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<H1>form_fieldtype 3x</H1>
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<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
<STRONG><A HREF="form_fieldtype.3x.html">form_fieldtype(3x)</A></STRONG>                                   <STRONG><A HREF="form_fieldtype.3x.html">form_fieldtype(3x)</A></STRONG>


</PRE>
<H2>NAME</H2><PRE>
       <STRONG>form_fieldtype</STRONG> - define validation-field types


</PRE>
<H2>SYNOPSIS</H2><PRE>
       <STRONG>#include</STRONG> <STRONG>&lt;form.h&gt;</STRONG>
       FIELDTYPE *new_fieldtype(
           bool (* const field_check)(FIELD *, const void *),
           bool (* const char_check)(int, const void *));
       int free_fieldtype(FIELDTYPE *fieldtype);
       int set_fieldtype_arg(
           FIELDTYPE *fieldtype,
           void *(* const make_arg)(va_list *),
           void *(* const copy_arg)(const void *),
           void  (* const free_arg)(void *));
       int set_fieldtype_choice(
           FIELDTYPE *fieldtype,
           bool (* const next_choice)(FIELD *, const void *),
           bool (* const prev_choice)(FIELD *, const void *));
       FIELDTYPE *link_fieldtype(FIELDTYPE *type1,
                                 FIELDTYPE *type2);


</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 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 <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_arg</STRONG> associates  three  storage-
       management  functions  with  a  field  type.  The <EM>make</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  argu-
       ment-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 <EM>make</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>make</EM><STRONG>_</STRONG><EM>arg</EM> does not allocate
       memory  but simply loads the argument into a single scalar
       value.

       The function <STRONG>link_fieldtype</STRONG> creates a new field type  from
       the  two  given  types.   They are connected by an logical
       'OR'.

       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
       predecessor functions for the field type.  These functions
       take the field pointer and an argument-block structure  as
       arguments.


</PRE>
<H2>RETURN VALUE</H2><PRE>
       The  pointer-valued  routines  return NULL on error.  They
       set errno according to their success:

       <STRONG>E_OK</STRONG> The routine succeeded.

       <STRONG>E_BAD_ARGUMENT</STRONG>
            Routine detected an incorrect or  out-of-range  argu-
            ment.

       <STRONG>E_SYSTEM_ERROR</STRONG>
            System error occurred, e.g., malloc failure.

       The  integer-valued  routines  return one of the following
       codes on error:

       <STRONG>E_OK</STRONG> The routine succeeded.

       <STRONG>E_BAD_ARGUMENT</STRONG>
            Routine detected an incorrect or  out-of-range  argu-
            ment.

       <STRONG>E_CONNECTED</STRONG>
            The field is already connected to a form.

       <STRONG>E_CURRENT</STRONG>
            The field is the current field.

       <STRONG>E_SYSTEM_ERROR</STRONG>
            System error occurred (see <STRONG>errno</STRONG>).


</PRE>
<H2>SEE ALSO</H2><PRE>
       <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="form.3x.html">form(3x)</A></STRONG>.


</PRE>
<H2>NOTES</H2><PRE>
       The header file <STRONG>&lt;form.h&gt;</STRONG> automatically includes the header
       file <STRONG>&lt;curses.h&gt;</STRONG>.

       All of the <STRONG>(char</STRONG> <STRONG>*)</STRONG> arguments of  these  functions  should
       actually  be <STRONG>(void</STRONG> <STRONG>*)</STRONG>.  The type has been left uncorrected
       for strict compatibility with System V.


</PRE>
<H2>PORTABILITY</H2><PRE>
       These routines emulate the System V forms  library.   They
       were not supported on Version 7 or BSD versions.


</PRE>
<H2>AUTHORS</H2><PRE>
       Juergen  Pfeifer.   Manual  pages  and  adaptation for new
       curses by Eric S. Raymond.


                                                     <STRONG><A HREF="form_fieldtype.3x.html">form_fieldtype(3x)</A></STRONG>
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