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pygame debug patch / docs / reST / ref / rect.rst


Pygame uses Rect objects to store and manipulate rectangular areas. A Rect can be created from a combination of left, top, width, and height values. Rects can also be created from python objects that are already a Rect or have an attribute named "rect".

Any Pygame function that requires a Rect argument also accepts any of these values to construct a Rect. This makes it easier to create Rects on the fly as arguments to functions.

The Rect functions that change the position or size of a Rect return a new copy of the Rect with the affected changes. The original Rect is not modified. Some methods have an alternate "in-place" version that returns None but effects the original Rect. These "in-place" methods are denoted with the "ip" suffix.

The Rect object has several virtual attributes which can be used to move and align the Rect:

top, left, bottom, right
topleft, bottomleft, topright, bottomright
midtop, midleft, midbottom, midright
center, centerx, centery
size, width, height

All of these attributes can be assigned to:

rect1.right = 10
rect2.center = (20,30)

Assigning to size, width or height changes the dimensions of the rectangle; all other assignments move the rectangle without resizing it. Notice that some attributes are integers and others are pairs of integers.

If a Rect has a nonzero width or height, it will return True for a nonzero test. Some methods return a Rect with 0 size to represent an invalid rectangle.

The coordinates for Rect objects are all integers. The size values can be programmed to have negative values, but these are considered illegal Rects for most operations.

There are several collision tests between other rectangles. Most python containers can be searched for collisions against a single Rect.

The area covered by a Rect does not include the right- and bottom-most edge of pixels. If one Rect's bottom border is another Rect's top border (i.e., rect1.bottom=rect2.top), the two meet exactly on the screen but do not overlap, and rect1.colliderect(rect2) returns false.

Though Rect can be subclassed, methods that return new rectangles are not subclass aware. That is, move or copy return a new :mod:`pygame.Rect` instance, not an instance of the subclass. This may change. To make subclass awareness work though, subclasses may have to maintain the same constructor signature as Rect.