If the lScrollInc parameter value is greater than 0 and the CMA_HORIZONTAL attribute is specified, the container window is scrolled to the right. The container window is scrolled down if the lScrollInc parameter value is greater than 0 and the CMA_VERTICAL attribute is specified. Similarly, the container window is scrolled left and up, respectively, if the lScrollInc parameter value is less than 0 and the same two attributes are specified.

If you want the container window to be scrolled by an amount that is indicated with a key, such as the PgUp, PgDn, Home, and End keys, the application can send a key event to the scroll bar.

If the container window is displaying the split details view, the CM_HORZSCROLLSPLITWINDOW message is used for horizontal scrolling.