title: QPlainTextEdit force redraw
body: <p>I'd like to force a redraw over a QPlainTextEdit widget, because my highlighting rules changed. However, all lines and blocks aren't redrawn, respecting the new rules.</p>
  
  <p>This is true because if I modify a line, the correct highlighting is applied, and I am happy. But I cannot force-modify each block to see any change!</p>
  
  <p>Is there a way to force a redraw? I tried update() and similars, but nothing seems to work.</p>
  
  <p>Thanks!</p>