CB_INITSTORAGE (Compact 2013)
This message is sent by an application before adding a large number of items to the list box portion of a combo box. This message allocates memory for storing list box items.
The CB_INITSTORAGE message helps speed up the initialization of combo boxes that have a large number of items (over 100). It reserves the specified amount of memory so that subsequent CB_ADDSTRING and CB_INSERTSTRING messages take the shortest possible time. You can use estimates for the cItems and cb parameters. If you overestimate, the extra memory is allocated, if you underestimate, the normal allocation is used for items that exceed the requested amount.