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)
    }
}