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form_fieldtype - define validation-field types |
#include <form.h> |
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 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 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 associates three storage-management functions with a field type. The mak_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 mak_arg function, the other two are optional, you may supply NULL for them. In this case it is assumed, that mak_arg doesn’t 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 pointer-valued routines return NULL on error. The integer-valued routines return one of the following codes on error: |
E_OK |
The routine succeeded. |
E_SYSTEM_ERROR |
System error occurred (see errno). |
E_BAD_ARGUMENT |
Routine detected an incorrect or out-of-range argument. |
E_CONNECTED |
The field is already connected to a form. |
curses(3X), form(3X). |
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 supported on Version 7 or BSD versions. |
Juergen Pfeifer. Manual pages and adaptation for new curses by Eric S. Raymond. |