Problem calling midi windows api using winapi/winmm for extern

Hi,

I'm new to rust and am just trying to call a windows midi function - I found a nice intro to this at lowmidi.htm

So my code compiles and runs, but I get no names coming back in the structure, while others (in other languages) do here (search cos cannot post links) - how-to-get-midi-device-names

The output of running my code is below, I was hoping that the AAA would be set by the windows function to the names of my midi devices. It correctly notices my midi device when I turn it on/off in the count, but the names do not appear.

Any ideas? Am I making an obvious rookie error? I'm on Windows 10 Home 1909, a pretty vanilla dell build.

C:/Users/dave/.cargo/bin/cargo.exe run --color=always --package playground_r --bin playground_r
   Compiling playground_r v0.1.0 (C:\working\rust\playground_r)
    Finished dev [unoptimized + debuginfo] target(s) in 0.48s
     Running `target\debug\playground_r.exe`
Hello, world!
Got num_midi_in of 1
sz is 76
For 0 got ok of 0 and name of Ok("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA") all is MIDIINCAPSW { wMid: 0, wPid: 0, vDriverVersion: 0, szPname: [65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65], dwSupport: 0 }
Got num_midi_out of 2
sz is 84
For 0 got ok of 0 and name of Ok("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA") all is MIDIOUTCAPSW { wMid: 0, wPid: 0, vDriverVersion: 0, szPname: [65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65], wTechnology: 0, wVoices: 0, wNotes: 0, wChannelMask: 0, dwSupport: 0 }
For 1 got ok of 0 and name of Ok("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA") all is MIDIOUTCAPSW { wMid: 0, wPid: 0, vDriverVersion: 0, szPname: [65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65], wTechnology: 0, wVoices: 0, wNotes: 0, wChannelMask: 0, dwSupport: 0 }

Process finished with exit code 0

using cargo.toml of

[package]
name = "playground_r"
version = "0.1.0"
authors = ["dave"]
edition = "2018"

[dependencies]
winmm-sys = "0.2.0"
winapi = "0.2.8"

and code of

#![allow(dead_code)]
#![allow(non_snake_case)]
extern crate winmm;
extern crate winapi;
use std::mem;
use winapi::mmsystem;

mod tests1;

fn main() {
    println!("Hello, world!");
    check_midi_in();
    check_midi_out();
}

fn check_midi_out() {
    let num_midi = unsafe {
        winmm::midiOutGetNumDevs()
    };
    println!("Got num_midi_out of {}", num_midi);
    let wchar32_space: [u16; 32] = [65; 32];
    #[allow(non_snake_case)]
    let caps = mmsystem::MIDIOUTCAPSW {
        wMid: 0,
        wPid: 0,
        vDriverVersion: 0,
        szPname: wchar32_space,
        wTechnology: 0,
        wVoices: 0,
        wNotes: 0,
        wChannelMask: 0,
        dwSupport: 0,
    };
    let raw_caps = Box::into_raw(Box::new(caps));
    let sz = mem::size_of::<mmsystem::MIDIOUTCAPSW>();
    println!("sz is {}", sz);
    for i in 0..num_midi {
        let id = i as u64;
        let name_ok = unsafe {
            winmm::midiOutGetDevCapsW(id, raw_caps, sz as u32)
        };
        println!("For {} got ok of {} and name of {:?} all is {:?}", id, name_ok, String::from_utf16(&caps.szPname), &caps);
    }
}

fn check_midi_in() {
    let num_midi_in = unsafe {
        winmm::midiInGetNumDevs()
    };
    println!("Got num_midi_in of {}", num_midi_in);
    let wchar32_space: [u16; 32] = [65; 32];
    let caps = mmsystem::MIDIINCAPSW {
        wMid: 0,
        wPid: 0,
        vDriverVersion: 0,
        szPname: wchar32_space,
        dwSupport: 0
    };
    let raw_caps = Box::into_raw(Box::new(caps));
    let sz = mem::size_of::<mmsystem::MIDIINCAPSW>();
    println!("sz is {}", sz);
    for i in 0..num_midi_in {
        let id = i as u64;
        let name_ok = unsafe {
            winmm::midiInGetDevCapsW(id, raw_caps, sz as u32)
        };
        println!("For {} got ok of {} and name of {:?} all is {:?}", id, name_ok, String::from_utf16(&caps.szPname), &caps);
    }
}

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Thanks for the info, I was wondering how I should do that but didn't find that link. Fixed my post.

I fished through the midir library to see why that works and mine doesn't and if I switch to using

[dependencies]
winrt = "0.7.2"
winapi = { version = "0.3.9", features = ["mmsystem", "mmeapi"] }

then everything seems to work. So I'm going to close this.