When wpCnrInsertObject puts an object into a container window, its adds a USAGE_RECORD item to the object's in-use list. Conversely, when wpCnrRemoveObject is called, the USAGE_RECORD item is deleted from the object's in-use list and the object is removed from the container. The following figure shows the syntax of the RECORDITEM data structure:

typedef struct _RECORDITEM
{
  HWND   hwndCnr;            /* Container into which object      */
                             /* is being inserted                */
  PMINIRECORDCORE pRecord;   /* Record pointer within container  */
  ULONG  ulUser;             /* For application use              */
}RECORDITEM;

Likewise, when wpFreeMem is called to free memory, it calls wpDeleteFromObjUseList to delete a USAGE_MEMORY item from the object's in-use list.

When views are closed by the object's wpClose, wpDeleteFromObjUseList removes the applicable USAGE_OPENVIEW item from the object's in-use list. The wpCnrDeleteUseItem method deletes the USAGE_RECORD use-item for the specified container, but does not remove the object from the container. Use wpCnrRemoveObject to delete the USAGE_RECORD use-item and also to remove the object from the container.