The DL_DRAGGING notification message signals that the user has moved the mouse while dragging an item. DL_DRAGGING is also sent periodically during dragging even if the mouse is not moved. A drag list box sends this notification to its parent window in the form of a drag list message.
DL_DRAGGING idCtl = (int) wParam; pDragInfo = (LPDRAGLISTINFO) lParam;
The return value determines the type of mouse cursor that the drag list should set; it can be the DL_STOPCURSOR, DL_COPYCURSOR, or DL_MOVECURSOR value. If any other value is returned, the cursor does not change.
A window procedure typically processes the DL_DRAGGING notification message by determining the item under the cursor and then drawing an insert icon. To get the item under the cursor, use the LBItemFromPt function, specifying TRUE for the bAutoScroll parameter. This option causes the drag list box to scroll periodically if the cursor is above or below its client area. To draw the insert icon, use the DrawInsert function.