How to generate headers for third party crate?

[videni]

Here is a rust example to illustrate the problem

my current crate

use crate::canvas::Canvas;
// app_surface is third party crate
pub use app_surface::{AppSurface, IOSViewObj};

#[no_mangle]
pub extern "C" fn create_canvas(ios_obj: IOSViewObj) -> *mut libc::c_void {
    println!(
        "create_canvas, maximum frames: {}",
        ios_obj.maximum_frames
    );
    
    let obj = Canvas::new(AppSurface::new(ios_obj), 0_i32);
    
    let box_obj = Box::new(obj);
    // 将 box_obj 对象的内存管理权转交给调用方
    Box::into_raw(box_obj) as *mut libc::c_void
}

third party crate

#[repr(C)]
pub struct IOSViewObj {
    pub view: *mut Object,
    pub metal_layer: *mut c_void,
    pub maximum_frames: i32,
    pub callback_to_swift: extern "C" fn(arg: i32),
}

No header found for IOSViewObj, got warning:

WARN: Can't find IOSViewObj. This usually means that this type was incompatible or not found.

[crazyboycjr]

Maybe you need to take a look at [parse] and potentially [parse.expand].