title: emit SIGNAL when GUI Thread is idle in Qt?
body: <p>I have <em>GUI</em> Thread which creates &amp; manages the <em>GUI</em> content. Now when the application is idle i.e. all threads are idle (or even if only the GUI thread is idle) then I want my <code>QMainWindow</code> inherited class's object to emit a <code>SIGNAL</code>. So that whenever the Application is idle I will silently create the <code>Widgets</code> required for the next stage. So I would like to know how do I make that object to emit a <code>SIGNAL</code> whenever the <em>GUI</em> Thread is idle? My Application is <em>multi-threaded</em> &amp; has multiple classes, so it is not necessary that the <code>SIGNAL</code> is emitted in the <em>GUI</em> class only.
  Also the <code>SIGNAL</code> should not be emitted as soon as the thread becomes idle. I want that the thread should be idle for a sufficient amount of time so that I am sure that the user is actually idling.
  Thank You!</p>