rust-objc VS rust-block

If you find dealing with the Obj-C bindings a bit daunting (I would), I'd recommend you use the objc crate. That will like you dive into the details of creating and updating Mac windows without having to figure out how to call Objective C from Rust.

There is https://github.com/SSheldon/rust-objc which is abandoned.

On macOS, per-window capture is actually exceedingly easy and officially supported by Apple, either including window shadows or not. I'm not aware of any crate for doing it cross-platform, but the way to do it on macOS is documented all over the Internet and the bindings you need are in the objc and core-graphics crates.

That looks like Objective C, not C. You can call Objective C methods from Rust via the objc crate.

let block = ConcreteBlock::new(move |key: *const c_char, value: xpc_object_t| { unsafe { xpc_retain(value) }; let str_key = unsafe { CStr::from_ptr(key).to_string_lossy().to_string() }; let xpc_object: XPCObject = value.into(); map_refcell .borrow_mut() .insert(str_key, xpc_object.into()); true }); // https://github.com/SSheldon/rust-block#creating-blocks let block = block.copy(); let ok = unsafe { xpc_dictionary_apply(object.as_ptr(), &*block as *const _ as *mut _) };