①BCN_DROPDOWN
Sent when the user clicks a drop down arrow on a button. The parent window of the control receives this notification code in the form of a WM_NOTIFY message
②BCN_HOTITEMCHANGE
Notifies the button control owner that the mouse is entering or leaving the client area of the button control. The button control sends this notification code in the form of a WM_NOTIFY message
③BN_CLICKED
Sent when the user clicks a button
④BN_DBLCLK
Sent when the user double-clicks a button
⑤BN_DISABLE
Sent when a button is disabled
⑥BN_DOUBLECLICKED
Sent when the user double-clicks a button
⑦BN_HILITE
Sent when the user selects a button
⑧BN_KILLFOCUS
Sent when a button loses the keyboard focus
⑨BN_PAINT
Sent when a button should be painted
⑩BN_PUSHED
Sent when the push state of a button is set to pushed
①①BN_SETFOCUS
Sent when a button receives the keyboard focus. The button must have the BS_NOTIFY style to send this notification code
①②BN_UNHILITE
Sent when the highlight should be removed from a button
①③BN_UNPUSHED
Sent when the push state of a button is set to unpushed
①④NM_CUSTOMDRAW
Notifies the parent window of a button control about custom draw operations on the button
【Windows API】Button Control Notifications,布布扣,bubuko.com
【Windows API】Button Control Notifications
原文：http://www.cnblogs.com/Cxx-Code/p/3632072.html