Curses Form Library (libform, -lform)
The form
library provides a terminal independent form
system using the curses(3)
library. Before using the form
functions the terminal
must be set up by curses(3)
using the initscr
() function or similar. Programs
using form
functions must be linked with the
curses(3) library
-lcurses
.
The form
library provides facilities for
defining form fields, placing a form on the terminal screen, assign pre and
post change operations and setting the attributes of both the form and its
fields.
The form
library allows any settable attribute or option
of both the form and field objects to be defined such that any new form or
field automatically inherits the value as default. Setting the default value
will not affect any field or form that has already been created but will be
applied to subsequent objects. To set the default attribute or option the set
routine is passed a NULL
pointer in the field or form
parameter when calling the set routine. The current default value can be
retrieved by calling the get routine with a NULL
pointer for the field or form parameter.
Any function returning a string pointer will return NULL
if an error occurs. Functions returning an integer will return one of the
following:
This implementation of the forms library does depart in behavior subtly from the
original AT&T implementation. Some of the more notable departures are:
- field wrapping
- For multi-line fields the data will be wrapped as it is entered, this does
not happen in the AT&T implementation.
- buffer 0
- In this implementation, the contents of buffer 0 are always current
regardless of whether the field has been validated or not.
- circular fields
- In the AT&T implementation fields are circular on a page, that is, a
next field from the last field will go to the first field on the current
page. In this implementation a next field request on the last field of a
page will result in the forms library positioning the cursor on the first
field of the next page. If the field is the last field in the form then
going to the next field will be denied, in the AT&T it would result in
the cursor being placed on the first field of the first page.
- buffer returns
- In this implementation only the data entered by the user in the form field
will be returned, unlike the AT&T library which would return the
contents of the field padded to the size of the field with the pad
character.
- The TAB character
- The handling of the TAB character in fields varies between
implementations. In ncurses attempting to set a field contents with a
string containing a TAB will result in an error and will not allow a TAB
to be entered into a field. The AT&T library statically converts tabs
to the equivalent number of spaces when the field buffer is set but the
form driver will not allow a TAB to be inserted into the field buffer.
This implementation allows TAB when setting the field buffer and also will
allow TAB to be inserted into a field buffer via the form driver and
correctly calculates the cursor position allowing for expansion of the TAB
character.
- set_field_printf
- This function is a NetBSD extension and must not
be used in portable code.
O_REFORMAT
- This field option is a NetBSD extension and must
not be used in portable code.