An application sends an LB_GETHORIZONTALEXTENT message to retrieve from a list box the width, in pixels, by which the list box can be scrolled horizontally (the scrollable width) if the list box has a horizontal scroll bar.
LB_GETHORIZONTALEXTENT
wParam = 0; // not used; must be zero
lParam = 0; // not used; must be zero
This message has no parameters.
The return value is the scrollable width, in pixels, of the list box.
To respond to the LB_GETHORIZONTALEXTENT message, the list box must have been defined with the WS_HSCROLL style.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
List Boxes Overview, List Box Messages, LB_SETHORIZONTALEXTENT