NodeData and MeasureFunc are not thread-safe

[colepoirier]

What problem does this solve or what need does it fill?

"I am implementing a UI layer in an async framework, and I am unable to pass Stretch around (including using it as a member on the "self" structure) in async code because MeasureFunc is not Send/Sync."

taffy/src/node.rs

Line 21 in 59a8e27

Boxed(Box<dyn Fn(Size<Number>) -> Size<f32>>),

What solution would you like?

"I believe that the change may be as simple as changing the type of Boxed's value to sys::Box<dyn Fn(Size) -> Size> + Send + Sync)"

"This, unfortunately, could be a breaking change since this is a publicly exposed enum, so before jumping in to create a PR, I wanted to see what the opinion would be of attempting this change. I'm new enough to understanding how async works that I am not sure what the likelihood that these functions in most codebase wouldn't already be Send + Sync."

What alternative(s) have you considered?

N/A

Additional context

Migrating from vislyhq/stretch#69.

Because this is a migration of an issue, I am reproducing the original using direct quotations (indicated using "..") from the original issue author @ecton but modifying the url to point to taffy code.

[alice-i-cecile]

Thanks! I think the easiest and best solution to this is actually just to remove MeasureFunc completely, per #101.

[colepoirier]

Thanks! I think the easiest and best solution to this is actually just to remove MeasureFunc completely, per #101.

Great! I guess the pr for that should reference this issue so it closes once it is merged?

[alice-i-cecile]

Yes, exactly.