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 predi-
- cate can see the field's buffer, sizes and other attributes; the second
- argument is an argument-block structure, about which more below.
+ validation. Its parameters are function pointers:
+
+ field_check
+ This function checks the validity of an entered data string
+ whenever the user attempts to leave a field. It has two
+ arguments:
+
+ o The (FIELD *) argument is passed in so the validation
+ predicate can see the field's buffer, sizes and other
+ attributes.
- 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.
+ o The second argument is an argument-block structure, about
+ which more below.
- The function free_fieldtype frees the space allocated for a given vali-
- dation type.
+ char_check
+ This function validates input characters as they are entered. The
+ form library passes it the character to be checked and a pointer
+ to an argument-block structure.
+
+
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 predi-
- cated. 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.
+ functions with a field type:
+
+ make_arg
+ This function is automatically applied to the list of arguments
+ you give set_field_type when attaching validation to a field. It
+ stores the arguments in an allocated argument-block object which
+ is used when validating input.
+
+ copy_arg
+ This function may be used by applications to copy argument-blocks.
+ free_arg
+ Frees an argument-block structure.
+
+ You must supply the make_arg function. The other two are optional: you
+ may supply NULL for them. In this case, the form library assumes that
+ make_arg does not allocate memory but simply loads the argument into a
+ single scalar value.
+
+
+
+ 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.
+
+
+
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_field-
- type_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.
-
- The pointer-valued routines return NULL on error. They set errno
+ The pointer-valued routines return NULL on error. They set errno
according to their success:
E_OK The routine succeeded.
@@ -133,25 +166,21 @@
The field is the current field.
E_SYSTEM_ERROR
- System error occurred (see errno).
+ System error occurred (see errno(3)).
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.
-
- These routines emulate the System V forms library. They were not sup-
- ported on Version 7 or BSD versions.
+ These routines emulate the System V forms library. They were not
+ supported on Version 7 or BSD versions.