title: PyQt4 mouse move event: find widget
body: <p>How can I find over which widget is the event fired? The position is relative to origin of whatever widget is underneath it. I want to constrain the event to only one wiget.</p>
  
  <pre><code>def eventFilter(self, source, event):
      if event.type() == QtCore.QEvent.MouseMove:
          if event.buttons() == QtCore.Qt.NoButton:
              pos = event.pos()
              self.statusbar.showMessage("mouse tracked at {} x {}".format(pos.x(), pos.y()))
              print(dir(event))
              # self.edit.setText('x: %d, y: %d' % (pos.x(), pos.y()))
      return QtGui.QMainWindow.eventFilter(self, source, event)
  </code></pre>