Win32 API MessageBox() in Golang

messagebox.go

import (
	"syscall"
	"unsafe"
)

func newGoWinAPI() GoWinAPI {
	return GoWinAPI{
		winAPI: NewWinAPI(),
	}
}

// Struct with simplified WinAPI bindings
type GoWinAPI struct {
	winAPI WinAPI
}

func (api GoWinAPI) MessageBox(windowTitle string, windowContent string, flags uint) int {
	// For reference on flags see: https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-messageboxw
	return api.winAPI.MessageBoxW(
		0, // NULL hwnd
		windowContent,
		windowTitle,
		flags,
	)
}

func NewWinAPI() WinAPI {
	return WinAPI{
		user32dll: syscall.NewLazyDLL("user32.dll"),
	}
}

// Struct with raw WinAPI bindings
type WinAPI struct {
	user32dll *syscall.LazyDLL
}

// MB_BUTTONS
const MB_OK = 0x0
const MB_OKCANCEL = 0x1
const MB_ABORTRETRYIGNORE = 0x2
const MB_YESNOCANCEL = 0x3
const MB_YESNO = 0x4
const MB_RETRYCANCEL = 0x5
const MB_CANCELTRYCONTINUE = 0x6

// MB_ICONS
const MB_ICONNONE = 0x00
const MB_ICONSTOP = 0x10
const MB_ICONERROR = 0x10
const MB_ICONHAND = 0x10
const MB_ICONQUESTION = 0x20
const MB_ICONEXCLAMATION = 0x30
const MB_ICONWARNING = 0x30
const MB_ICONINFORMATION = 0x40
const MB_ICONASTERISK = 0x40

// MB_DEFBUTTON
const MB_DEFBUTTON1 = 0x000
const MB_DEFBUTTON2 = 0x100
const MB_DEFBUTTON3 = 0x200
const MB_DEFBUTTON4 = 0x300

// MB_MODALITY
const MB_APPLMODAL = 0x0000
const MB_SYSTEMMODAL = 0x1000
const mb_TASKMODAL = 0x2000

func (api WinAPI) MessageBoxW(hwnd uintptr, lpText string, lpCaption string, flags uint) int {
	/* https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-messageboxw
	int MessageBoxW(
		[in, optional] HWND    hWnd,
		[in, optional] LPCWSTR lpText,
		[in, optional] LPCWSTR lpCaption,
		[in]           UINT    uType
	);*/
	response, _, _ := api.user32dll.NewProc("MessageBoxW").Call(
		uintptr(hwnd),
		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(lpText))),
		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(lpCaption))),
		uintptr(flags),
	)

	return int(response)
}

// MessageBoxPlain of Win32 API.
func MessageBoxPlain(title, caption string) int {
	const (
		NULL  = 0
		MB_OK = 0
	)
	return MessageBox(NULL, caption, title, MB_OK)
}