INFO: 32-Bit Scroll Ranges

SUMMARY

You can use 32-bit scroll ranges by calling GetScrollPos(); however, you cannot get 32-bit positions for notifications sent while thumb tracking, that is, via the SB_THUMBPOSITION message. This is because thumb position information is not queryable via an application programming interface (API). You only can obtain the 32-bit scroll information only before or after the scroll has taken place.

The scroll bar APIs allow setting a scroll range up to 0x7FFFFFFF via SetScrollRange(), and setting a scroll position within that range using SetScrollPos(). If the WM_HSCROLL or WM_VSCROLL message is processed, the information returned for scroll bar position, nPos, is only a 16-bit value. To obtain the 32-bit information, the GetScrollPos() API must be used.