Function create_window_class 

pub fn create_window_class(
    name: &Vec<u16>,
    window_procedure: WNDPROC,
) -> (WNDCLASSW, HINSTANCE)

Create WNDCLASSW and handle to it with custom name and WNDPROC.

window_procedure - A callback function, which you define in your application, that processes messages sent to a window.

Read more:

WNDCLASSW - https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-wndclassw

WNDPROC - https://learn.microsoft.com/en-us/windows/win32/api/winuser/nc-winuser-wndproc

Example:

fn main() {
    let class_name = wide_null("My app window Class");
    let window_name = wide_null("My app window");
    let (window_class, h_instance) = create_window_class(&class_name, window_procedure);
    let window_handle = create_window_handle(&window_class, &class_name, &window_name, h_instance);
    create_window(window_handle);
}

Procedure example:

pub unsafe extern "system" fn window_procedure(hwnd: HWND, msg: UINT, w_param: WPARAM, l_param: LPARAM,) -> LRESULT {
   match msg {
       WM_NCCREATE => {
           println!("NC Create");
           let createstruct: *mut CREATESTRUCTW = l_param as *mut _;
           if createstruct.is_null() {
               return 0;
           }
           let boxed_i32_ptr = (*createstruct).lpCreateParams;
           SetWindowLongPtrW(hwnd, GWLP_USERDATA, boxed_i32_ptr as LONG_PTR);
           return 1;
       }
       WM_CREATE => println!("WM Create"),
       WM_CLOSE => drop(DestroyWindow(hwnd)),
       WM_DESTROY => {
           let ptr = GetWindowLongPtrW(hwnd, GWLP_USERDATA) as *mut i32;
           drop(Box::from_raw(ptr));
           println!("Cleaned up the box.");
           PostQuitMessage(0);
       }
       WM_ERASEBKGND => return 1,
       WM_PAINT => your_paint_func(hwnd),
       _ => return DefWindowProcW(hwnd, msg, w_param, l_param),
   }

   0
 }