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    <p>If I understand your question correctly, you have code written for Boost.Asio . You would like to use that code inside a GUI application.</p> <p>What is not clear in your question is if you want to wrap the Qt/Gtk network layers through asynio for your code to work, if you are just looking for a solution for having both a gui event loop and asynio together.</p> <p>I will assume the second case.</p> <p>Both Qt and Gtk have methods to integrate foreign events in their event loop. See for example <a href="http://developer.kde.org/documentation/tutorials/qtgtk/main.html" rel="nofollow noreferrer">qtgtk</a> where the Qt event loop is plugged into Gtk.</p> <p>In the specific case of Qt, if you want to generate events for Qt, you can use the following class: <a href="http://qt-project.org/doc/qt-5/qabstracteventdispatcher.html" rel="nofollow noreferrer">QAbstractEventDispatcher</a>.</p> <p>After a quick look at boost asio, I think you need to do the following:</p> <ul> <li>have a recurring QTimer with duration zero that calls io_service::run() all the time. That way, boost::asio will call your completion handler as soon as your asynchronous operation is completed.</li> <li>in your completion handler, two options: <ul> <li>if your completion operation is a long one, separated from the GUI, do your business and make sure to call qApp.processEvents() regularly to keep the GUI responsive</li> <li>if you just want to communicate back with the gui: <ol> <li>define a custom <a href="http://qt-project.org/doc/qt-5/qevent.html" rel="nofollow noreferrer">QEvent</a> type</li> <li><a href="http://qt-project.org/doc/qt-5/qwidget.html#event" rel="nofollow noreferrer">subscribe to this event</a></li> <li>post your event to Qt event loop using <a href="http://qt-project.org/doc/qt-5/qcoreapplication.html#postEvent" rel="nofollow noreferrer">QCoreApplication::postEvent()</a>.</li> </ol></li> </ul></li> </ul>
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    1. POHow to integrate Boost.Asio main loop in GUI framework like Qt4 or GTK
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    1. COThe solution you suggest requires some kind of busy or short timeouts wait, that is suboptimal. I rather want merge both even loop and not run-qt/run-asio/run-qt/run-asio, especially when I wait for one of: user input/input from the network that can occure simultaniously.
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    2. COThere Ain't No Free Lunch. If I understood correctly, asio has an essential part which is calling the ::run() function, which is blocking. If that function is blocking, either you call it from a background thread, or it might block your application. You mention event loop integration but from quickly browsing, I haven't found any event loop in asio. Asynchronous calling does not necessarily go with an event loop.
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    3. COYou can also do it the other way round: use Qt for everything, and just "convert" qt network events into a format expected by asio. In this way, you would not use asio, but would have to call the legacy code in the same asio used to do.
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