formatting requirement on data value

[dougtsai]

while mouse hovering the die, display text of die value doesn't formatting.

I try to modify it at wm_core.py.

        # lookup the die value
        grid = "x{}y{}"
        die_grid = grid.format(dc_x, dc_y)
        try:
            die_val = "{:.3f}".format(self.xyd_dict[die_grid])
	    #die_val = self.xyd_dict[die_grid]
        except KeyError:
            die_val = "N/A"