docs: def paintEvent(self, event):
          """
          Pains the messages and the visible area on the panel.
          :param event: paint event infos
          """
          if self.isVisible():
              # fill background
              self._background_brush = QtGui.QBrush(self.editor.background)
              painter = QtGui.QPainter(self)
              painter.fillRect(event.rect(), self._background_brush)
              self._draw_messages(painter)
              self._draw_visible_area(painter)