Specifies a scroll-bar code that indicates the user's scrolling request. This parameter can be one of the following:
SB_BOTTOM Scroll to bottom.
SB_ENDSCROLL End scroll.
SB_LINEDOWN Scroll one line down.
SB_LINEUP Scroll one line up.
SB_PAGEDOWN Scroll one page down.
SB_PAGEUP Scroll one page up.
SB_THUMBPOSITION Scroll to the absolute position. The current position is provided in nPos.
SB_THUMBTRACK Drag scroll box to specified position. The current position is provided in nPos.
SB_TOP Scroll to top.
Contains the current scroll-box position if the scroll-bar code is SB_THUMBPOSITION or SB_THUMBTRACK; otherwise not used. Depending on the initial scroll range, nPos may be negative and should be cast to an int if necessary.
If the scroll message came from a scroll-bar control, contains a pointer to the control. If the user clicked a window's scroll bar, this parameter is NULL. The pointer may be temporary and should not be stored for later use.
OnVScroll typically is used by applications that give some feedback while the scroll box is being dragged.
If OnVScroll scrolls the contents of the CWnd object, it must also reset the position of the scroll box with the SetScrollPos member function.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.