The function new_fieldtype creates a new field type usable for data
validation. You supply it with field_check, a predicate to check the
validity of an entered data string whenever the user attempts to leave a field.
The (FIELD *) argument is passed in so the validation predicate can see the
field's buffer, sizes and other attributes; the second argument is an
argument-block structure, about which more below.
You also supply new_fieldtype with char_check,
a function to validate input characters as they are entered; it will be passed
the character to be checked and a pointer to an argument-block structure.
The function free_fieldtype frees the space allocated for a given
validation type.
The function set_fieldtype_arg associates three storage-management functions
with a field type.
The make_arg function is automatically applied to the
list of arguments you give set_field_type when attaching validation
to a field; its job is to bundle these into an allocated argument-block
object which can later be passed to validation predicated.
The other two hook arguments should copy and free argument-block structures.
They will be used by the forms-driver code.
You must supply the make_arg function,
the other two are optional, you may supply NULL for them.
In this case it is assumed
that make_arg does not allocate memory but simply loads the
argument into a single scalar value.
The function link_fieldtype creates
a new field type from the two given types.
They are connected by an logical 'OR'.
The form driver requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE assume
that the possible values of a field form an ordered set, and provide the forms
user with a way to move through the set.
The set_fieldtype_choice
function allows forms programmers to define successor and predecessor functions
for the field type.
These functions take the field pointer and an
argument-block structure as arguments.
RETURN VALUE
The pointer-valued routines return NULL on error.
They set errno according to their success:
E_OK
The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_SYSTEM_ERROR
System error occurred, e.g., malloc failure.
The integer-valued routines return one of the following codes on
error:
E_OK
The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
The header file <form.h> automatically includes the header file
<curses.h>.
All of the (char *) arguments of these functions should actually be
(void *). The type has been left uncorrected for strict compatibility
with System V.
PORTABILITY
These routines emulate the System V forms library. They were not supported on
Version 7 or BSD versions.
AUTHORS
Juergen Pfeifer. Manual pages and adaptation for new curses by Eric
S. Raymond.