title: What does QPainter::save () and QPainter::restore () do?
body: <p>I am not certain what it is that <code>QPainter</code> does when I invoke <code>save()</code> and <code>restore()</code>.</p>
  
  <p>Is it saving the image it is drawing or is it just saving information like <code>penWidth</code> and <code>color</code> etc.?<br>
  Could I use it to restore the image of a previous paint event?</p>