Simplify COLR API for transforms

[LaurenzV]

Will make it easier to port code from harfbuzz to rustybuzz. I hope I did the libm thing correctly.

[LaurenzV]

Hmm... yeah some advice on how to deal with the feature thingy would be appreciated. 😄

[RazrFalcon]

I would suggest using no-std-float, just like in tiny-skia.

[RazrFalcon]

I would suggest going the tine-skia route by using a trait.

And then

#[cfg(all(not(feature = "std"), feature = "no-std-float"))]
use crate::NoStdFloat;

where needed.

[RazrFalcon]

You can put the new trait somewhere in lib.rs But it should be pub(crate) this time.

[LaurenzV]

I'll mark this as draft since I also want to test it in rustybuzz first, which might take a while.

[LaurenzV]

Is it okay that when building with no default features and variable-fonts, you must also add no-std-float (or std)? Kinda annoying, but not sure if there is a better way...

[RazrFalcon]

Yes, same with tiny-skia. --no-default-features implies adding --feature libm. No better way to handle this to my knowledge.

[LaurenzV]

Okay, should be good now.