[pygame] PCR: subtract rectangles

[Gerrit Holl <gerrit@nl.linux.org>]

Hi,

attached is a code snippet to subtract rectangles.

Gerrit.

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import pygame

def coor2rect(c):
    """Converts ((x,y),(x,y)) style coords to a Rect object"""
    topx = min(c[0][0], c[1][0])
    bottomx = max(c[0][0], c[1][0])
    topy = min(c[0][1], c[1][1])
    bottomy = max(c[0][1], c[1][1])
    size = (bottomx-topx, bottomy-topy)
    return pygame.rect.Rect([topx, topy, size[0], size[1]])

def subtractrect(outer, inner):
    """Subtract inner rectangle from outer rectangle.

    This function takes as arguments two rectangles, and
    returns a list of rectangles covering all areas covered
    by the outer rectangle but not by the inner rectangle.
    The inner rectangle must reside entirely inside the outer
    rectangle. This function always returns a list of 4 rectangles.
    If outer == inner, all rectangles have size 0. This function
    tries to distribute the uncovered area's fairly over the
    4 rectangles.

    This function uses the coor2rect() function, so that one
    is included in the same code snippet.
    """

    if not outer.contains(inner):
        raise ValueError("rect1 must contain rect2")
    coords = []
    coords.append((outer.topleft, inner.topright))
    coords.append(((inner.right, outer.top), (outer.right, inner.bottom)))
    coords.append((inner.bottomleft, outer.bottomright))
    coords.append(((outer.left, inner.top), (inner.left, outer.bottom)))
    return [coor2rect(i) for i in coords]