; Test whether a line on the screen is being selected by the mouse.
; (gldefun draw-line-selectedp (d\:draw-line pt\:vector off\:vector)
;   (let ((ptp (pt - off)))
;     (and (contains? (vregion d) ptp)         ; is point in region near line
;          ((distance (line d) ptp) <  5) ) ))  ; and within distance of 5
(defun t6 (D PT OFF)
  (LET ((PTP (LIST (- (CAR (PROG1 PT)) (CAR (PROG1 OFF)))
                   (- (CADR (PROG1 PT)) (CADR (PROG1 OFF))))))
       (AND (AND (> = (CAR (PROG1 PTP))
                     (- (MIN (CAR (CADR (PROG1 D)))
                             (+ (CAR (CADR (PROG1 D)))
                                (CAR (CADDR (PROG1 D)))))
                        2))
                 (< = (CAR (PROG1 PTP))
                     (+ (- (MIN (CAR (CADR (PROG1 D)))
                                (+ (CAR (CADR (PROG1 D)))
                                   (CAR (CADDR (PROG1 D)))))
                           2)
                        (+ (ABS (CAR (CADDR (PROG1 D)))) 4)))
                 (> = (CADR (PROG1 PTP))
                     (- (MIN (CADR (CADR (PROG1 D)))
                             (+ (CADR (CADR (PROG1 D)))
                                (CADR (CADDR (PROG1 D)))))
                        2))
                 (< = (CADR (PROG1 PTP))
                     (+ (- (MIN (CADR (CADR (PROG1 D)))
                                (+ (CADR (CADR (PROG1 D)))
                                   (CADR (CADDR (PROG1 D)))))
                           2)
                        (+ (ABS (CADR (CADDR (PROG1 D)))) 4))))

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