Cargo.toml

[dependencies.windows]
version = "0.51"
features = [
    "implement",
    "Win32_Foundation",
]

main.rs

#![allow(non_snake_case)]
use windows::{core::*, Win32::Foundation::*};

#[interface("17f409a1-f79d-45f6-962d-9db106cb7727")]
unsafe trait ICompositor: IUnknown {
    unsafe fn CreateVisual(&self, value: u32, visual: *mut Option<IVisual>) -> HRESULT;
}

#[interface("34e49797-1302-4ad6-8975-dd7c5b286e72")]
unsafe trait IVisual: IUnknown {
    unsafe fn GetValue(&self, value: *mut u32) -> HRESULT;
}

#[implement(ICompositor)]
struct Compositor;

impl ICompositor_Impl for Compositor {
    unsafe fn CreateVisual(&self, value: u32, result: *mut Option<IVisual>) -> HRESULT {
        let visual: IVisual = Visual(value).into();
        *result = Some(visual);
        S_OK
    }
}

#[implement(IVisual)]
struct Visual(u32);

impl IVisual_Impl for Visual {
    unsafe fn GetValue(&self, value: *mut u32) -> HRESULT {
        *value = self.0;
        S_OK
    }
}

fn main() -> Result<()> {
    unsafe {
        let compositor: ICompositor = Compositor.into();

        let mut visual: Option<IVisual> = None;
        compositor.CreateVisual(123, &mut visual).ok()?;

        if let Some(visual) = visual {
            let mut value = 0;
            visual.GetValue(&mut value).ok()?;
            println!("value: {}", value);
        }

        Ok(())
    }
}