title: Why do my my line widths looks different in a QGraphicsScene with the same QPen width?
body: <p>I use a <code>QPainter</code> to draw my widget with this code:</p>
  
  <pre><code>QPen pen(Qt::black, 0.6, Qt::SolidLine);
  QPainter painter(this);
  painter.setPen(pen);
  
  // vertical 
  painter.drawLine(startX,0,startX,50);
  painter.drawLine((startX += grid),0,startX,50);
  painter.drawLine((startX += grid),0,startX,50);
  painter.drawLine((startX += grid),0,startX,50);
  painter.drawLine((startX += grid),0,startX,50);
  painter.drawLine((startX += grid),0,startX,50);
  
  // horizontal 
  pen.setWidth(0.7);
  painter.setPen(pen);
  painter.drawLine(0,grid*2,70,grid*2);
  painter.drawLine(0,grid*4,70,grid*4);
  painter.drawLine(0,grid*6,70,grid*6);
  painter.drawLine(0,grid*8,70,grid*8);
  </code></pre>
  
  <p>When I add this item into a <code>QGraphicsScene</code>, the width of the lines sometimes look different from each other, especially when I zoom in. Can anyone explain why this is happening and what can be done to fix it?</p>
  
  <p>This screen shot demonstrates the problem:</p>
  
  <p><img src="https://i.stack.imgur.com/XJxDo.jpg" alt="enter image description here"></p>