L_BN_UPDATE

When received, this message indicates that L_BITMAPCLASS window will display an altered image.

The L_BITMAPCLASS window's parent receives this code through a WM_COMMAND message from the L_BITMAPCLASS window. Notification occurs before the altered image is displayed.

Parameter	Description
wParam	Contains the wParam parameter of the WM_COMMAND message, and specifies the child-window ID.
lParam	Contains the L_BITMAPCLASS window handle in its low-order word and the L_BN_UPDATE code in its high-order word.