Use new CStr constants

[pronebird]

Hi,

If we bump MSRV to Rust 1.77 (Currently at 1.71 based on GH workflow), then I think we could use c"<constant>" syntax to generate &CStr constants, which would trim quite a bit of unsafe code, i.e:

pub const kIOKitBuildVersionKey: &CStr =
    unsafe { CStr::from_bytes_with_nul_unchecked(b"IOKitBuildVersion\0") };

would become:

pub const kIOKitBuildVersionKey: &CStr = c"IOKitBuildVersion";

[madsmtm]

Yeah, I'm aware. I've held off on it for now, since it isn't clear what our MSRV policy needs to be, though I know that a lot of projects have very low MSRV, and I'd rather not have that affect adoption.

But definitely something to do in the future.

[merlinaudio]

Does this affect the AX constants too? Like kAXFocusedWindowChangedNotification? I noticed those are missing from objc2_application_services

[madsmtm]

No, that's defined as:

#define kAXFocusedWindowChangedNotification		CFSTR("AXFocusedWindowChanged")

To handle this, we'd need to emit it as:

static kAXFocusedWindowChangedNotification: &CFString = cf_string!("AXFocusedWindowChanged");

But the current cf_string! macro (actually only exposed as objc2_foundation::ns_string!, but the implementation would be the same) is conservatively not enabling true static strings, as that requires better integration with the Rust compiler. This is tracked in #258.

In the meantime, you could define a wrapper yourself, something like:

fn kAXFocusedWindowChangedNotification() -> CFRetained<CFString> {
    CFString::from_str("AXFocusedWindowChanged")
}