LB_GETTOPINDEX
wParam = 0; /* not used, must be zero */
lParam = 0L; /* not used, must be zero */
An application sends an LB_GETTOPINDEX message to retrieve the index of the first visible item in a list box. Initially, the item with index 0 is at the top of the list box, but if the list box is scrolled, another item may be at the top.
This message has no parameters.
The return value is the zero-based index of the first visible item in a list box.