title: How to resize QPushButton according to the size of it's icon?
body: <p>I need the flat QPushButton with icon. 
  The problem is the size of the button is much bigger than the size of icon.
  Is there a way to set the size of button according to the size of icon, without using magic numbers: </p>
  
  <pre><code>QIcon icon = GetIcon();
  QPushButton* btn = new QPushButton( icon, "" ); 
  btn-&gt;setFlat( true );
  btn-&gt;setCheckable( true );
  
  btn-&gt;setFixedSize( 16, 16 ); // These values should be calculated from the icon size.
  </code></pre>