CreateMDIWindowW

// USER32.dll  (Unicode / -W)
#include <windows.h>

HWND CreateMDIWindowW(
    LPCWSTR lpClassName,
    LPCWSTR lpWindowName,
    WINDOW_STYLE dwStyle,
    INT X,
    INT Y,
    INT nWidth,
    INT nHeight,
    HWND hWndParent,   // optional
    HINSTANCE hInstance,   // optional
    LPARAM lParam
);

<DllImport("USER32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function CreateMDIWindowW(
    <MarshalAs(UnmanagedType.LPWStr)> lpClassName As String,   ' LPCWSTR
    <MarshalAs(UnmanagedType.LPWStr)> lpWindowName As String,   ' LPCWSTR
    dwStyle As UInteger,   ' WINDOW_STYLE
    X As Integer,   ' INT
    Y As Integer,   ' INT
    nWidth As Integer,   ' INT
    nHeight As Integer,   ' INT
    hWndParent As IntPtr,   ' HWND optional
    hInstance As IntPtr,   ' HINSTANCE optional
    lParam As IntPtr   ' LPARAM
) As IntPtr
End Function

' lpClassName : LPCWSTR
' lpWindowName : LPCWSTR
' dwStyle : WINDOW_STYLE
' X : INT
' Y : INT
' nWidth : INT
' nHeight : INT
' hWndParent : HWND optional
' hInstance : HINSTANCE optional
' lParam : LPARAM
Declare PtrSafe Function CreateMDIWindowW Lib "user32" ( _
    ByVal lpClassName As LongPtr, _
    ByVal lpWindowName As LongPtr, _
    ByVal dwStyle As Long, _
    ByVal X As Long, _
    ByVal Y As Long, _
    ByVal nWidth As Long, _
    ByVal nHeight As Long, _
    ByVal hWndParent As LongPtr, _
    ByVal hInstance As LongPtr, _
    ByVal lParam As LongPtr) As LongPtr
' Unicode(W): 文字列は ByVal As LongPtr とし StrPtr(unicodeStr) を渡す
' VBA7前提(PtrSafe)。32bit Office では LongPtr→Long。Integer=16bit / Long=32bit / LongLong=64bit。

import ctypes
from ctypes import wintypes

CreateMDIWindowW = ctypes.windll.user32.CreateMDIWindowW
CreateMDIWindowW.restype = ctypes.c_void_p
CreateMDIWindowW.argtypes = [
    wintypes.LPCWSTR,  # lpClassName : LPCWSTR
    wintypes.LPCWSTR,  # lpWindowName : LPCWSTR
    wintypes.DWORD,  # dwStyle : WINDOW_STYLE
    ctypes.c_int,  # X : INT
    ctypes.c_int,  # Y : INT
    ctypes.c_int,  # nWidth : INT
    ctypes.c_int,  # nHeight : INT
    wintypes.HANDLE,  # hWndParent : HWND optional
    wintypes.HANDLE,  # hInstance : HINSTANCE optional
    ctypes.c_ssize_t,  # lParam : LPARAM
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('USER32.dll')
CreateMDIWindowW = Fiddle::Function.new(
  lib['CreateMDIWindowW'],
  [
    Fiddle::TYPE_VOIDP,  # lpClassName : LPCWSTR
    Fiddle::TYPE_VOIDP,  # lpWindowName : LPCWSTR
    -Fiddle::TYPE_INT,  # dwStyle : WINDOW_STYLE
    Fiddle::TYPE_INT,  # X : INT
    Fiddle::TYPE_INT,  # Y : INT
    Fiddle::TYPE_INT,  # nWidth : INT
    Fiddle::TYPE_INT,  # nHeight : INT
    Fiddle::TYPE_VOIDP,  # hWndParent : HWND optional
    Fiddle::TYPE_VOIDP,  # hInstance : HINSTANCE optional
    Fiddle::TYPE_INTPTR_T,  # lParam : LPARAM
  ],
  Fiddle::TYPE_VOIDP)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "user32")]
extern "system" {
    fn CreateMDIWindowW(
        lpClassName: *const u16,  // LPCWSTR
        lpWindowName: *const u16,  // LPCWSTR
        dwStyle: u32,  // WINDOW_STYLE
        X: i32,  // INT
        Y: i32,  // INT
        nWidth: i32,  // INT
        nHeight: i32,  // INT
        hWndParent: *mut core::ffi::c_void,  // HWND optional
        hInstance: *mut core::ffi::c_void,  // HINSTANCE optional
        lParam: isize  // LPARAM
    ) -> *mut core::ffi::c_void;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("USER32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern IntPtr CreateMDIWindowW([MarshalAs(UnmanagedType.LPWStr)] string lpClassName, [MarshalAs(UnmanagedType.LPWStr)] string lpWindowName, uint dwStyle, int X, int Y, int nWidth, int nHeight, IntPtr hWndParent, IntPtr hInstance, IntPtr lParam);
"@
$api = Add-Type -MemberDefinition $sig -Name 'USER32_CreateMDIWindowW' -Namespace Win32 -PassThru
# $api::CreateMDIWindowW(lpClassName, lpWindowName, dwStyle, X, Y, nWidth, nHeight, hWndParent, hInstance, lParam)

