(define Shape (interface () draw)) (define Rectangle (class* object% (Shape) (width height) (public [draw (lambda (dc x y) (send dc draw-rectangle x y width height))]) (sequence (super-init)))) (define Circle (class* object% (Shape) (radius) (public [draw (lambda (dc x y) (send dc draw-ellipse (- x radius) (- y radius) (* 2 radius) (* 2 radius)))]) (sequence (super-init)))) (define Translated (class* object% (Shape) (orig-shape dx dy) (public [draw (lambda (dc x y) (send orig-shape draw dc (+ x dx) (+ y dy)))]) (sequence (super-init)))) (define shape-canvas% (class canvas% (parent a-shape) (inherit get-dc) (override [on-paint (lambda () (send a-shape draw (get-dc) 0 0))]) (sequence (super-init parent)))) (define display-shape (lambda (a-shape) (unless (is-a? a-shape Shape) (error 'display-shape "expected a Shape, got: ~e" a-shape)) (let* ([frame (make-object frame% "Shapes" #f 150 150)] [panel (make-object vertical-panel% frame)] [canvas (make-object shape-canvas% panel a-shape)]) (send frame show #t)))) (define Union (class* object% (Shape) (left right) (public [draw (lambda (dc x y) (send left draw dc x y) (send right draw dc x y))]) (sequence (super-init)))) (define BB-Shape (interface (Shape) bounding-box)) (define-struct BB (left top right bottom)) (define BB-Rectangle (class* Rectangle (BB-Shape) (width height) (public [bounding-box (lambda () (make-BB 0 0 width height))]) (sequence (super-init width height)))) (define BB-Circle (class* Circle (BB-Shape) (r) (public [bounding-box (lambda () (make-BB (- r) (- r) r r))]) (sequence (super-init r)))) (define BB-Translated (class* Translated (BB-Shape) (shape dx dy) (public [bounding-box (lambda () (let ([pre-bb (send shape bounding-box)]) (make-BB (+ (BB-left pre-bb) dx) (+ (BB-top pre-bb) dy) (+ (BB-right pre-bb) dx) (+ (BB-bottom pre-bb) dy))))]) (sequence (super-init shape dx dy)))) (define BB-Union (class* Union (BB-Shape) (left right) (public [bounding-box (lambda () (let ([left-bb (send left bounding-box)] [right-bb (send right bounding-box)]) (make-BB (min (BB-left left-bb) (BB-left right-bb)) (min (BB-top left-bb) (BB-top right-bb)) (max (BB-right left-bb) (BB-right right-bb)) (max (BB-bottom left-bb) (BB-bottom right-bb)))))]) (sequence (super-init left right)))) (define shape-canvas% (class canvas% (panel shape) (inherit get-dc get-client-size) (override [on-paint (lambda () (let-values ([(win-width win-height) (get-client-size)]) (let* ([bb (send shape bounding-box)] [size (lambda (left1 right1 left2 right2) (- (/ (- (- right2 left2) (- right1 left1)) 2) left1))] [x (size (BB-left bb) (BB-right bb) 0 win-width)] [y (size (BB-top bb) (BB-bottom bb) 0 win-height)]) (send shape draw (get-dc) x y))))]) (sequence (super-init panel)))) (define display-shape (lambda (a-shape) (unless (is-a? a-shape BB-Shape) (error 'display-shape "expected a BB-Shape, got: ~e" a-shape)) (let* ([frame (make-object frame% "Centered Shapes" #f 150 150)] [canvas (make-object shape-canvas% frame a-shape)]) (send frame show #t)))) (define shape1 (make-object BB-Rectangle 40 30)) (define shape2 (make-object BB-Translated (make-object BB-Circle 20) 30 30)) (define shape3 (make-object BB-Union shape1 shape2)) (display-shape shape1) (display-shape shape2) (display-shape shape3)
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