[Fontconfig] Hinting paths

[Nikolaus Waxweiler]

Hi List,
so I'm currently trying to figure out which hinting paths a glyph can
take from the perspective of fontconfig. So far I found:

TrueType:
- hintslight, autohint true/false: autohinter, fits to Y-axis
- hintmedium, autohint false: ???
- hintmedium, autohint true: autohinter X-and-Y-fitting?
- hintfull, autohint false: native, X-and-Y-fitting or Y-fitting only
depending on the instructions in the font?
- hintfull, autohint true: stronger autohinter X-and-Y-fitting?

OpenType/CFF:
- hintslight, autohint true/false: autohinter, Y-fitting
- hintmedium == hintfull, autohint false: native, Y-fitting only
- hintmedium, autohint true: autohinter X-and-Y-fitting?
- hintfull, autohint true: stronger autohinter X-and-Y-fitting?

Type 1:
- hintslight, autohint true/false: autohinter, Y-fitting
- hintmedium, autohint false: low-quality Y-fitting
- hintmedium, autohint true: autohinter X-and-Y-fitting?
- hintfull, autohint false: slightly thinner low-quality Y-fitting?
- hintfull, autohint true: stronger autohinter X-and-Y-fitting?


So, questions:
- With autohint on, hintslight/medium/full do Y-fitting, X-and-Y-fitting 
and stronger X-and-Y-fitting from within the autohinter *without any 
"native hinting"*? Werner said, the autohinter just does X-and-Y and 
Y-only fitting, so where does the difference between medium and full 
come from?
- With autohint off, what does hintmedium/full do for TrueType and Type1 
fonts? Medium == full for CFF fonts?
- I don't understand FC's source. How does it tell FT what hinting style 
to apply?