Compass widget

On the #pyqt channel on Freenode, epifanio was creating a compass widget. Although he eventually decided to use Graphics View for this, the following code could be used as the starting point for a simple custom widget with a custom signal and a property for controlling the angle.

   1 import sys
   2 from PyQt4.QtCore import *
   3 from PyQt4.QtGui import *
   4 
   5 class CompassWidget(QWidget):
   6 
   7     angleChanged = pyqtSignal(float)
   8     
   9     def __init__(self, parent = None):
  10     
  11         QWidget.__init__(self, parent)
  12         
  13         self._angle = 0.0
  14         self._margins = 10
  15         self._pointText = {0: "N", 45: "NE", 90: "E", 135: "SE", 180: "S",
  16                            225: "SW", 270: "W", 315: "NW"}
  17     
  18     def paintEvent(self, event):
  19     
  20         painter = QPainter()
  21         painter.begin(self)
  22         painter.setRenderHint(QPainter.Antialiasing)
  23         
  24         painter.fillRect(event.rect(), self.palette().brush(QPalette.Window))
  25         self.drawMarkings(painter)
  26         self.drawNeedle(painter)
  27         
  28         painter.end()
  29     
  30     def drawMarkings(self, painter):
  31     
  32         painter.save()
  33         painter.translate(self.width()/2, self.height()/2)
  34         scale = min((self.width() - self._margins)/120.0,
  35                     (self.height() - self._margins)/120.0)
  36         painter.scale(scale, scale)
  37         
  38         font = QFont(self.font())
  39         font.setPixelSize(10)
  40         metrics = QFontMetricsF(font)
  41         
  42         painter.setFont(font)
  43         painter.setPen(self.palette().color(QPalette.Shadow))
  44         
  45         i = 0
  46         while i < 360:
  47         
  48             if i % 45 == 0:
  49                 painter.drawLine(0, -40, 0, -50)
  50                 painter.drawText(-metrics