glFlush to ensure graphics are visible

recipes/neverball/redox.patch

 diff -ruwN source/Makefile source-new/Makefile
 --- source/Makefile	2019-08-07 22:16:07.630185664 -0600
-+++ source-new/Makefile	2019-08-07 22:48:03.915634667 -0600
++++ source-new/Makefile	2019-08-09 21:41:20.296942596 -0600
 @@ -38,11 +38,11 @@
  ifeq ($(DEBUG),1)
  	CFLAGS   := -g
@@ -73,3 +73,15 @@ diff -ruwN source/Makefile source-new/Makefile
  
  $(BALL_TARG) : $(BALL_OBJS)
  	$(LINK) -o $(BALL_TARG) $(BALL_OBJS) $(LDFLAGS) $(ALL_LIBS)
+diff -ruwN source/share/video.c source-new/share/video.c
+--- source/share/video.c	2014-05-21 07:21:43.000000000 -0600
++++ source-new/share/video.c	2019-08-09 21:41:42.891178826 -0600
+@@ -359,6 +359,8 @@
+ 
+     snapshot_take();
+ 
++    glFlush();
++
+     SDL_GL_SwapWindow(window);
+ 
+     /* Accumulate time passed and frames rendered. */