This question was definitively answered in: "Body text point sizes: whole increments or in between?"

Ok, DB: found it, I guess: http://imap.typophile.com/node/91087 If you are refering to your usual cryptic mode, I’m not getting smarter. There is nothing, as far as I can tell, that relates to my question in that post of yours. I am not asking about delta hints, I am asking about links: my hyphen jumps from one to two pixels and back again at random, seemingly disregarding the control value table. It is not a case of CVT cut-in (Fontlab equivalent) neither.

Sure I’ve made a mistake :) I’m just trying to figure out what. If I size something to a fractional pixel size it goes crazy in Windows. Any idea what it might be?

I’ve read arguments against PPEM specific delta hints (in Fontlab?), claiming they don’t work for fractional sizes. I think from Beat, but I don’t remember. Maybe I was wrong.

Are you considering my workflow now, or are you talking about an ideal VTT world?

I mean px size in CSS.

FF>"I mean px size in CSS."

You mean fractional px sizes in CSS?

I see documentation for spaces but not type sizes. But... I'm fairly certain that if the web designer can and does specify fractional px sizes for fonts, that all instructions should turn off.

Does your instructed hyphen behave "normally", i.e. jump from 1 to 2 to 3 pixels thick smoothly at whole point sizes?

Yes, I am thinking of your process.

I don’t know the exact sizes. These are steps on a slider, and my Firebug plugin returns a full pixel size, which I’m pretty sure it’s not. The hyphen differs from the other letters in that it only uses a double link.

I did generate these files with Fontsquirrel’s generator. It has an option of auto adding hyphens. I’ve double checked that it was turned off, so I don’t think that’s it neither. It would also be wierd for it to override the hyphen that is already in the font.

Let's see a screenshot of the FL y direction hints for the hyphen glyph, including the program.

So, I’ve modified the slider to round all sizes to a full pixel, but that didn’t help. In the end I tested raw files (thanks Karsten), and also a different font (both raw and Fontsquirrel-generated) and it turns out the problem lies with Fontsquirrel.

I’m not exactly sure what it is though. For example, my accented a’s all render differently than their base glyph.

(It should be mentioned they have a y-direction double link to control the distance to diacritica. The base glyph a is locked to alignment zones, but none of the diacritis are.)

Is Fontsquirrel dumping your hints and applying its own autohinting?

I find that you can choose between "use FontSquirrel's Truetype Hinting" and "Keep Existing Hinting" when you choose the expert mode.

Could this be the problem?

(track)

Update: It was an issue with the Fontsquirrel generator, and it also affected composite glyphs. Fixed now.