[ft-devel] Autohinter: stem darkening, first rough prototype

[Nikolaus Waxweiler]

Hi list,
so I just finished a very rough prototype for stem darkening for the 
autohinter. This is not meant for inclusion into master but rather as a 
starting point for discussion. Apply patch against master.

The code has numerous problems:
1. The function to compute how much darkening to apply is a crude 
copy-pasta of the real thing in cff/cf2font.c
2. I haven't tried to suppress all code paths that deal with emboldening 
when no-stem-darkening is set.
3. Getting at the necessary stdVW proved tricky, since there isn't just 
one number somewhere that I can use. Each time a glyph is to be 
displayed, a different writing system/script analyzer could run 
producing different widths. The first few glyph-indices in 
SourceSansPro-R for example prompt the CJK-analyzer for whatever reason. 
I worked around this by simply using the biggest width any analyzer 
produces, because in my limited testing, that value usually wasn't far 
off the mark.
4. There is a definitive performance hit. Using 'ftview 16 
VL-Gothic-Regular.ttf' and keeping the down-key pressed to eventually 
render all of its' 16713 glyphs is quite smooth without hinting but very 
sluggish with the emboldening autohinter. Much less so without emboldening.
5. The results look crappy without gamma correction ;) Use the pixman 
patch in the other thread if you want to give it a test drive in 
real-world-apps like Firefox.

Please have a look and tell me what you think :)

Best regards,
Nikolaus