Taffy 0.8 - taffy values cannot be sent between threads due to *const ()

[PPakalns]

taffy version

0.8

Platform

Rust

What you did

Upgraded taffy to 0.8

What went wrong

Taffy values cannot be sent between threads safely because of *const () .

This limits the usability of taffy in multi threaded use cases where UI may be constructed from multiple threads.

Additional information

Probably due to tagged_ptr in CompactLengthInner.

[nicoburns]

I'm assuming you only need Send and not Sync here? We can probably just unsafe impl that I think (esp. as Taffy itself is single-threaded currently). But eventually I think we may end up needing to make everything generic over a Calc type.

[PPakalns]

I think so.

I'm assuming you only need Send and not Sync here? We can probably just unsafe impl that I think (esp. as Taffy itself is single-threaded currently). But eventually I think we may end up needing to make everything generic over a Calc type.

Would be nice if test would be added that checks if taffy::Style, Tree, etc. supports Sync/Send. To avoid future problems :)

[nicoburns]

I think fixing this properly (without introducing unsoundness) probably does require being generic over the Calc type. Hopefully this won't be too painful.