clip-sync/internal/notify/notify_windows.go

//go:build windows

package notify

import (
	"fmt"
	"sync"
	"syscall"
	"unsafe"
)

// notifier shows balloon notifications via Shell_NotifyIconW. This is a
// self-contained approach (no Start Menu shortcut or AppID registration
// required), unlike WinRT toast notifications. The balloon appears in the
// notification area and a small tray icon is kept for the daemon's lifetime.
type notifier struct{}

// New returns a Windows notifier using Shell_NotifyIcon balloon tips.
func New() Notifier { return notifier{} }

const (
	nifInfo   = 0x00000010
	nimAdd    = 0x00000000
	nimModify = 0x00000001
	niiInfo   = 0x00000001
)

// hwndMessage is the HWND_MESSAGE (-3) pseudo-handle for a message-only window.
const hwndMessage = ^uintptr(2)

var (
	kernel32 = syscall.NewLazyDLL("kernel32.dll")
	user32   = syscall.NewLazyDLL("user32.dll")
	shell32  = syscall.NewLazyDLL("shell32.dll")

	procGetModuleHandleW = kernel32.NewProc("GetModuleHandleW")
	procRegisterClassExW = user32.NewProc("RegisterClassExW")
	procCreateWindowExW  = user32.NewProc("CreateWindowExW")
	procDefWindowProcW   = user32.NewProc("DefWindowProcW")
	procShellNotifyIconW = shell32.NewProc("Shell_NotifyIconW")
)

type wndClassExW struct {
	cbSize        uint32
	style         uint32
	lpfnWndProc   uintptr
	cbClsExtra    int32
	cbWndExtra    int32
	hInstance     uintptr
	hIcon         uintptr
	hCursor       uintptr
	hbrBackground uintptr
	lpszMenuName  *uint16
	lpszClassName *uint16
	hIconSm       uintptr
}

type notifyIconDataW struct {
	cbSize           uint32
	hWnd             uintptr
	uID              uint32
	uFlags           uint32
	uCallbackMessage uint32
	hIcon            uintptr
	szTip            [128]uint16
	dwState          uint32
	dwStateMask      uint32
	szInfo           [256]uint16
	uTimeout         uint32
	szInfoTitle      [64]uint16
	dwInfoFlags      uint32
	guidItem         [16]byte
	hBalloonIcon     uintptr
}

var (
	notifyOnce sync.Once
	notifyHwnd uintptr
	notifyErr  error

	iconMu    sync.Mutex
	iconAdded bool
)

func setup() {
	hInstance, _, _ := procGetModuleHandleW.Call(0)
	if hInstance == 0 {
		notifyErr = syscall.EINVAL
		return
	}

	className, _ := syscall.UTF16PtrFromString("clip-sync-notify")
	wc := wndClassExW{
		cbSize:        uint32(unsafe.Sizeof(wndClassExW{})),
		lpfnWndProc:   procDefWindowProcW.Addr(),
		hInstance:     hInstance,
		lpszClassName: className,
	}
	// Registration may fail if already registered (e.g. re-run) — that's fine.
	_, _, _ = procRegisterClassExW.Call(uintptr(unsafe.Pointer(&wc)))

	hwnd, _, _ := procCreateWindowExW.Call(
		0,
		uintptr(unsafe.Pointer(className)),
		uintptr(unsafe.Pointer(className)),
		0,
		0, 0, 0, 0,
		hwndMessage,
		0, hInstance, 0,
	)
	notifyHwnd = hwnd
	if hwnd == 0 {
		notifyErr = fmt.Errorf("notify: CreateWindowExW failed")
	}
}

func (notifier) Notify(title, body string) error {
	notifyOnce.Do(setup)
	if notifyErr != nil {
		return notifyErr
	}

	var nid notifyIconDataW
	nid.cbSize = uint32(unsafe.Sizeof(nid))
	nid.hWnd = notifyHwnd
	nid.uID = 1
	nid.uFlags = nifInfo
	nid.uTimeout = 5000
	nid.dwInfoFlags = niiInfo

	if info, err := syscall.UTF16FromString(body); err == nil {
		copy(nid.szInfo[:], info)
	}
	if title16, err := syscall.UTF16FromString(title); err == nil {
		copy(nid.szInfoTitle[:], title16)
	}

	iconMu.Lock()
	defer iconMu.Unlock()

	cmd := uintptr(nimAdd)
	if iconAdded {
		cmd = nimModify
	}
	r, _, _ := procShellNotifyIconW.Call(cmd, uintptr(unsafe.Pointer(&nid)))
	if r != 0 {
		iconAdded = true
		return nil
	}

	// Fall back to the other command on failure (e.g. icon already/not yet present).
	other := uintptr(nimAdd)
	if cmd == nimAdd {
		other = nimModify
	}
	r, _, _ = procShellNotifyIconW.Call(other, uintptr(unsafe.Pointer(&nid)))
	if r != 0 {
		iconAdded = true
		return nil
	}
	return fmt.Errorf("notify: Shell_NotifyIconW failed")
}