Scheme Handler freeze the UI

[abizeau]

Hello,

I have an image processing call (about 5 to 10 second) inside a ProcessRequest() and my XHR is async, but the UI still freeze.

Is there any thing to do such as using callback function or use threading ?

Regards,
Alex

[magreenblatt]

Do not perform blocking work on the IO thread (inside ProcessRequest). Do the work on a different thread and use the async callback to continue when done.

[abizeau]

When you means another thread, a std::thread or Renderer thread ?

Do you have any example or topics to link ? I search a bit and I found nothing about it.

[magreenblatt]

You can create the new thread however you like. CEF also provides a CefThread class.

[abizeau]

Just to inform anyone who search for something like this, here an example:

Code: Select all

bool ProcessRequest(CefRefPtr<CefRequest> request, CefRefPtr<CefCallback> callback)
{
    if ( strstr(url.c_str(), "myaction") != NULL )
    {
        std::async(&RunLongProcess, this, request->GetPostData(), callback);
        return true; // Handled request;
    }

    // Dont put the Callback->Continue() here, reserve it for your thread.
    return false;
}


void RunLongProcess(CefRefPtr<CefPostData> postData, CefRefPtr<CefCallback> callback)
{
    // Check if postData has been provided.
    if ( postData == NULL )   
        Callback->Cancel(); // Cancel the request.

   // processing ...

    // Similar to other ProcessRequest set the m_data and your m_mime_type (if you have one).

    // Then send to the factory, that the request is finished to process
    // and it can now call the GetResponseHeaders and ReadResponse.
    Callback->Continue();
}



[abizeau]

I discover that std::async(); have a different behavior on Mac OS. To be able to return true, you might want to use std::thread().detach(); instead. Else the thread is block after the return, to wait for the dtor to finish, which wait for the async thread.

So the solution in the

Code: Select all

bool ProcessRequest(CefRefPtr<CefRequest> request, CefRefPtr<CefCallback> callback)
{
    if ( strstr(url.c_str(), "myaction") != NULL )
    {
        std::thread(&RunLongProcess, this, request->GetPostData(), callback)­.detach();
        return true; // Handled request;
    }

    // Dont put the Callback->Continue() here, reserve it for your thread.
    return false;
}