[ft-devel] Stem darkening of new CFF engine

[octoploid]

On my system the stem darkening of the new CFF engine
is too aggressive. Normal weight fonts look almost bold
when it is enabled.

Currently I use the following hack:
diff --git a/src/cff/cf2font.c b/src/cff/cf2font.c
index 479d912..f2157a7 100644
--- a/src/cff/cf2font.c
+++ b/src/cff/cf2font.c
@@ -108,18 +108,18 @@
        *
        */
       if ( scaledStem < cf2_intToFixed( 500 ) )
-        *darkenAmount = FT_DivFix( cf2_intToFixed( 400 ), ppem );
+        *darkenAmount = FT_DivFix( cf2_intToFixed( 300 ), ppem );
 
       else if ( scaledStem < cf2_intToFixed( 1000 ) )
-        *darkenAmount = FT_DivFix( cf2_intToFixed( 525 ), ppem ) -
+        *darkenAmount = FT_DivFix( cf2_intToFixed( 425 ), ppem ) -
                           FT_MulFix( stemWidthPer1000,
                                      cf2_floatToFixed( .25 ) );
 
       else if ( scaledStem < cf2_intToFixed( 1667 ) )
-        *darkenAmount = FT_DivFix( cf2_intToFixed( 275 ), ppem );
+        *darkenAmount = FT_DivFix( cf2_intToFixed( 175 ), ppem );
 
       else if ( scaledStem < cf2_intToFixed( 2333 ) )
-        *darkenAmount = FT_DivFix( cf2_intToFixed( 963 ), ppem ) -
+        *darkenAmount = FT_DivFix( cf2_intToFixed( 863 ), ppem ) -
                           FT_MulFix( stemWidthPer1000,
                                      cf2_floatToFixed( .413 ) );
 
and the results look much more pleasing.

Wouldn't it be a good idea to make the amount of darkening user
configurable? (Maybe by specifying a number from 0..10 at compile
time (0=no darkening ... 10=full darkening))