-</PRE>
-<H2>DESCRIPTION</H2><PRE>
- The function <STRONG>new_fieldtype</STRONG> creates a new field type usable
- for data validation. You supply it with <EM>field</EM><STRONG>_</STRONG><EM>check</EM>, a
- predicate to check the validity of an entered data string
- whenever the user attempt 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 <STRONG>new_fieldtype</STRONG> with <EM>char</EM><STRONG>_</STRONG><EM>check</EM>, 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 <STRONG>free_fieldtype</STRONG> frees the space allocated for
- a given validation type.
-
- The function <STRONG>set_fieldtype</STRONG> associates three storage-man-
- agement functions with a field type. The <EM>mak</EM><STRONG>_</STRONG><EM>arg</EM> function
- is automatically applied to the list of arguments you give
- <STRONG>set_field_type</STRONG> 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 argu-
- ment-block structures. They will be used by the forms-
- driver code. You must supply the <EM>mak</EM><STRONG>_</STRONG><EM>arg</EM> function, the
- other two are optional, you may supply NULL for them. In
- this case it is assumed, that <EM>mak</EM><STRONG>_</STRONG><EM>arg</EM> doesn't allocate
- memory but simply loads the argument into a single scalar
- value.
-
- The form driver requests <STRONG>REQ_NEXT_CHOICE</STRONG> and
- <STRONG>REQ_PREV_CHOICE</STRONG> 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 <STRONG>set_fieldtype_choice</STRONG> func-
- tion allows forms programmers to define successor and pre-
- decessor functions for the field type. These functions
- take the field pointer and an argument-block structure as
- arguments.
+ <STRONG>int</STRONG> <STRONG>set_fieldtype_arg(</STRONG>
+ <STRONG>FIELDTYPE</STRONG> <STRONG>*</STRONG><EM>fieldtype</EM><STRONG>,</STRONG>
+ <STRONG>void</STRONG> <STRONG>*(*</STRONG> <STRONG>const</STRONG> <EM>make</EM><STRONG>_</STRONG><EM>arg</EM><STRONG>)(va_list</STRONG> <STRONG>*),</STRONG>
+ <STRONG>void</STRONG> <STRONG>*(*</STRONG> <STRONG>const</STRONG> <EM>copy</EM><STRONG>_</STRONG><EM>arg</EM><STRONG>)(const</STRONG> <STRONG>void</STRONG> <STRONG>*),</STRONG>
+ <STRONG>void</STRONG> <STRONG>(*</STRONG> <STRONG>const</STRONG> <EM>free</EM><STRONG>_</STRONG><EM>arg</EM><STRONG>)(void</STRONG> <STRONG>*));</STRONG>
+ <STRONG>int</STRONG> <STRONG>set_fieldtype_choice(</STRONG>
+ <STRONG>FIELDTYPE</STRONG> <STRONG>*</STRONG><EM>fieldtype</EM><STRONG>,</STRONG>
+ <STRONG>bool</STRONG> <STRONG>(*</STRONG> <STRONG>const</STRONG> <EM>next</EM><STRONG>_</STRONG><EM>choice</EM><STRONG>)(FIELD</STRONG> <STRONG>*,</STRONG> <STRONG>const</STRONG> <STRONG>void</STRONG> <STRONG>*),</STRONG>
+ <STRONG>bool</STRONG> <STRONG>(*</STRONG> <STRONG>const</STRONG> <EM>prev</EM><STRONG>_</STRONG><EM>choice</EM><STRONG>)(FIELD</STRONG> <STRONG>*,</STRONG> <STRONG>const</STRONG> <STRONG>void</STRONG> <STRONG>*));</STRONG>