def __call__(self, left, right):
"""detect collision between two sprites using scaled circles
pygame.sprite.collide_circle_radio(ratio)(left, right): return bool
Tests for collision between two sprites by testing whether two circles
centered on the sprites overlap after scaling the circle's radius by
the stored ratio. If the sprites have a "radius" attribute, that is
used to create the circle; otherwise, a circle is created that is big
enough to completely enclose the sprite's rect as given by the "rect"
attribute. Intended to be passed as a collided callback function to the
*collide functions. Sprites must have a "rect" and an optional "radius"
attribute.
"""
ratio = self.ratio
xdistance = left.rect.centerx - right.rect.centerx
ydistance = left.rect.centery - right.rect.centery
distancesquared = xdistance ** 2 + ydistance ** 2
if hasattr(left, "radius"):
leftradius = left.radius * ratio
else:
leftrect = left.rect
leftradius = ratio * 0.5 * ((leftrect.width ** 2 + leftrect.height ** 2) ** 0.5)
# store the radius on the sprite for next time
setattr(left, 'radius', leftradius)
if hasattr(right, "radius"):
rightradius = right.radius * ratio
else:
rightrect = right.rect
rightradius = ratio * 0.5 * ((rightrect.width ** 2 + rightrect.height ** 2) ** 0.5)
# store the radius on the sprite for next time
setattr(right, 'radius', rightradius)
return distancesquared <= (leftradius + rightradius) ** 2
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