line.scm

;;; ezd - easy drawing for X11 displays.
;;;
;;; The procedures in this module generate the GRAPHIC objects representing
;;; lines and points.

;*           Copyright 1990-1993 Digital Equipment Corporation
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;;; A line is generated by the following procedure.

(define (line x1 y1 x2 y2 line-width color dash)
    (make-graphic
	#f
	(lambda ()
		(let ((ux1 (user->x x1))
		      (ux2 (user->x x2))
		      (uy1 (user->y y1))
		      (uy2 (user->y y2))
		      (lw (max 1 (user->lw line-width))))
		     (list (- (min ux1 ux2) lw)
			   (- (min uy1 uy2) lw)
			   (+ (max ux1 ux2) lw)
			   (+ (max uy1 uy2) lw))))
	(if (eq? color 'clear)
	    draw-clear
	    (lambda ()
		    (xdrawline *dpy* *xwindow*
			(cv-gc (user->lw line-width) color #f dash #f #f)
			(user->x x1) (user->y y1)
			(user->x x2) (user->y y2))))
	(if (eq? color 'clear)
	    draw-clear
	    (lambda ()
		    (pscolor color)
		    (pscommand "newpath" x1 y1 "moveto" x2 y2 "lineto")
		    (psstroke (user->lw line-width) dash)))
	(lambda (minx miny maxx maxy)
		(let* ((ux1 (user->x x1))
		       (ux2 (user->x x2))
		       (uy1 (user->y y1))
		       (uy2 (user->y y2))
		       (vertical (zero? (- ux2 ux1)))
		       (bbx1 (user->x minx))
		       (bbx2 (user->x maxx))
		       (bby1 (user->y miny))
		       (bby2 (user->y maxy))
		       (dx/2 (abs (/ (- bbx1 bbx2) 2)))
		       (dy/2 (abs (/ (- bby1 bby2) 2)))
		       (mouse-x (/ (+ bbx1 bbx2) 2))
		       (mouse-y (/ (+ bby1 bby2) 2))
		       (lw/2 (/ (user->lw line-width) 2))
		       (theta (if vertical (acos 0) (atan (/ (- uy2 uy1)
							     (- ux2 ux1)))))
		       (cos-theta (cos (- theta)))
		       (sin-theta (sin (- theta))))

		      (define (rotate-x x y)
			      (- (* x cos-theta) (* y sin-theta)))

		      (define (rotate-y x y)
			      (+ (* x sin-theta) (* y cos-theta)))

		      (and (<= (- (min (rotate-x ux1 uy1) (rotate-x ux2 uy2))
				  dx/2)
			       (rotate-x mouse-x mouse-y)
			       (+ (max (rotate-x ux1 uy1) (rotate-x ux2 uy2))
				  dx/2))
			   (<= (- (min (rotate-y ux1 uy1) (rotate-y ux2 uy2))
				  dy/2 lw/2)
			       (rotate-y mouse-x mouse-y)
			       (+ (max (rotate-y ux1 uy1) (rotate-y ux2 uy2))
				  dy/2 lw/2)))))))

(define-ezd-command
    `(line ,number? ,number? ,number? ,number?
	   (optional ,non-negative?) (optional ,color?) (optional ,dash?))
    "(line x1 y1 x2 y2 [<line-width>] [<color>] [dash])"
    line)

;;; A point is generated by the following procedure.

(define (point x y color)
    (make-graphic
	#f
	(lambda ()
		(let ((ux (user->x x))
		      (uy (user->y y)))
		     (list ux uy (+ ux 1) (+ uy 1))))
	(if (eq? color 'clear)
	    draw-clear
	    (lambda ()
		    (xdrawpoint *dpy* *xwindow* (cv-gc 0 color #f #f #f #f)
			(user->x x) (user->y y))))
	(if (eq? color 'clear)
	    draw-clear
	    (lambda ()
		    (pscolor color)
		    (pscommand "newpath" x y "moveto" 0 (psypixel 1) "rlineto"
			(psxpixel 1) 0 "rlineto" 0 (- (psypixel 1)) "rlineto"
			"closepath" "fill")))
	(lambda (minx miny maxx maxy) #t)))

(define-ezd-command
    `(point ,number? ,number? (optional ,color?))
    "(point x y [<color>])"
    point)