Go で GUI を表示する(RegisterClassEx/CreateWindowEx/GetMessage)

Go で Win32 を呼び出すコードを書き始めている。
とりあえずウィンドウを表示できたので、後の人のために残しておく。

main.go

package main

import (
	"syscall"
	"unsafe"

	"github.com/blono/win" // Fork of lxn/win see https://qiita.com/manymanyuni/items/c41f5bf0fd141e299336
)

func NewUTF16(s string) *uint16 {
	result, _ := syscall.UTF16PtrFromString(s)

	return result
}

func onMessage(window win.HWND, msg uint32, wParam uintptr, lParam uintptr) uintptr {
	switch msg {
	case win.WM_CLOSE:
		win.DestroyWindow(window)
	case win.WM_DESTROY:
		win.PostQuitMessage(0)
	default:
		return win.DefWindowProc(window, msg, wParam, lParam)
	}

	return 0
}

func main() {
	windowClass := win.WNDCLASSEX{
		LpfnWndProc:    syscall.NewCallback(onMessage),
		HInstance:   win.HINSTANCE(0),
		LpszClassName:  winut.NewUTF16("test"),
	}
	windowClass.CbSize = uint32(unsafe.Sizeof(windowClass))

	win.RegisterClassEx(&windowClass)

	window := win.CreateWindowEx(0, winut.NewUTF16("test"), winut.NewUTF16("test-window"),
		win.WS_OVERLAPPEDWINDOW | win.WS_VISIBLE, 100, 100, 500, 500, win.HWND(0), win.HMENU(0), win.HINSTANCE(0), nil)

	win.ShowWindow(window, win.SWP_SHOWWINDOW)
	win.UpdateWindow(window)

	var msg win.MSG

	for win.GetMessage(&msg, 0, 0, 0) > 0 {
		win.TranslateMessage(&msg)
		win.DispatchMessage(&msg)
	}
}