title: Intercepting mousePressEvent on Child widget (qt)
body: <p>I'm trying to implement the following functionality based on QPlainTextEdit - by default it should show a "please enter something here" message, on click, it would vanish and allow editing.</p>
  
  <p>To do so I need to intercept whether the widget has been clicked. Can I do so without sub classing QPlainTextEdit?</p>
  
  <p>Can the parent's widget onMousePressEvent obtain which child's widget the event belongs to?</p>