Best way to execute JS code upon closing?

[robinm2]

The following bit of code used to work reliably in version 86.0.20 (I'm currently trying to upgrade to 126.2.0) :

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// tests/cefclient/browser/root_window_win.cc
bool RootWindowWin::OnClose() {
        CefRefPtr<CefFrame> frame = GetBrowser()->GetMainFrame();
        std::stringstream ss;
        ss << "myFunction();";
        frame->ExecuteJavaScript(ss.str(), frame->GetURL(), 0);
....
}

myFunction is doing some Ajax to record traffic data such as time spent on some page.
In the new CEF version, the function isn't always called.
Is there a known way to have some javascript executed reliably upon closing the browser?

Thanks,

[magreenblatt]

This is generally done from the JavaScript side. See https://developer.chrome.com/docs/web-p ... oad_events for recommendations.

[robinm2]

Cool. Wasn't aware of those alternatives to unload. I'm testing pagehide at the moment, seems to work fine.

[robinm2]

Well, I don't understand, in today's tests the event is not fired when closing the window (it is, however, when I change the URL)
Guess the changes I've made since yesterday broke the apparent reliability? Back to square one anyway.
I'm planning to use libcurl to do the job on the CEF side, I just need the JS app to provide the URL to use.

[robinm2]

If anyone is interested, I ended up not using curl because in certain cases we need to do more than just post to an URL.
The way I managed to reliably call a JS function upon closing is by doing the following modifications:

browser/root_window_win.cc

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// in RootWindowWin::CreateRootWindow
  CHECK(hwnd_);

  browser_window_->GetClientHandler()->SetRootWindowHWND(hwnd_); // sets the custom member root_window_hwnd_ in ClientHandler

...

// in RootWindowWin::RootWndProc
case WM_CLOSE:
        browser = self->GetBrowser();
        if (browser == NULL) {
            return 0;
        }
        if (browser->GetIdentifier() == 1) { // Root window (blank and hidden) : do as usual
            if (self->OnClose()) {
                return 0;  // Cancel the close.
            }
        }
        else { // id > 1 so it's an App window
            if (wParam == 0) { // Origin = user action
                frame = self->GetBrowser()->GetMainFrame();
                frame->ExecuteJavaScript("closeApp();", frame->GetURL(), 0);
                return 0; // Cancel the close
            }
            else if (self->OnClose()) { // Origin = AllowClose
                return 0;  // Cancel the close.
            }
        }
        break;

browser/client_handler.cc

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// in ClientHandler::OnProcessMessageReceived
  else if (message_name == "AllowClose") {
      SendMessage(root_window_hwnd_, WM_CLOSE, 1, NULL);
      return true;
  }

I define the custom JS function "AllowClose"':
shared/renderer/client_app_renderer.cc

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// V8Handler
bool MyV8Handler::Execute(const CefString& name,
    CefRefPtr<CefV8Value> object,
    const CefV8ValueList& arguments,
    CefRefPtr<CefV8Value>& retval,
    CefString& exception) {
    if (name == "AllowClose") {
        CefRefPtr<CefProcessMessage> message = CefProcessMessage::Create("AllowClose");
        CefRefPtr<CefV8Context> context = CefV8Context::GetCurrentContext();
        context->GetFrame()->SendProcessMessage(PID_BROWSER, message);
        retval = CefV8Value::CreateBool(true);
        return true;
    }

    // Function does not exist.
    return false;
}

...

// In ClientAppRenderer::OnContextCreated
  object->SetValue("AllowClose",
      CefV8Value::CreateFunction("AllowClose", handler),
      V8_PROPERTY_ATTRIBUTE_NONE);

Finally, in the JS app:

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let closing = false;
function closeApp() {
  if (!closing) {
    closing = true;
    // do stuff
    post(...).then(AllowClose).catch(AllowClose);
  }
}