fix: restore tray icon after Explorer restart

internal/client/windowstray/tray_windows.go

@@ -70,9 +70,11 @@ var (
 	procGetCursorPos      = user32Tray.NewProc("GetCursorPos")
 	procSetForeground     = user32Tray.NewProc("SetForegroundWindow")
 	procGetModuleHandle   = user32Tray.NewProc("GetModuleHandleW")
+	procRegisterMessage   = user32Tray.NewProc("RegisterWindowMessageW")
 	procShellNotify       = shell32Tray.NewProc("Shell_NotifyIconW")
 	trayCallback          = syscall.NewCallback(trayWindowProc)
 	trayWindows           sync.Map // hwnd -> *trayWindow
+	taskbarCreatedMessage uint32
 )
 
 type trayPoint struct{ X, Y int32 }
@@ -212,7 +214,10 @@ func runTrayMessageLoop(output io.Writer, tooltip string, ready chan<- *trayWind
 	window.icon = trayIconData{CbSize: uint32(unsafe.Sizeof(trayIconData{})), HWnd: hwnd, UID: trayIconID, UFlags: trayNIFMessage | trayNIFIcon | trayNIFTip, UCallbackMessage: trayMessage, HIcon: icon}
 	copy(window.icon.Tip[:], winapi.StringToUTF16(tooltip))
 	trayWindows.Store(hwnd, window)
-	if result, _, err := procShellNotify.Call(uintptr(trayNIMAdd), uintptr(unsafe.Pointer(&window.icon))); result == 0 {
+	messageName, _ := winapi.UTF16PtrFromString("TaskbarCreated")
+	registeredMessage, _, _ := procRegisterMessage.Call(uintptr(unsafe.Pointer(messageName)))
+	taskbarCreatedMessage = uint32(registeredMessage)
+	if err := window.addIcon(); err != nil {
 		trayWindows.Delete(hwnd)
 		_, _, _ = procDestroyWindow.Call(hwnd)
 		done <- err
@@ -263,10 +268,28 @@ func trayWindowProc(hwnd uintptr, message uint32, wParam, lParam uintptr) uintpt
 		}
 		return 0
 	}
+	if window != nil && taskbarCreatedMessage != 0 && message == taskbarCreatedMessage {
+		// Explorer may restart without destroying the tray window. Re-add the
+		// icon with the current bounded tooltip so the frontend recovers without
+		// restarting the service or tray process.
+		_ = window.addIcon()
+		return 0
+	}
 	result, _, _ := procDefWindowProc.Call(hwnd, uintptr(message), wParam, lParam)
 	return result
 }
 
+func (window *trayWindow) addIcon() error {
+	window.icon.UFlags = trayNIFMessage | trayNIFIcon | trayNIFTip
+	if result, _, err := procShellNotify.Call(uintptr(trayNIMAdd), uintptr(unsafe.Pointer(&window.icon))); result == 0 {
+		if err == syscall.Errno(0) {
+			err = syscall.GetLastError()
+		}
+		return err
+	}
+	return nil
+}
+
 func (window *trayWindow) removeIcon() {
 	window.closeOnce.Do(func() {
 		window.icon.UFlags = 0
@@ -400,10 +423,10 @@ func (window *trayWindow) setTooltip(value string) {
 }
 
 func openExactPath(path string) error {
-	if path == "" || strings.TrimSpace(path) != path || !utf8.ValidString(path) {
+	if path == "" || strings.TrimSpace(path) != path || !utf8.ValidString(path) || !filepath.IsAbs(path) {
 		return errors.New("invalid path returned by service")
 	}
-	info, err := os.Stat(path)
+	info, err := os.Lstat(path)
 	if err != nil || !info.Mode().IsRegular() {
 		return errors.New("service path is not a regular file")
 	}
@@ -412,7 +435,7 @@ func openExactPath(path string) error {
 		return err
 	}
 	explorer := filepath.Join(windowsDir, "explorer.exe")
-	if info, err := os.Stat(explorer); err != nil || !info.Mode().IsRegular() {
+	if info, err := os.Lstat(explorer); err != nil || !info.Mode().IsRegular() {
 		return errors.New("Windows Explorer is unavailable")
 	}
 	return exec.Command(explorer, path).Start()