I want to draw some triangles in my widget pointing up: ie. two vertices are on the same horizontal line and a third vertex halfway between these two points and above.

When the triangle is not filled the top vertex is "sharp" but when I draw the triangle filled, it does not have a "sharp" point: an extra diagonal line of pixels is added on the left side, outside of the triangle.

Qt Code: 
  1. void widget::paintEvent(QPaintEvent *)
  2. {
  3.   QPainter p(this);
  4.  
  5.   p.setPen(Qt::black);
  6.   p.setBrush(Qt::black);
  7.  
  8.   int halfwidth = 7;
  9.   int height = 7;
  10.  
  11.   QPolygon triangle;
  12.  
  13.   triangle.clear();
  14.   triangle << QPoint(10+halfwidth, 10-height);
  15.   triangle << QPoint(10, 10);
  16.   triangle << QPoint(10+2*halfwidth, 10);
  17.   p.drawPolygon(triangle);
  18. }
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unfill-vs-fill-zoom.png

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