Add support for AXValue properties

[tmandry]

Seeking feedback on this approach. AXValue<T> is based on the way AXAttribute<T> works.

I have been using this API and personally am pretty happy with it. Unfortunately the implementation depends on servo/core-foundation-rs#652 which is still awaiting review, so I'm marking this PR as a draft in the meantime.

[oNaiPs]

@eiz are you still maintaining this project?

[eiz]

very slowly :P

it looks like the mentioned pr is merged, so can this proceed? approach looks fine

[tmandry]

Unfortunately it's still blocked on upstream issuing a release (servo/core-foundation-rs#706). I just pinged that PR again.

[oNaiPs]

Hi there @eiz, FYI this just got unblocked :)

Unfortunately it's still blocked on upstream issuing a release (servo/core-foundation-rs#706). I just pinged that PR again.

Also please check my comment re: CGPoint

[eiz]

@oNaiPs the CGPoint comment is resolved ya?

happy to get this in, just needs a rebase + mark ready for review

[tmandry]

I rebased. I'm unsure what crate this should be getting types from now though.

• core-graphics-types 0.1: Compatible with several years worth of releases; many crates surely still depend on the 0.1 line, but not the latest
• core-graphics-types 0.2: Latest version of this crate, released 9 months ago, but may be declared deprecated and superseded by objc2-core-foundation (see Future of this project and discussion about objc2 servo/core-foundation-rs#729)
• objc2-core-foundation 0.3: Released this year. Maybe the future?

I think eventually this crate will want to move to the objc2 crates, but it should probably be done all at once. I have a preference for sticking with the core-graphics-types 0.1 line in the meantime and skipping 0.2 so there's less churn.