title: how to mark current item text in QComboBox?
body: <p>I'm using a combo box as a simple command line with a history.</p>
  <p>Here's the signal-slot definition:</p>
  <pre><code>QtWidgets.QShortcut(QtGui.QKeySequence(QtCore.Qt.Key_Return),
                      self.comboBox_cmd,
                      activated=self.queryLine)
  </code></pre>
  <p>...and the slot:</p>
  <pre><code>@QtCore.pyqtSlot()
  def queryLine(self):
      '''
      Read cmd string from widget and write to device.
      '''
      ## comboBox can be enhanced with a history
      cmd = self.comboBox_cmd.currentText()
      cmds = [self.comboBox_cmd.itemText(i) for i in range(self.comboBox_cmd.count())]
      if not cmds or cmds[-1] != cmd:
      self.comboBox_cmd.addItem(cmd)
      self.query(cmd)
  </code></pre>
  <p>This works really well. Now, how can I mark the entire text of the current item after pressing Enter, so that I can replace the whole line if I so wish?</p>