using new grid overlay mechanism for speed up with Cairo graphics
using new grid overlay mechanism for speed up with Cairo graphics

walterbender/turtleart,walterbender/turtleflags,walterbender/turtle3D,walterbender/AmazonasTortuga,walterbender/turtleartmini,AlanJAS/turtleart,walterbender/turtleconfusion