title: How to make Qt work when main thread is busy?
body: <p>Main (function main is there) thread of my program is reserved for non-GUI tasks. It calls a number of lengthy calculation functions.  All implemented GUI's have been doing their work in a separate threads.</p>
  
  <p>I'm now going to implement one more GUI using Qt. <a href="https://doc.qt.io/qt-5/qapplication.html#exec" rel="noreferrer">Qt documentation</a> says all GUI related tasks should be done in main thread.
  In my case, inserting occasional QCoreApplication::processEvents() calls in main thread would be virtually useless due to great delays between them.</p>
  
  <p>Is there any way to overcome this constraint of Qt? 
  Is it impossible to do something non-GUI related in main thread of Qt program?</p>