The BN_UNPUSHED notification message is sent when the push state of a button is set to unpushed. The parent window of the button receives this notification message through the WM_COMMAND message.
BN_PUSHED
BN_UNPUSHED is the same as the BN_UNHILITE notification message.
This notification message is provided for compatibility with applications written for versions of Windows earlier than version 3.0. New applications should use the BS_OWNERDRAW button style and the DRAWITEMSTRUCT structure for this task.