There is some documentation for the PsychoJS lib at
https://psychopy.github.io/psychojs/
but I think you’ll need to look the source directly to check the units:
https://github.com/psychopy/psychojs
I think currently supported are pix, height, norm. Units are one place where we sort of need to rethink completely, due to the move from controlled lab settings to browsers on wide-ranging devices. But this is where things are a bit of a headache for an app designed originally for calibrated labs.
I suppose we could allow cm but we’d have to trust that the conversion was correct.
I think degrees are out of the question. You don’t know how far the screen is or how big it is. Even if you found a way to calibrate that the range of displays in a browser would mean the stimulus would be either way too big for a phone, or way too small on a large desktop display (actually that’s an issue with all except norm and height I expect)
For the fuzzy text, I don’t know the answer. Maybe need @apitiot for that question. You can see the (pixi) text object getting created here though as a place to start looking:
https://github.com/psychopy/psychojs/blob/becf79b5d6b59a41c0510a640b712f186edc7fda/js/visual/TextStim.js#L265
My guess about the last question (testing scales for visibility) is that it’s beyond the scope of pixi but would be great to hear otherwise. I think pixi is really close to the likes of pyglet and pygame - it provides raw low-level rendering but then you’re on your own. But that’s a pretty uninformed guess.
Jon