Move drawing code to it's own module and simplify draw interface

engine/math.scm

@@ -27,6 +27,12 @@
 (define (approx-= x y)
   (< (abs (- x y)) (*float-precision*)))
 
+;; Somewhat reliable fixnum conversion
+(export number->integer)
+(define (number->integer number)
+  (assert (number? number))
+  (inexact->exact (round number)))
+
 ;; Vector exports
 (export vec vec? vec2? v-x
 	set-v-x! v-y set-v-y!)