Committed two lines from John to help fix the menus a bit.

[freeglut] / src / freeglut_callbacks.c

diff --git a/src/freeglut_callbacks.c b/src/freeglut_callbacks.c
index 90baf10..da06283 100644 (file)
--- a/src/freeglut_callbacks.c
+++ b/src/freeglut_callbacks.c
@@ -48,6 +48,9 @@
  */
 void FGAPIENTRY glutDisplayFunc( void (* callback)( void ) )
 {
+    if( !callback )
+       fgError ("Fatal error in program.  NULL display callback not "
+           "permitted in GLUT 3.0+ or freeglut 2.0.1+\n");
     SET_CALLBACK( Display );
 
     /*