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[bpt/emacs.git] / doc / misc / forms.texi

\input texinfo			@c -*-texinfo-*-
@c documentation for forms-mode
@c Written by Johan Vromans, and edited by Richard Stallman

@comment %**start of header (This is for running Texinfo on a region.)
@setfilename ../../info/forms
@settitle Forms Mode User's Manual
@syncodeindex vr cp
@syncodeindex fn cp
@syncodeindex ky cp
@iftex
@finalout
@setchapternewpage odd
@end iftex
@c      @smallbook
@comment %**end of header (This is for running Texinfo on a region.)

@copying
This file documents Forms mode, a form-editing major mode for GNU Emacs.

Copyright @copyright{} 1989, 1997, 2001, 2002, 2003, 2004,
2005, 2006, 2007 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover texts being ``A GNU
Manual,'' and with the Back-Cover Texts as in (a) below.  A copy of the
license is included in the section entitled ``GNU Free Documentation
License'' in the Emacs manual.

(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
this GNU Manual, like GNU software.  Copies published by the Free
Software Foundation raise funds for GNU development.''

This document is part of a collection distributed under the GNU Free
Documentation License.  If you want to distribute this document
separately from the collection, you can do so by adding a copy of the
license to the document, as described in section 6 of the license.
@end quotation
@end copying

@dircategory Emacs
@direntry
* Forms: (forms).	Emacs package for editing data bases
			  by filling in forms.
@end direntry

@titlepage
@sp 6
@center @titlefont{Forms Mode User's Manual}
@sp 4
@center Forms-Mode version 2
@sp 1
@center for GNU Emacs 22.1
@sp 1
@center April 2007
@sp 5
@center Johan Vromans
@center @i{jvromans@@squirrel.nl}
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@ifnottex
@node Top
@top Forms Mode

Forms mode is an Emacs major mode for working with simple textual data
bases in a forms-oriented manner.  In Forms mode, the information in
these files is presented in an Emacs window in a user-defined format,
one record at a time.  The user can view records or modify their
contents.

Forms mode is not a simple major mode, but requires two files to do its
job: a control file and a data file.  The data file holds the
actual data to be presented.  The control file describes
how to present it.

@menu
* Forms Example::               An example: editing the password data base.
* Entering and Exiting Forms Mode::
                                How to visit a file in Forms mode.
* Forms Commands::              Special commands to use while in Forms mode.
* Data File Format::            How to format the data file.
* Control File Format::         How to control forms mode.
* Format Description::          How to define the forms layout.
* Modifying Forms Contents::    How to modify.
* Miscellaneous::               Forms mode messages and other remarks.
* Error Messages::              List of error messages forms mode can produce.
* Long Example::                A more complex control file example.
* GNU Free Documentation License:: The license for this documentation.
* Credits::                     Thanks everyone.
* Index::                       Index to this manual.
@end menu
@end ifnottex

@node Forms Example
@chapter Forms Example

Let's illustrate Forms mode with an example.  Suppose you are looking at
the @file{/etc/passwd} file, and the screen looks like this:

@example
====== /etc/passwd ======

User : root   Uid: 0   Gid: 1

Name : Super User

Home : /

Shell: /bin/sh
@end example

As you can see, the familiar fields from the entry for the super user
are all there, but instead of being colon-separated on one single line,
they make up a forms.

The contents of the forms consist of the contents of the fields of the
record (e.g. @samp{root}, @samp{0}, @samp{1}, @samp{Super User})
interspersed with normal text (e.g @samp{User : }, @samp{Uid: }).

If you modify the contents of the fields, Forms mode will analyze your
changes and update the file appropriately.  You cannot modify the
interspersed explanatory text (unless you go to some trouble about it),
because that is marked read-only (@pxref{Text Properties,,, elisp, The
Emacs Lisp Reference Manual}).

The Forms mode control file specifies the relationship between the
format of @file{/etc/passwd} and what appears on the screen in Forms
mode.  @xref{Control File Format}.

