Before creating the scrolling list, we will need to add some variables for
controlling the list:
- List Handles: GIL refers to scrolling lists via two handles, one of
type GSlistHandle and one of type GSsclistHandle. We add the
variables list_handle and sclist_handle.
- Item Count and Current Item: We will keep track of the number of
items in the list with the integer num_checks, and the current item with
- Check Structures: An array, check, of pointers to CheckType
is maintained. Using pointers simplifies adding to and deleting from the list.