:) ），和相关CEF_POST_TASK把函数投递到UI线程上去处理的线程类型,最后会进入 CloseContents
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```C++
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void CefBrowserHostImpl::CloseContents(content::WebContents* source) {
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if (destruction_state_ == DESTRUCTION_STATE_COMPLETED)
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return;
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bool close_browser = true;
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// If this method is called in response to something other than
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// WindowDestroyed() ask the user if the browser should close.
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if (client_.get() && (IsWindowless() || !window_destroyed_)) {
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CefRefPtr<CefLifeSpanHandler> handler =
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client_->GetLifeSpanHandler();
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if (handler.get()) {
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close_browser = !handler->DoClose(this); // CefLifeSpanHandler::DoClose
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}
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}
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if (close_browser) {
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if (destruction_state_ != DESTRUCTION_STATE_ACCEPTED)
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destruction_state_ = DESTRUCTION_STATE_ACCEPTED;
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if (!IsWindowless() && !window_destroyed_) {
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// A window exists so try to close it using the platform method. Will
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// result in a call to WindowDestroyed() if/when the window is destroyed
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// via the platform window destruction mechanism.
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PlatformCloseWindow();
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} else {
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// Keep a reference to the browser while it's in the process of being
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// destroyed.
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CefRefPtr<CefBrowserHostImpl> browser(this);
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// No window exists. Destroy the browser immediately.
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DestroyBrowser(); // CefLifeSpanHandler::OnBeforeClose
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if (!IsWindowless()) {
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// Release the reference added in PlatformCreateWindow().
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Release();
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}
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}
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} else if (destruction_state_ != DESTRUCTION_STATE_NONE) {
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destruction_state_ = DESTRUCTION_STATE_NONE;
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}
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}
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```
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在CloseContents里发现了我们的DoClose接口，其实这个函数里还有我们要处理的OnBeforeClose接口，DestroyBrowser包含了他
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```C++
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void CefBrowserHostImpl::DestroyBrowser() {
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CEF_REQUIRE_UIT();
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destruction_state_ = DESTRUCTION_STATE_COMPLETED;
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if (client_.get()) {
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CefRefPtr<CefLifeSpanHandler> handler = client_->GetLifeSpanHandler();
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if (handler.get()) {
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// Notify the handler that the window is about to be closed.
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handler->OnBeforeClose(this); //`CefLifeSpanHandler::OnBeforeClose
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}
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}
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// 省略
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}
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```
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到这里我们要有这样的调用栈初步概念（之后会修改..)
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```C++
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=> 表示同步调用 ->异步调用
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[os]window close =>
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[个人]browser(s) close =>
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[cef]CefBrowserHostImpl::CloseBrowser =>
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[cef]CefBrowserHostImpl::CloseContents =>
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[实现cef接口]CefLifeSpanHandler::DoClose =>
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[cef]CefLifeSpanHandler::DestroyBrowser =>
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[实现cef接口]CefLifeSpanHandler::OnBeforeClose =>
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[os]阻止window close
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```
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3-5. js和交互级的操作，略，其中有一点js onunload让你有机会在js层面去通知关闭，比如通知后台的native 线程去做自我清理动作，特别是cefQuery持久化以后的和JS交互的native线程
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6.DoClose接口被调用
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&ensp;&ensp;A. 允许设置一些状态表示browser正在关闭
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&ensp;&ensp;B. "return false;" 我们不需要紧急关闭（好像是预留接口，或者其他平台用)
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7.cef 发送一个系统级别的关闭动作发现之前的调用栈已经需要修改了，因为这里异步操作)
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CloseContents => PlatformCloseWindow => CefBrowserHostImpl::PlatformCloseWindow =>PostMessage WM_CLOSE
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```C++
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void CefBrowserHostImpl::PlatformCloseWindow() {
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if (window_info_.window != NULL) {
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HWND frameWnd = GetAncestor(window_info_.window, GA_ROOT);
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PostMessage(frameWnd, WM_CLOSE, 0, 0);
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}
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}
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```
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PS: host公共代码在这个文件browser_host_impl.cc里，平台特殊接口在browser_host_impl_xxx.cc里
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PlatformCloseWindow在browser_host_impl_win.cc里
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允许关闭"if (client && !client->IsClosing()) " 之前我代码里IsClosing已经允许（
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```C++
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case WM_CLOSE:
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if (client && !client->IsClosing()) {
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// 这次不会进入IF分支
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```
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8.系统窗口已销毁
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```C++
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LRESULT CALLBACK CefBrowserHostImpl::WndProc(HWND hwnd, UINT message,
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WPARAM wParam, LPARAM lParam) {
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// 略
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case WM_DESTROY:
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if (browser) {
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// Clear the user data pointer.
