GetWindowTextW

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

INT GetWindowTextW(
    HWND hWnd,
    LPWSTR lpString,
    INT nMaxCount
);

<DllImport("USER32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, ExactSpelling:=True)>
Public Shared Function GetWindowTextW(
    hWnd As IntPtr,   ' HWND
    <MarshalAs(UnmanagedType.LPWStr)> lpString As System.Text.StringBuilder,   ' LPWSTR out
    nMaxCount As Integer   ' INT
) As Integer
End Function

' hWnd : HWND
' lpString : LPWSTR out
' nMaxCount : INT
Declare PtrSafe Function GetWindowTextW Lib "user32" ( _
    ByVal hWnd As LongPtr, _
    ByVal lpString As LongPtr, _
    ByVal nMaxCount As Long) As Long
' 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

GetWindowTextW = ctypes.windll.user32.GetWindowTextW
GetWindowTextW.restype = ctypes.c_int
GetWindowTextW.argtypes = [
    wintypes.HANDLE,  # hWnd : HWND
    wintypes.LPWSTR,  # lpString : LPWSTR out
    ctypes.c_int,  # nMaxCount : INT
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('USER32.dll')
GetWindowTextW = Fiddle::Function.new(
  lib['GetWindowTextW'],
  [
    Fiddle::TYPE_VOIDP,  # hWnd : HWND
    Fiddle::TYPE_VOIDP,  # lpString : LPWSTR out
    Fiddle::TYPE_INT,  # nMaxCount : INT
  ],
  Fiddle::TYPE_INT)
# Wide strings: pass str.encode("UTF-16LE") + "\x00\x00"

#[link(name = "user32")]
extern "system" {
    fn GetWindowTextW(
        hWnd: *mut core::ffi::c_void,  // HWND
        lpString: *mut u16,  // LPWSTR out
        nMaxCount: i32  // INT
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("USER32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
public static extern int GetWindowTextW(IntPtr hWnd, [MarshalAs(UnmanagedType.LPWStr)] System.Text.StringBuilder lpString, int nMaxCount);
"@
$api = Add-Type -MemberDefinition $sig -Name 'USER32_GetWindowTextW' -Namespace Win32 -PassThru
# $api::GetWindowTextW(hWnd, lpString, nMaxCount)

#uselib "USER32.dll"
#func global GetWindowTextW "GetWindowTextW" wptr, wptr, wptr
; GetWindowTextW hWnd, varptr(lpString), nMaxCount   ; 戻り値は stat
; hWnd : HWND -> "wptr"
; lpString : LPWSTR out -> "wptr"
; nMaxCount : INT -> "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 GetWindowTextW "GetWindowTextW" sptr, var, int
; res = GetWindowTextW(hWnd, lpString, nMaxCount)
; hWnd : HWND -> "sptr"
; lpString : LPWSTR out -> "var"
; nMaxCount : INT -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

; INT GetWindowTextW(HWND hWnd, LPWSTR lpString, INT nMaxCount)
#uselib "USER32.dll"
#cfunc global GetWindowTextW "GetWindowTextW" intptr, var, int
; res = GetWindowTextW(hWnd, lpString, nMaxCount)
; hWnd : HWND -> "intptr"
; lpString : LPWSTR out -> "var"
; nMaxCount : INT -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

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

var (
	user32 = windows.NewLazySystemDLL("USER32.dll")
	procGetWindowTextW = user32.NewProc("GetWindowTextW")
)

// hWnd (HWND), lpString (LPWSTR out), nMaxCount (INT)
r1, _, err := procGetWindowTextW.Call(
	uintptr(hWnd),
	uintptr(lpString),
	uintptr(nMaxCount),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // INT

function GetWindowTextW(
  hWnd: THandle;   // HWND
  lpString: PWideChar;   // LPWSTR out
  nMaxCount: Integer   // INT
): Integer; stdcall;
  external 'USER32.dll' name 'GetWindowTextW';

result := DllCall("USER32\GetWindowTextW"
    , "Ptr", hWnd   ; HWND
    , "Ptr", lpString   ; LPWSTR out
    , "Int", nMaxCount   ; INT
    , "Int")   ; return: INT

●GetWindowTextW(hWnd, lpString, nMaxCount) = DLL("USER32.dll", "int GetWindowTextW(void*, char*, int)")
# 呼び出し: GetWindowTextW(hWnd, lpString, nMaxCount)
# hWnd : HWND -> "void*"
# lpString : LPWSTR out -> "char*"
# nMaxCount : INT -> "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。