[pygame] Angle To Target Function

[Kris Schnee <kschnee@xxxxxxxxxx>]

Just thought I'd offer this function, which might be useful for
characters with following behavior. It finds the angle from one point to
another, in degrees, with 0 being "up" and 90 being "right." It's
therefore useful for deciding whether a target is to a character's right
etc., and it's easily changed if you don't like the scale I used.

------

import math
def AngleToTarget(dx,dy):
    """Returns the angle to a point (dx,xy) in degrees.

    0==up/north, 90==right/east, 180==down/south, 270==left/west.
    """
    if dx == 0: ## Special case to prevent zero-division
        if dy > 0:
            return 180
        elif dy < 0:
            return 0
        else:
            return None

    oa = float(dy)/float(dx)
    theta = math.degrees(math.atan(oa)) + 90.0

    if dx > 0:
        return theta
    else:
        return 180+theta

    return theta


## Demonstrate the function graphically: show angle from a "sun" to your
cursor.
import pygame
pygame.init()
from pygame.locals import *
s = pygame.display.set_mode((500,500))
font = pygame.font.Font(None,36)
done = False
while not done:
    for event in pygame.event.get():
        if event.type == KEYDOWN:
            done = True

    x, y = pygame.mouse.get_pos()
    dx, dy = x-250, y-250
    theta = AngleToTarget(dx,dy)
    s.fill((0,0,0))
    pygame.draw.circle(s,(255,255,64),(250,250),10)
    t = font.render(str(int(theta)),1,(255,255,255))
    pygame.draw.line(s,(128,128,128),(250,250),(x,y))
    s.blit(t,(0,0))
    pygame.display.update()