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gfx::SetWindowUserData(hwnd, NULL);
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// Force the browser to be destroyed and release the reference added in
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// PlatformCreateWindow().
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browser->WindowDestroyed();
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}
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return 0;
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// 略
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}
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```
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cef竟然在等系统群发销毁消息然后处理的代码，看到这里才发现CefBrowserHostImpl这个类是CefBrowser和系统整合的桥梁，不同平台对 CefBrowserHostImpl 的实现也不一样
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9.框架发起销毁操作
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10. 调用OnBeforeClose
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WM_DESTROY => CefBrowserHostImpl::WindowDestroyed => ClientHandler::OnBeforeClose
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```C++
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void ClientHandler::OnBeforeClose(CefRefPtr<CefBrowser> browser) {
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CEF_REQUIRE_UI_THREAD();
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message_router_->OnBeforeClose(browser);
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if (GetBrowserId() == browser->GetIdentifier()) {
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{
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base::AutoLock lock_scope(lock_);
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// Free the browser pointer so that the browser can be destroyed
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browser_ = NULL;
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}
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if (osr_handler_.get()) {
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osr_handler_->OnBeforeClose(browser);
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osr_handler_ = NULL;
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}
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} else if (browser->IsPopup()) {
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// Remove from the browser popup list.
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BrowserList::iterator bit = popup_browsers_.begin();
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for (; bit != popup_browsers_.end(); ++bit) {
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if ((*bit)->IsSame(browser)) {
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popup_browsers_.erase(bit);
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break;
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}
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}
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}
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if (--browser_count_ == 0) {
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// All browser windows have closed.
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// Remove and delete message router handlers.
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MessageHandlerSet::const_iterator it = message_handler_set_.begin();
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for (; it != message_handler_set_.end(); ++it) {
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message_router_->RemoveHandler(*(it));
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delete *(it);
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}
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message_handler_set_.clear();
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message_router_ = NULL;
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// Quit the application message loop.
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//AppQuitMessageLoop();
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XCefAppManage::Instance()->QuitMessageLoop();
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}
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}
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```
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我判断到 "--browser_count_ == 0" , 开始发起真实关闭。
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11. 发起的真实关闭逻辑
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个人在OnBeforeClose里销毁所有browser和相关操作cefquery组件销毁以后，发起了总的关闭流程（关闭是异步的）
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```C++
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void XCefAppManage::QuitMessageLoop() {
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if (GetCefSettings().multi_threaded_message_loop)
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{
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// Running in multi-threaded message loop mode. Need to execute
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// PostQuitMessage on the main application thread.
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if (NULL == message_wnd__)
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{
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message_wnd__ = ::FindWindow(XWinUtil::GetMessageWindowClassName(XWinUtil::GetParentProcessID()), NULL);
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}
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DCHECK(message_wnd__);
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PostMessage(message_wnd__, WM_COMMAND, ID_QUIT, 0);
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}
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else {
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CefQuitMessageLoop();
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}
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}
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```
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如果CefRunMessageLoop创建的消息循环对应CefQuitMessageLoop去终结，其他方式的处理就千奇百怪了，我根据cefclient的例子用一个隐藏窗口来结束系统的消息循环
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```C++
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PostMessage(message_wnd__, WM_COMMAND, ID_QUIT, 0);
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```
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处理非常简单，调用了原生API PostQuitMessage退出循环
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```C++
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case ID_QUIT:
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PostQuitMessage(0);
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return 0;
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```
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PS: 如果需要把CEF混入其他框架的话，不同框架的处理都需要适配，切记。
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12. CefShutDown() 销毁Cef资源，如果有资源没关闭，比如browser的计数不为0，debug下会check assert。
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最后我再来修改一下之前的调用栈
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```C++
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=> 表示同步调用 ->异步调用
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[os]on window close WM_CLOSE =>
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[个人]browser(s) close =>
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[cef]CefBrowserHostImpl::CloseBrowser =>
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[cef]CefBrowserHostImpl::CloseContents =>
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[实现cef接口]CefLifeSpanHandler::DoClose =>
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[cef]CefBrowserHostImpl::PlatformCloseWindow =>
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[os] post window close -> WM_CLOSE
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[os]阻止window close
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post被接收
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[os] 第二次on window close WM_CLOSE =>
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[个人] 允许 window close ->WM_DESTROY
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[os] 系统群发WM_DESTROY
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[cef] CefBrowserHostImpl::WndProc =>
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[cef & os] 每个browser proc内的 WM_CLOSE 处理
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[cef]CefLifeSpanHandler::DestroyBrowser =>
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[实现cef接口]CefLifeSpanHandler::OnBeforeClose =>
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发起总关闭(个人使用XCefAppManage::QuitMessageLoop)->
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退出消息循环
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CefShutDown
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```
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这就一些对CEF CLOSE的个人理解的心得

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