BCGCBPRODLLEXPORT UINT BCGM_ON_DRAW_SCROLLBAR

The framework sends BCGM_ON_DRAW_SCROLLBAR registered message to the scroll bar's owner when the scroll bar's style is set to BCGP_SBSTYLE_OWNER_DRAW.

Parameters

wParam	control ID of scroll bar.
lParam	a pointer to BCGPSCROLLBAR_DRAW_INFO structure.

Returns

the return value is ignored.

You should process this message to implement owner draw scrollbars.