title: QWidget::mouseMoveEvent not firing when cursor over child widget
body: <p>I'm trying to capture the cursor coordinates as the mouse is moved within a <code>QWidget</code> by reimplementing <code>QWidget::mouseMoveEvent()</code>. With mouse tracking enabled, mouse move events are generated as I move the cursor around the main widget. However, when the cursor is placed over a child widget the mouse move events cease to fire.</p>
  
  <p>Mouse press/release events work while the cursor is over the same child widget, and move events are firing correctly if the mouse button is held. I've tried enabling mouse tracking on the children too, but it doesn't seem to make a difference. <strong>How can I trigger mouse move events when the mouse is over a child widget?</strong></p>
  
  <p>Here's a minimum working example that demonstrates the problem:</p>
  
  <pre><code>import sys
  from PyQt4 import QtCore, QtGui
  
  class MyWindow(QtGui.QWidget) :
      def __init__(self):
          QtGui.QWidget.__init__(self)
          tabs = QtGui.QTabWidget()
          tab1 = QtGui.QWidget()
          tab2 = QtGui.QWidget()
          tabs.addTab(tab1, "Tab 1")
          tabs.addTab(tab2, "Tab 2")
          layout = QtGui.QVBoxLayout()
          layout.addWidget(tabs)
          self.setLayout(layout)
          self.setMouseTracking(True)
  
      def mouseMoveEvent(self, event):
          print 'mouseMoveEvent: x=%d, y=%d' % (event.x(), event.y())
  
  
  app = QtGui.QApplication(sys.argv)
  window = MyWindow()
  window.setFixedSize(640, 480)
  window.show()
  sys.exit(app.exec_())
  </code></pre>
  
  <p>When the mouse is moved outside of the <code>QTabWidget</code> the mouse coordinates are printed as expected. Inside of it nothing happens unless the mouse button is held.</p>