shithub: freetype+ttf2subf

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Expand comment (cont'd).

git/fs: mount .git/fs: mount/attach disallowed

--- a/src/smooth/ftgrays.c

+++ b/src/smooth/ftgrays.c

@@ -380,6 +380,12 @@

   /* each slanted line.  Nevertheless, these divisions are noticeable  */

   /* in the overall performance because flattened curves produce a     */

   /* very large number of slanted lines.                               */

+  /*                                                                   */

+  /* The division results here are always within ONE_PIXEL.  Therefore */

+  /* the shift magnitude should be at least PIXEL_BITS wider than the  */

+  /* divisors to provide sufficient accuracy of the multiply-shift.    */

+  /* It should not exceed (64 - PIXEL_BITS) to prevent overflowing and */

+  /* leave enough room for 64-bit unsigned multiplication however.     */

 #define FT_UDIVPREP( c, b )                                                 \

   FT_Int64  b ## _r = c ? (FT_Int64)( ~(FT_UInt64)0 >> PIXEL_BITS ) / ( b ) \

                     : 0