title: Draw circle with hole by using MKOverlayRenderer does not work well
body: <p>I'd like to draw circle with hole (like donut) on mapview.
  my code is here.</p>
  
  <pre><code>- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CG    ContextRef)context {
  
  WPCircleOverlay * circleOverlay = self.overlay;
  
  CGPoint centerPoint = [self pointForMapPoint:MKMapPointForCoordinate(circleOverlay.coordinate)];
  
  CGFloat innerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.innerRadius;
  CGFloat outerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.outerRadius;
  CGMutablePathRef path = CGPathCreateMutable();
  
  //CGPathMoveToPoint(path, ...);
  CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, outerRadius, 0, 2 * M_PI, true);
  CGPathCloseSubpath(path);
  
  // Add the inner arc to the path (later used to substract the inner area)
  CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, innerRadius, 0, 2 * M_PI, true);
  CGPathCloseSubpath(path);
  
  // Add the path to the context
  CGContextAddPath(context, path);
  
  CGContextSetFillColorWithColor(context, self.fillColor.CGColor);
  CGContextEOFillPath(context);
  
  CGPathRelease(path);
  </code></pre>
  
  <p>It works well in simulator, but on device it doesn't.</p>
  
  <p>On device, outer circle is filled with color, and inner circle wasn't clipped.
  How can I modify my code to work well on device?</p>