title: Updating progress bar during copying a large file size
body: <p>How to update the progress bar to show the progress of copying a file because <code>QFile</code> documentation says: </p>
  
  <blockquote>
    <p>Unlike other <code>QIODevice</code> implementations, such as <code>QTcpSocket</code>, <code>QFile</code> does
    not emit the <code>aboutToClose()</code>, <code>bytesWritten()</code>, or <code>readyRead()</code> signals.
    This implementation detail means that <code>QFile</code> is not suitable for
    reading and writing certain types of files, such as device files on
    Unix platforms.</p>
  </blockquote>
  
  <p>I would greatly appreciate any help on this.</p>