From c9820ad6002e6952080482f1ff9220f598abc554 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Tue, 5 Feb 2013 18:43:19 +0100
Subject: [PATCH] a #f array is the null pointer

* figl/gl/types.scm (array->pointer, define-array-foreign-type): Allow
  #f to indicate a null pointer.
---
 figl/gl/types.scm | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/figl/gl/types.scm b/figl/gl/types.scm
index e6df6e3..297ea5f 100644
--- a/figl/gl/types.scm
+++ b/figl/gl/types.scm
@@ -98,11 +98,17 @@
 (define-simple-foreign-type void-* '*)
 (define-simple-foreign-type const-GLvoid-* '*)
 
+(define (array->pointer x)
+  (lambda (x)
+    (if x
+        (ffi:bytevector->pointer x)
+        ffi:%null-pointer)))
+
 (define-syntax define-array-foreign-type
   (syntax-rules ()
     ((_ name element-type)
      (define-foreign-type name '*
-       ffi:bytevector->pointer
+       array->pointer
        (lambda (x) x)))))
 
 (define-array-foreign-type GLboolean-* GLboolean)
-- 
2.20.1