NIN_BALLOONHIDE top-level constant Null safety
Sent when the balloon disappears. For example, when the icon is deleted. This message is not sent if the balloon is dismissed because of a timeout or if the user clicks the mouse. As of Windows 7, NIN_BALLOONHIDE is also sent when a notification with the NIIF_RESPECT_QUIET_TIME flag set attempts to display during quiet time (a user's first hour on a new computer). In that case, the balloon is never displayed at all.
const NIN_BALLOONHIDE = WM_USER + 3;