[ft-devel] empirical correction to the patch to gray_render_cubic

[Graham Asher]

The patch to gray_render_cubic that I suggested, and which evolved a 
little after some discussion, appears to be too aggressive in its 
reduction of the number of passes through the spline-splitting loop. 
Circles now have noticeable corners. Here is an improvement that fixes 
the situation. It is empirical only and does not yet rest on theory. 
Change this code in gray_render_cubic from

   while ( dx > 0 )
   {
     dx >>= 3;
     level++;
   }

to

   while ( dx > 0 )
   {
     dx >>= 2;
     level++;
   }

The difference is that dx is now shifted right by 2, not 3, on each 
pass. I attach before (left) and after (right) screen shots, taken from 
a CartoType map, that show the difference. The slight difference in 
scales in the images is due to my haste.

Best regards,

Graham