Set a colored frame around the FigureCanvas if highlight is True.

def highlight_canvas(self, highlight):
        """
        Set a colored frame around the FigureCanvas if highlight is True.
        """
        colorname = self.canvas.palette().highlight().color().name()
        if highlight:
            self.canvas.setStyleSheet(
                    "FigureCanvas{border: 1px solid %s;}" % colorname)
        else:
            self.canvas.setStyleSheet("FigureCanvas{}")