hello-world from Chicken Scheme with Box2D

gistfile1.scm

(require-extension coops bind cplusplus-object )

#>
#include <Box2D.h>
// is there a way to access c++ class-fields without these
// two silly helpers?
float getBodyPositionX (b2Body* b) { return b->GetPosition ().x; }
float getBodyPositionY (b2Body* b) { return b->GetPosition ().y; }
<#

; Box2D.scm must be modified: remove constructor and desctuctors of
; private ones (body, fixtures)
(include "Box2D.scm")

(bind "float getBodyPositionX(b2Body* b);")
(bind "float getBodyPositionY(b2Body* b);")

(define (getBodyY obj)
  (getBodyPositionY (slot-value obj 'this)))
(define (getBodyX obj)
  (getBodyPositionX (slot-value obj 'this)))
(define (pointer obj)
  (slot-value obj 'this))
(define (my-new . args) (apply new args))

(define gravity (make-b2Vec2 0 1 ))
(define world (my-new <b2World> gravity))

(print "gravity is " (b2Vec2-x gravity) ", " (b2Vec2-y gravity))
(print "world is " world)

(define groundBodyDef (apply make-b2BodyDef '(2 ; type
                                              0 ;ang
                                              0 ;ang vel
                                              0 ; lin damp
                                              0 ; ang damp
                                              #t ; sleepable
                                              #t ;awake
                                              #f ; fixed rot
                                              #f ; bullet
                                              #t ; active
                                              #f ;userdata
                                              1 ; grav scale
                                              
                                              )))

(define boxBody (CreateBody world groundBodyDef))

(define boxShape (my-new <b2PolygonShape> ))
(SetAsBox boxShape 10 10 (make-b2Vec2 0 0) 0)

(CreateFixture boxBody boxShape 0)

(let loop ([ n 30000])
  (if (> n 0)
      (begin
        (Step world (/ 1 60) 6 1)
        (print "body pos = " (getBodyPositionY (pointer boxBody)))
        (loop (sub1 n)))))

(repl)

(delete world)
;(SetGravity world (make-b2Vec2 0 -1))