#uselib "USER32.dll"
#func global CreateMDIWindowW "CreateMDIWindowW" wptr, wptr, wptr, wptr, wptr, wptr, wptr, wptr, wptr, wptr
; CreateMDIWindowW lpClassName, lpWindowName, dwStyle, X, Y, nWidth, nHeight, hWndParent, hInstance, lParam   ; 戻り値は stat
; lpClassName : LPCWSTR -> "wptr"
; lpWindowName : LPCWSTR -> "wptr"
; dwStyle : WINDOW_STYLE -> "wptr"
; X : INT -> "wptr"
; Y : INT -> "wptr"
; nWidth : INT -> "wptr"
; nHeight : INT -> "wptr"
; hWndParent : HWND optional -> "wptr"
; hInstance : HINSTANCE optional -> "wptr"
; lParam : LPARAM -> "wptr"
; ※HSP3.7は #func のため戻り値はシステム変数 stat に格納されます。

#uselib "USER32.dll"
#cfunc global CreateMDIWindowW "CreateMDIWindowW" wstr, wstr, int, int, int, int, int, sptr, sptr, sptr
; res = CreateMDIWindowW(lpClassName, lpWindowName, dwStyle, X, Y, nWidth, nHeight, hWndParent, hInstance, lParam)
; lpClassName : LPCWSTR -> "wstr"
; lpWindowName : LPCWSTR -> "wstr"
; dwStyle : WINDOW_STYLE -> "int"
; X : INT -> "int"
; Y : INT -> "int"
; nWidth : INT -> "int"
; nHeight : INT -> "int"
; hWndParent : HWND optional -> "sptr"
; hInstance : HINSTANCE optional -> "sptr"
; lParam : LPARAM -> "sptr"

; HWND CreateMDIWindowW(LPCWSTR lpClassName, LPCWSTR lpWindowName, WINDOW_STYLE dwStyle, INT X, INT Y, INT nWidth, INT nHeight, HWND hWndParent, HINSTANCE hInstance, LPARAM lParam)
#uselib "USER32.dll"
#cfunc global CreateMDIWindowW "CreateMDIWindowW" wstr, wstr, int, int, int, int, int, intptr, intptr, intptr
; res = CreateMDIWindowW(lpClassName, lpWindowName, dwStyle, X, Y, nWidth, nHeight, hWndParent, hInstance, lParam)
; lpClassName : LPCWSTR -> "wstr"
; lpWindowName : LPCWSTR -> "wstr"
; dwStyle : WINDOW_STYLE -> "int"
; X : INT -> "int"
; Y : INT -> "int"
; nWidth : INT -> "int"
; nHeight : INT -> "int"
; hWndParent : HWND optional -> "intptr"
; hInstance : HINSTANCE optional -> "intptr"
; lParam : LPARAM -> "intptr"

import (
	"golang.org/x/sys/windows"
	"unsafe"
)

var (
	user32 = windows.NewLazySystemDLL("USER32.dll")
	procCreateMDIWindowW = user32.NewProc("CreateMDIWindowW")
)

// lpClassName (LPCWSTR), lpWindowName (LPCWSTR), dwStyle (WINDOW_STYLE), X (INT), Y (INT), nWidth (INT), nHeight (INT), hWndParent (HWND optional), hInstance (HINSTANCE optional), lParam (LPARAM)
r1, _, err := procCreateMDIWindowW.Call(
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpClassName))),
	uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(lpWindowName))),
	uintptr(dwStyle),
	uintptr(X),
	uintptr(Y),
	uintptr(nWidth),
	uintptr(nHeight),
	uintptr(hWndParent),
	uintptr(hInstance),
	uintptr(lParam),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // HWND

function CreateMDIWindowW(
  lpClassName: PWideChar;   // LPCWSTR
  lpWindowName: PWideChar;   // LPCWSTR
  dwStyle: DWORD;   // WINDOW_STYLE
  X: Integer;   // INT
  Y: Integer;   // INT
  nWidth: Integer;   // INT
  nHeight: Integer;   // INT
  hWndParent: THandle;   // HWND optional
  hInstance: THandle;   // HINSTANCE optional
  lParam: NativeInt   // LPARAM
): THandle; stdcall;
  external 'USER32.dll' name 'CreateMDIWindowW';

result := DllCall("USER32\CreateMDIWindowW"
    , "WStr", lpClassName   ; LPCWSTR
    , "WStr", lpWindowName   ; LPCWSTR
    , "UInt", dwStyle   ; WINDOW_STYLE
    , "Int", X   ; INT
    , "Int", Y   ; INT
    , "Int", nWidth   ; INT
    , "Int", nHeight   ; INT
    , "Ptr", hWndParent   ; HWND optional
    , "Ptr", hInstance   ; HINSTANCE optional
    , "Ptr", lParam   ; LPARAM
    , "Ptr")   ; return: HWND

●CreateMDIWindowW(lpClassName, lpWindowName, dwStyle, X, Y, nWidth, nHeight, hWndParent, hInstance, lParam) = DLL("USER32.dll", "void* CreateMDIWindowW(char*, char*, dword, int, int, int, int, void*, void*, int)")
# 呼び出し: CreateMDIWindowW(lpClassName, lpWindowName, dwStyle, X, Y, nWidth, nHeight, hWndParent, hInstance, lParam)
# lpClassName : LPCWSTR -> "char*"
# lpWindowName : LPCWSTR -> "char*"
# dwStyle : WINDOW_STYLE -> "dword"
# X : INT -> "int"
# Y : INT -> "int"
# nWidth : INT -> "int"
# nHeight : INT -> "int"
# hWndParent : HWND optional -> "void*"
# hInstance : HINSTANCE optional -> "void*"
# lParam : LPARAM -> "int"
# なでしこ1は32bit・ANSI(Shift_JIS)。文字列=char*(ANSI)、ポインタ/ハンドル=void*(4byte)。
# ※-W(Unicode)関数。なでしこ1はANSIのため -A 版の利用を推奨。