应用退出时CEF崩溃(QT5+CEF3.2526)

Question

这是一个非常简单的QT+CEF windows应用程序，请参阅https://github.com/GreatTux/CefMinGWQt

当我关闭主窗口时，CEF触发断点:我想我在这里失败了：

void CefBrowserMainParts::PostMainMessageLoopRun() {
....
#ifndef NDEBUG
// No CefBrowserContext instances should exist at this point.
DCHECK_EQ(0, CefBrowserContext::DebugObjCt);
#endif
}

我不知道释放浏览器资源的正确方法是什么，我在web上看了很多例子，几乎所有的例子都在我的Windows 7+vs2010环境中遇到了这个问题

我也试过了，但不起作用

void ClientHandler::OnBeforeClose(CefRefPtr<CefBrowser> browser) {
  if(m_browser.get())
    m_browser = NULL;

====跟踪===

libcef.dll!base::debug::BreakDebugger()  Line 21    C++
libcef.dll!logging::LogMessage::~LogMessage()  Line 604 C++
libcef.dll!CefBrowserMainParts::PostMainMessageLoopRun()  Line 189  C++
libcef.dll!content::BrowserMainLoop::ShutdownThreadsAndCleanUp()  Line 946 + 0x27 bytes C++
libcef.dll!content::BrowserMainRunnerImpl::Shutdown()  Line 293 C++
libcef.dll!CefMainDelegate::ShutdownBrowser()  Line 659 + 0x1b bytes    C++
libcef.dll!CefContext::FinalizeShutdown()  Line 462 C++
libcef.dll!CefContext::Shutdown()  Line 345 C++
libcef.dll!CefShutdown()  Line 171  C++
libcef.dll!cef_shutdown()  Line 192 C++
qtloop.exe!CefShutdown()  Line 180 + 0x8 bytes  C++
qtloop.exe!main(int argc=1, char * * argv=0x00375b90)  Line 35  C++
qtloop.exe!WinMain(HINSTANCE__ * __formal=0x00fe0000, HINSTANCE__ *    __formal=0x00fe0000, HINSTANCE__ * __formal=0x00fe0000, HINSTANCE__ * __formal=0x00fe0000)  Line 113 + 0xd bytes C++
qtloop.exe!__tmainCRTStartup()  Line 547 + 0x2c bytes   C
qtloop.exe!WinMainCRTStartup()  Line 371    C

Answer 1

当您关闭主窗口时，Qt不会立即销毁它，因此cef浏览器不会发布。此时返回app.exec()，运行CefShowDown()并触发调试检查。

我也遇到过同样的问题。这是因为当你关闭Cef时，也有一些浏览器是不可用的

DCHECK_EQ(0，CefBrowserContext::DebugObjCt)；

我阅读了这篇文章并阅读了cef close process的源代码。

https://github.com/fanfeilong/cefutil/blob/master/doc/CEF_Close.md

我解决了这个问题，关键是，当你打电话给

GetHost()->CloseBrowser(false)

在cef上嵌入父窗口的closeEvent并忽略第一个closeEvent

然后，如果允许用户关闭，cef将再次发送close到父根窗口。

void CefBrowserHostImpl::PlatformCloseWindow() {
  if (window_info_.window != NULL) {
    HWND frameWnd = GetAncestor(window_info_.window, GA_ROOT);
    PostMessage(frameWnd, WM_CLOSE, 0, 0);
  }
}

当你收到第二个关闭，你需要确保关闭窗口，并立即销毁cef嵌入的窗口。Cef需要WM_DESTROY事件来释放资源并调用OnBeforeClose。

Answer 2

您需要钩子窗口关闭操作，并确保cef浏览器先关闭。

标准流程是(摘自cef注释，稍作修改)：

//
// 1.  User clicks the window close button which sends a close notification to
//     the application's top-level window.
// 2.  Application's top-level window receives the close notification and:
//     A. Calls CefBrowserHost::CloseBrowser(false).
//     B. Cancels the window close.
// 3.  JavaScript 'onbeforeunload' handler executes and shows the close
//     confirmation dialog (which can be overridden via
//     CefJSDialogHandler::OnBeforeUnloadDialog()).
// 4.  User approves the close.
// 5.  JavaScript 'onunload' handler executes.
// 6.  Application's DoClose() handler is called. Application will:
//     A. Set a flag to indicate that the next close attempt will be allowed.
//     B. Return false.
// 7.  Sends an close notification to the application's top-level window.
// 8.  Application's top-level window receives the close notification and
//     allows the window to close based on the flag from #6B.
// 9.  Application's top-level window is destroyed.
// 10. Application's OnBeforeClose() handler is called and the browser object
//     is destroyed.
// 11. Application exits by calling CefQuitMessageLoop() if no other browsers
//     exist.
///

我写了一个名为QCefWidget的项目，它基于QT + CEF OSR。它有一个完美的退出逻辑。你可以参考它