Refreshes the button for this toolbar.

def refreshButton(self):
        """
        Refreshes the button for this toolbar.
        """
        collapsed   = self.isCollapsed()
        btn         = self._collapseButton
        
        if not btn:
            return
        
        btn.setMaximumSize(MAX_SIZE, MAX_SIZE)
        
        # set up a vertical scrollbar
        if self.orientation() == Qt.Vertical:
            btn.setMaximumHeight(12)
        else:
            btn.setMaximumWidth(12)
            
        icon = ''
        
        # collapse/expand a vertical toolbar
        if self.orientation() == Qt.Vertical:
            if collapsed:
                self.setFixedWidth(self._collapsedSize)
                btn.setMaximumHeight(MAX_SIZE)
                btn.setArrowType(Qt.RightArrow)
            else:
                self.setMaximumWidth(MAX_SIZE)
                self._precollapseSize = None
                btn.setMaximumHeight(12)
                btn.setArrowType(Qt.LeftArrow)
                
        else:
            if collapsed:
                self.setFixedHeight(self._collapsedSize)
                btn.setMaximumWidth(MAX_SIZE)
                btn.setArrowType(Qt.DownArrow)
            else:
                self.setMaximumHeight(1000)
                self._precollapseSize = None
                btn.setMaximumWidth(12)
                btn.setArrowType(Qt.UpArrow)
        
        for index in range(1, self.layout().count()):
            item = self.layout().itemAt(index)
            if not item.widget():
                continue
                
            if collapsed:
                item.widget().setMaximumSize(0, 0)
            else:
                item.widget().setMaximumSize(MAX_SIZE, MAX_SIZE)
        
        if not self.isCollapsable():
            btn.hide()
        else:
            btn.show()