[ft-devel] ttfautohint & x-heights

[vern adams]

The launch of Adobe's 'Source Sans' type family has allowed me to run some 
'like for like' tests of ttfautohint instructions against proffesional-level 
manual instructions. Source Sans seems very well instructed, so it's a great 
tool for testing ttfautohint.

One difference i notice (again) is that at small size ranges (eg. 8-12pts) the 
ttfautohinted font renders the x-height 1 pixel higher than the pro-level 
manually hinted font.
I have posted screenshots & a brief explanation at http://goo.gl/hsxZr

I would like to suggest that ttfautohint should be able to produce x-heights at 
the height same as the manually hinted font. I think this difference is due to 
ttfautohint/freetype snapping the x-height 'up' to the nearest pixel edge, 
whereas when manually hinting the designer as allowed the x-height to snap 
'down' to the nearest pixel edge?

At the moment ttfautohint can increase the x-height by using the -x argument, 
but switching this feature off (-x 0) still increases x-height compared to the 
original instructions. Would it be possible for ttfautohint to decrease the 
x-height snapping by 1px at particular size range? :)

-vern