title: How do you implement a snap-to-grid in QGraphicsScene? Mine didn't work
body: <p>I don't have any code to show because this was over a year ago.  I used a timer I think.  It did not work very professionally.  How would you do it so that it is a smooth operator?</p>
  
  <p>I am already able to draw the grid efficiently (ie. in view only).  I just need the snapping algorithm.</p>