Looks good at smaller sizes.
But it's using up more space (and the body is bigger). Is this OK?

Also, looking at your site - here
https://lh5.googleusercontent.com/-49-d0moPGMw/Tf4xecbJ2yI/AAAAAAAAALA/h...
the character of the font is changing massively at 36.

hhp

I think that most of the autohinter outputted fonts produces slightly more compact text horizontally, i.e. slightly shorter lines.

At some small ppem the autohinted output creates taller x height, or is it the manual hinting creating a shorter x-height?

The first test version of ttfautohint was tending to flatten curves somewhat at certain ppem sizes - a good example is the shot you linked to above. That issue has now been reduced and is still being improved upon. As i understand the problem, GDI has more agressive vertical filtering compared to OSX Quartz or Freetype. GDI agressively switches stray pixels outside snap zones to white and inside zones to black, to give that typical ClearType sharpness at baseline etc. The key will be to tweak the autohinter to output instructions to give a tiny bit less harsh rendering.

>>At some small ppem the autohinted output creates taller x height, or is it the manual hinting creating a shorter x-height?<<

The manual hinting in this case makes things shorter, but it could also make it larger. The point is, the x-height is a decision that a human made. I think that having control over the height zones would be an important option with the autohinter.

Jason

>The key will be to tweak the autohinter to output instructions to give a tiny bit less harsh rendering.

In GDI cleartype, this'd have to be one miraculous tweak my man.

>In GDI cleartype, this'd have to be one miraculous tweak my man.<

Exactly. Likely to be many many lesser tweaks rather than one miraculous tweak.

Also, the goal is not about the emulation of manual hinting. GDI was perfectly suited to needing labour intensive human intervention to give satisfactory font rendering. DirectWrite seems not hungry for it, which makes sense looking at the way the OS is going.

Impressive.