@node Entering and Exiting Forms Mode
@chapter Entering and Exiting Forms Mode

@table @kbd
@findex forms-find-file
@item M-x forms-find-file @key{RET} @var{control-file} @key{RET}
Visit a database using Forms mode.  Specify the name of the
@strong{control file}, not the data file!

@findex forms-find-file-other-window
@item M-x forms-find-file-other-window @key{RET} @var{control-file} @key{RET}
Similar, but displays the file in another window.
@end table

The command @code{forms-find-file} evaluates the file
@var{control-file}, and also visits it in Forms mode.  What you see in
its buffer is not the contents of this file, but rather a single record
of the corresponding data file that is visited in its own buffer.  So
there are two buffers involved in Forms mode: the @dfn{forms buffer}
that is initially used to visit the control file and that shows the
records being browsed, and the @dfn{data buffer} that holds the data
file being visited.  The latter buffer is normally not visible.

Initially, the first record is displayed in the forms buffer.
The mode line displays the major mode name @samp{Forms}, followed by the
minor mode @samp{View} if the data base is read-only.  The number of the
current record (@var{n}) and the total number of records in the
file(@var{t}) are shown in the mode line as @samp{@var{n}/@var{t}}.  For
example:

@example
--%%-Emacs: passwd-demo          (Forms View 1/54)----All-------
@end example

If the buffer is not read-only, you may change the buffer to modify the
fields in the record.  When you move to a different record, the contents
of the buffer are parsed using the specifications in
@code{forms-format-list}, and the data file is updated.  If the record
has fields that aren't included in the display, they are not changed.

@vindex forms-mode-hooks
Entering Forms mode runs the normal hook @code{forms-mode-hooks} to
perform user-defined customization.

To save any modified data, you can use @kbd{C-x C-s}
(@code{forms-save-buffer}).  This does not save the forms buffer (which would
be rather useless), but instead saves the buffer visiting the data file.

To terminate Forms mode, you can use @kbd{C-x C-s} (@code{forms-save-buffer})
and then kill the forms buffer.  However, the data buffer will still
remain.  If this is not desired, you have to kill this buffer too.

@node Forms Commands
@chapter Forms Commands

The commands of Forms mode belong to the @kbd{C-c} prefix, with one
exception: @key{TAB}, which moves to the next field.  Forms mode uses
different key maps for normal mode and read-only mode.  In read-only
Forms mode, you can access most of the commands without the @kbd{C-c}
prefix, but you must type ordinary letters instead of control
characters; for example, type @kbd{n} instead of @kbd{C-c C-n}.

If your Emacs has been built with X-toolkit support, Forms mode will
provide its own menu with a number of Forms mode commands.

@table @kbd
@findex forms-next-record
@kindex C-c C-n
@item C-c C-n
Show the next record (@code{forms-next-record}).  With a numeric
argument @var{n}, show the @var{n}th next record.

@findex forms-prev-record
@kindex C-c C-p
@item C-c C-p
Show the previous record (@code{forms-prev-record}).  With a numeric
argument @var{n}, show the @var{n}th previous record.

@findex forms-jump-record
@kindex C-c C-l
@item C-c C-l
Jump to a record by number (@code{forms-jump-record}).   Specify
the record number with a numeric argument.

@findex forms-first-record
@kindex C-c <
@item C-c <
Jump to the first record (@code{forms-first-record}).

@findex forms-last-record
@kindex C-c >
@item C-c >
Jump to the last record (@code{forms-last-record}).  This command also
recalculates the number of records in the data file.

@findex forms-next-field
@kindex TAB
@item @key{TAB}
@kindex C-c TAB
@itemx C-c @key{TAB}
Jump to the next field in the current record (@code{forms-next-field}).
With a numeric argument @var{n}, jump forward @var{n} fields.  If this command
would move past the last field, it wraps around to the first field.

@findex forms-toggle-read-only
@kindex C-c C-q
@item C-c C-q
Toggles read-only mode (@code{forms-toggle-read-only}).  In read-only
Forms mode, you cannot edit the fields; most Forms mode commands can be
accessed without the prefix @kbd{C-c} if you use the normal letter
instead (for example, type @kbd{n} instead of @kbd{C-c C-n}).  In edit
mode, you can edit the fields and thus change the contents of the data
base; you must begin Forms mode commands with @code{C-c}.  Switching
to edit mode is allowed only if you have write access to the data file.

