title: Custom Qt QGraphicsItem tooltip
body: <p>I'm looking for some ways to implement a simple custom tooltip for <code>QGraphicsItem</code>.</p>
  
  <p>I know that I can use <code>setToolTip</code> to set text for tooltip. Now what I want is to change the text dynamically when the mouse hovers at different parts of a <code>QGraphicsItem</code> object.</p>
  
  <p>What I'm thinking to do is when I get an event <code>QEvent::ToolTip</code>, I change the tooltip text in that event handler. However, I cannot find an event function that recieve <code>QEvent::ToolTip</code> for <code>QGraphicsItem</code>.</p>
  
  <p>Or is there some ways to handle an event that mouse hovers for 2 seconds.</p>
  
  <p>How can I make it?</p>