def METHOD_NAME(self, ctx, ra, dist, drawp):
    """Draw (if drawp) or move to the appropriate place on the screen
       for the given ra and dist coordinates.
    """
    x = dist * self.dist_scale * math.cos(ra) + self.halfwidth
    y = dist * self.dist_scale * math.sin(ra) + self.halfheight
    if drawp:
        ctx.line_to(x, y)
    else:
        ctx.move_to(x, y)