January 1, 2001 FORMS 3

### NAME

free_fieldtype, link_fieldtype, new_fieldtype, set_fieldtype_arg, set_fieldtype_choice - form library

### LIBRARY

Curses Form Library (libform, -lform)

### SYNOPSIS

```int` free_fieldtype(```FIELDTYPE *fieldtype`)
```FIELDTYPE``*` link_fieldtype(```FIELDTYPE *type1``, FIELDTYPE *type2`)
```FIELDTYPE``*` new_fieldtype(`` ```int (*field_check)(FIELD *, char *)` ```int (*char_check)(int, char *)` )
```int` set_fieldtype_arg(`` ```FIELDTYPE *fieldtype` ```char * (*make_args)(va_list *)` ```char * (*copy_args)(char *)` ```void (*free_args)(char *)` )
```int` set_fieldtype_choice(`` ```FIELDTYPE *fieldtype` ```int (*next_choice)(FIELD *, char *)` ```int (*prev_choice)(FIELD *, char *)` )

### DESCRIPTION

The function free_fieldtype(``) frees the storage associated with the field type and destroys it. The function link_fieldtype(``) links together the two given field types to produce a new field type. A new field type can be created by calling new_fieldtype(``) which requires pointers to two functions which perform validation, the ```field_check` function must validate the field contents and return ```TRUE` if they are acceptable and ```FALSE` if they are not. The ```char_check` validates the character input into the field, this function will be called for each character entered, if the character can be entered into the field then ```char_check` must return ```TRUE`. Neither ```field_check` nor ```char_check` may be ```NULL`. The functions for handling the field type arguments can be defined by using the set_fieldtype_arg(``) function, the ```make_args` function is used to create new arguments for the fieldtype, the ```copy_args` is used to copy the fieldtype arguments to a new arguments structure and ```free_args` is used to destroy the fieldtype arguments and release any associated storage, none of these function pointers may be ```NULL`. The field type choice functions can be set by calling set_fieldtype_choice(``), the ```next_choice` and ```prev_choice` specify the next and previous choice functions for the field type. These functions must perform the necessary actions to select the next or previous choice for the field, updating the field buffer if necessary. The choice functions must return ```TRUE` if the function succeeded and ```FALSE` otherwise.

### RETURN VALUES

Functions returning pointers will return ```NULL` if an error is detected. The functions that return an int will return one of the following error values:

```E_OK`
  The function was successful.
```E_BAD_ARGUMENT`
  The function was passed a bad argument.
```E_CONNECTED`
  The field is connected to a form.

### SEE ALSO

curses(3), forms(3)

### NOTES

The header <```form.h`> automatically includes both <```curses.h`> and <```eti.h`>.