def _sanity_check_scale(self, scale_x, scale_y):
        """Do a sanity check on the proposed scale vs. window size.
        Raises an exception if there will be a problem.
        """
        win_wd, win_ht = self.get_window_size()
        if (win_wd <= 0) or (win_ht <= 0):
            raise ImageViewError("window size undefined")

        # final sanity check on resulting output image size
        if (win_wd * scale_x < 1) or (win_ht * scale_y < 1):
            raise ValueError(
                "resulting scale (%f, %f) would result in image size of "
                "<1 in width or height" % (scale_x, scale_y))

        sx = float(win_wd) / scale_x
        sy = float(win_ht) / scale_y
        if (sx < 1.0) or (sy < 1.0):
            raise ValueError(
                "resulting scale (%f, %f) would result in pixel size "
                "approaching window size" % (scale_x, scale_y))
Do a sanity check on the proposed scale vs. window size.
        Raises an exception if there will be a problem.