title: QWidget update events but no visual update
body: <p>Using Qt4.8 on a Mint Linux 12, I implemented a simple window containing a <code>QTableView</code> to show contents of a model. The model data is continually updated (log messages) and the <code>dataChanged()</code> signal is emitted on a regular basis (i.e. every 100ms).</p>
  
  <p>The problem I see is stuttering visual updates on the table.</p>
  
  <p>I installed an event filter on the window that counts <code>updateRequest</code>-type events, which should trigger a widget repaint (also on child widgets, i.e. the <code>tableView</code>). These come in with an average time of ~170ms between them and a standard deviation of ~90ms (which is rather large, I guess). However, the perceived visual update rate is only two or three times a second and I wonder why. It seems that not all <code>updateRequest</code> events trigger a widget repaint or that the window system swallows visual updates.</p>
  
  <p>As a second test, I forced the window to update itself by calling <code>repaint</code> or <code>update</code> every 100ms. Using <code>repaint</code>, I saw a corresponding increase in <code>updateRequest</code>-type events and a decrease of the standard deviation of the gaps; with <code>update</code>, the number did not increase. However, there was only a moderate increase of perceived update rate in both cases.</p>
  
  <p>Also: Is there a good method to measure how often a widget is actually really repainted without having to overload its <code>paintEvent</code> handler? Maybe something from <code>QTest</code>?</p>
  
  <hr>
  
  <p><strong>Update:</strong> I extended my event filter to also catch <code>paintEvent</code>-type events. There are only a one-digit number of those versus > 1000 <code>updateRequest</code>-type events.</p>