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;;; guile-2d
;;; Copyright (C) 2013, 2014 David Thompson <dthompson2@worcester.edu>
;;;
;;; This program is free software: you can redistribute it and/or
;;; modify it under the terms of the GNU General Public License as
;;; published by the Free Software Foundation, either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; Rects are axis-aligned bounding boxes that can be used for
;; performing simple collision detection.
;;
;;; Code:
(define-module (2d rect)
#:use-module (srfi srfi-9)
#:use-module (2d vector2)
#:export (<rect>
make-rect
null-rect
rect?
rect-x
rect-y
rect-left
rect-right
rect-top
rect-bottom
rect-position
rect-top-left
rect-top-right
rect-bottom-left
rect-bottom-right
rect-center-x
rect-center-y
rect-center
rect-half-width
rect-half-height
rect-width
rect-height
rect-size
rect-move
rect-inflate
rect-union
rect-clip
rect-within?
rect-intersects?
rect-contains?))
;;;
;;; Rectangles
;;;
;; The rect API is very similar to the Pygame rect API, but rects are
;; immutable.
(define-record-type <rect>
(%make-rect x y width height)
rect?
(x rect-x)
(y rect-y)
(width rect-width)
(height rect-height))
(define make-rect
(case-lambda
((x y width height)
(%make-rect x y width height))
((position size)
(%make-rect (vx position) (vy position)
(vx size) (vy size)))))
(define null-rect (make-rect 0 0 0 0))
(define (rect-right rect)
(+ (rect-x rect) (rect-width rect)))
(define rect-left rect-x)
(define rect-top rect-y)
(define (rect-bottom rect)
(+ (rect-y rect) (rect-height rect)))
(define (rect-position rect)
"Return the top-left corner of RECT as a vector2."
(vector2 (rect-x rect)
(rect-y rect)))
(define rect-top-left rect-position)
(define (rect-top-right rect)
(vector2 (rect-right rect)
(rect-top rect)))
(define (rect-bottom-left rect)
(vector2 (rect-left rect)
(rect-bottom rect)))
(define (rect-bottom-right rect)
(vector2 (rect-right rect)
(rect-bottom rect)))
(define (rect-center-x rect)
(+ (rect-x rect) (rect-half-width rect)))
(define (rect-center-y rect)
(+ (rect-y rect) (rect-half-height rect)))
(define (rect-center rect)
(vector2 (rect-center-x rect)
(rect-center-y rect)))
(define (rect-half-width rect)
(/ (rect-width rect) 2))
(define (rect-half-height rect)
(/ (rect-height rect) 2))
(define (rect-size rect)
"Return the size of RECT as a vector2."
(vector2 (rect-width rect)
(rect-height rect)))
(define (%rect-move rect x y)
"Move RECT by the offset X, Y."
(make-rect (+ (rect-x rect) x)
(+ (rect-y rect) y)
(rect-width rect)
(rect-height rect)))
(define rect-move
(case-lambda
"Create a new rectangle by moving RECT by the given
offset. rect-move accepts a vector2 or x and y coordinates as separate
arguments."
((rect v)
(%rect-move rect (vx v) (vy v)))
((rect x y)
(%rect-move rect x y))))
(define (%rect-inflate rect width height)
"Grows the rect by the given amount. The rect stays centered around
its current center."
(make-rect (+ (rect-x rect) (/ width 2))
(+ (rect-y rect) (/ height 2))
(+ (rect-width rect) width)
(+ (rect-height rect) height)))
(define rect-inflate
(case-lambda
"Create a new rectangle by growing RECT by the given amount
without changing the center point. rect-inflate accepts a vector2 or x
and y coordinates as separate arguments."
((rect v)
(%rect-inflate rect (vx v) (vy v)))
((rect x y)
(%rect-inflate rect x y))))
(define (rect-union rect1 rect2)
"Return a rect that covers the area of RECT1 and RECT2."
(let ((x1 (min (rect-left rect1) (rect-left rect2)))
(x2 (max (rect-right rect1) (rect-right rect2)))
(y1 (min (rect-top rect1) (rect-top rect2)))
(y2 (max (rect-bottom rect1) (rect-bottom rect2))))
(make-rect x1 y1 (- x2 x1) (- y2 y1))))
(define (rect-clip rect1 rect2)
"Return the overlapping region of RECT1 and RECT2. If the rects do
not overlap, a rect of size 0 is returned."
(let ((x1 (max (rect-left rect1) (rect-left rect2)))
(x2 (min (rect-right rect1) (rect-right rect2)))
(y1 (max (rect-top rect1) (rect-top rect2)))
(y2 (min (rect-bottom rect1) (rect-bottom rect2))))
(make-rect x1 y1 (max (- x2 x1) 0) (max (- y2 y1) 0))))
(define (rect-within? rect1 rect2)
"Return #t if RECT2 is completely within RECT1."
(and (>= (rect-left rect2) (rect-left rect1))
(<= (rect-right rect2) (rect-right rect1))
(>= (rect-top rect2) (rect-top rect1))
(<= (rect-bottom rect2) (rect-bottom rect1))))
(define (rect-intersects? rect1 rect2)
"Return #t if RECT2 overlaps RECT1."
(and (< (rect-left rect1) (rect-right rect2))
(> (rect-right rect1) (rect-left rect2))
(< (rect-top rect1) (rect-bottom rect2))
(> (rect-bottom rect1) (rect-top rect2))))
(define (%rect-contains? rect x y)
(and (>= x (rect-left rect))
(<= x (rect-right rect))
(>= y (rect-top rect))
(<= y (rect-bottom rect))))
(define rect-contains?
(case-lambda
"Return #t if the given point is within RECT."
((rect v)
(%rect-contains? rect (vx v) (vy v)))
((rect x y)
(%rect-contains? rect x y))))
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