HOWTO: post messages between threads with Boost::asio?

Question

Sorry for my english

I've searched around, but did not get an answer to this question: I have a windows application project, using boost thread libraries. I want to post messages(or, invoke callbacks) from a worker's thread to the main UI thread. I studied the samples in boost::asio, all of them used in a blocked main thread, but my UI thread is working asynchronous.

Would you please help me? thanks a lot!

Answer 1

Since the UI thread has its own message loop, you can't call in its context the blocking io_service::run() function. What you can do is to interleave a polling UI-related method with io_service::poll_one():

  // WARINING: untested code
  MSG msg;
  while (PeekMessage(&msg, 0, 0, 0, PM_REMOVE))
  {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
    if (io_service_.stopped())
      io_service_.reset();
    error_code ec;
    io_service_.poll_one(ec);
  }

Now, when you post functors to io_service_, you actually post them to the main GUI thread.

(Certainly, if you use some GUI framework, you should use the appropriate framework method instead of PeekMessage.)

Answer 2

The UI thread is it a webkit similar kind of UI or plain windows forms, because if you are using webkit then u can handle it in a different way. OR Try using Delegates. OR finally if nothing works out, you can run a while loop checking an vector for any new input and add to the vector from the thread callback function.

I prefer if you could use delegate. (pointer function)

Here is a sample code for pointer function:

define a function like this:

typedef boost::function<void(std::string)> fnLog;

or if u want to go specifically for windows then

typedef void (__stdcall *fnLog)(char* val);

fnLog is the function with std::string parameter. then bind your function which is in UI thread to the pointer function

fnLog myPointerFunc = boost::bind( &UI::f1, _1);

then pass

myPointerFunc

as callback.

for more reference check on http://www.radmangames.com/programming/how-to-use-boost-function