Sets the day width that will be used for drawing this gantt widget.
        
        :param      width | <int>

def setDayWidth(self, width):
        """
        Sets the day width that will be used for drawing this gantt widget.
        
        :param      width | <int>
        """
        self._dayWidth = width
        
        start = self.ganttWidget().dateStart()
        end = self.ganttWidget().dateEnd()
        
        self._dirty = True