"lava triangle" => F2

main.go

package main

// #include "stdafx.h"
// #include "Windows.h"

// int _tmain(int argc, _TCHAR* argv[])
// {
//     HWND hwndWindowTarget;
//     HWND hwndWindowNotepad = FindWindow(NULL, L"Untitled - Notepad");
//     if (hwndWindowNotepad)
//     {
//         // Find the target Edit window within Notepad.
//         hwndWindowTarget = FindWindowEx(hwndWindowNotepad, NULL, L"Edit", NULL);
//         if (hwndWindowTarget)
//         {
//             PostMessage(hwndWindowTarget, WM_CHAR, 'G', 0);
//         }
//     }

//     return 0;
// }

import (
	"fmt"
	"log"
	"syscall"
	"unsafe"

	"github.com/lxn/win"
)

var (
	user32             = syscall.MustLoadDLL("user32.dll")
	procEnumWindows    = user32.MustFindProc("EnumWindows")
	procGetWindowTextW = user32.MustFindProc("GetWindowTextW")
)

func EnumWindows(enumFunc uintptr, lparam uintptr) (err error) {
	r1, _, e1 := syscall.Syscall(procEnumWindows.Addr(), 2, uintptr(enumFunc), uintptr(lparam), 0)
	if r1 == 0 {
		if e1 != 0 {
			err = error(e1)
		} else {
			err = syscall.EINVAL
		}
	}
	return
}

func GetWindowText(hwnd syscall.Handle, str *uint16, maxCount int32) (len int32, err error) {
	r0, _, e1 := syscall.Syscall(procGetWindowTextW.Addr(), 3, uintptr(hwnd), uintptr(unsafe.Pointer(str)), uintptr(maxCount))
	len = int32(r0)
	if len == 0 {
		if e1 != 0 {
			err = error(e1)
		} else {
			err = syscall.EINVAL
		}
	}
	return
}

func FindWindow(title string) (syscall.Handle, error) {
	var hwnd syscall.Handle
	cb := syscall.NewCallback(func(h syscall.Handle, p uintptr) uintptr {
		b := make([]uint16, 200)
		_, err := GetWindowText(h, &b[0], int32(len(b)))
		if err != nil {
			// ignore the error
			return 1 // continue enumeration
		}
		if syscall.UTF16ToString(b) == title {
			// note the window
			hwnd = h
			return 0 // stop enumeration
		}
		return 1 // continue enumeration
	})
	EnumWindows(cb, 0)
	if hwnd == 0 {
		return 0, fmt.Errorf("No window with title '%s' found", title)
	}
	return hwnd, nil
}

func main() {
	const title = "lava triangle"
	hWnd, err := FindWindow(title)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Found '%s' window: handle=0x%x\n", title, hWnd)

	win.PostMessage(win.HWND(hWnd), win.WM_CHAR, win.VK_F2, 0)
}