title: QPainter: adding padding
body: <p>Is there a way to easily add padding to a QPainter area?</p>
  
  <p>The whole idea is to have a border, within the drawable area, where I can't draw so that when I draw a line from (0, 0) to (10, 10) I'm actually drawing at (0 + padding, 0 + padding) to (10 + padding, 10 + padding). The padding border should be seen though.</p>
  
  <p>Assuming a <code>QPainter</code> is created as:</p>
  
  <pre><code>QPainter painter(aWidget); // aWIdget is a Widget*
  </code></pre>
  
  <p>and a <code>padding</code> integer variable. Now let's consider the area that is drawable of the widget as "A". How can I get to have a drawable area "B", so that B has:</p>
  
  <pre><code>B_width = A_width - 2 * padding;
  B_height = A_height - 2 * padding;
  </code></pre>
  
  <p>and what would have been at QPoint(padding, padding) in A would now be at QPoint(0, 0) in B?</p>
  
  <p>I began to implement it by my own (which is going to be painful), but I was wondering if there way an easier and "pre-made" way to do this in Qt? Maybe Transformations?</p>
  
  <p>Thanks.</p>