@findex forms-insert-record
@kindex C-c C-o
@item C-c C-o
Create a new record and insert it before the current record
(@code{forms-insert-record}).  It starts out with empty (or default)
contents for its fields; you can then edit the fields.  With a numeric
argument, the new record is created @emph{after} the current one.
See also @code{forms-modified-record-filter} in @ref{Modifying Forms
Contents}.

@findex forms-delete-record
@kindex C-c C-k
@item C-c C-k
Delete the current record (@code{forms-delete-record}).  You are
prompted for confirmation before the record is deleted unless a numeric
argument has been provided.

@findex forms-search-forward
@kindex C-c C-s @var{regexp} @key{RET}
@item C-c C-s @var{regexp} @key{RET}
Search forward for @var{regexp} in all records following this one
(@code{forms-search-forward}).  If found, this record is shown.
If you give an empty argument, the previous regexp is used again.

@findex forms-search-backward
@kindex C-c C-r @var{regexp} @key{RET}
@item C-c C-r @var{regexp} @key{RET}
Search backward for @var{regexp} in all records following this one
(@code{forms-search-backward}).  If found, this record is shown.
If you give an empty argument, the previous regexp is used again.

@ignore
@findex forms-exit
@kindex C-c C-x
@item C-c C-x
Terminate Forms mode processing (@code{forms-exit}).  The data file is
saved if it has been modified.

@findex forms-exit-no-save
@item M-x forms-exit-no-save
Terminates forms mode processing without saving modified data first.
@end ignore

@findex forms-prev-field
@item M-x forms-prev-field
Similar to @code{forms-next-field} but moves backwards.

@findex forms-save-buffer
@item M-x forms-save-buffer
@kindex C-x C-s
@itemx C-x C-s
Forms mode replacement for @code{save-buffer}. When executed in the
forms buffer it will save the contents of the (modified) data buffer
instead. In Forms mode this function will be bound to @kbd{C-x C-s}.

@findex forms-print
@item M-x forms-print
This command can be used to make a formatted print
of the contents of the data file.

@end table

In addition the command @kbd{M-x revert-buffer} is useful in Forms mode
just as in other modes.

@ignore
@vindex forms-forms-scroll
@findex scroll-up
@findex scroll-down
If the variable @code{forms-forms-scrolls} is set to a value other
than @code{nil} (which it is, by default), the Emacs functions
@code{scroll-up} and @code{scroll-down} will perform a
@code{forms-next-record} and @code{forms-prev-record} when in forms
mode.  So you can use your favorite page commands to page through the
data file.

@vindex forms-forms-jump
@findex beginning-of-buffer
@findex end-of-buffer
Likewise, if the variable @code{forms-forms-jump} is not @code{nil}
(which it is, by default), Emacs functions @code{beginning-of-buffer}
and @code{end-of-buffer} will perform @code{forms-first-record} and
@code{forms-last-record} when in forms mode.
@end ignore

The following function key definitions are set up in Forms mode
(whether read-only or not):

@table @kbd
@kindex next
@item next
forms-next-record

@kindex prior
@item prior
forms-prev-record

@kindex begin
@item begin
forms-first-record

@kindex end
@item end
forms-last-record

@kindex S-Tab
@findex forms-prev-field
@item S-Tab
forms-prev-field
@end table

@node Data File Format
@chapter Data File Format

@cindex record
@cindex field
@vindex forms-field-sep
Files for use with Forms mode are very simple---each @dfn{record}
(usually one line) forms the contents of one form.  Each record consists
of a number of @dfn{fields}, which are separated by the value of the
string @code{forms-field-sep}, which is @code{"\t"} (a Tab) by default.

@vindex forms-read-file-filter
@vindex forms-write-file-filter
If the format of the data file is not suitable enough you can define the
filter functions @code{forms-read-file-filter} and
@code{forms-write-file-filter}. @code{forms-read-file-filter} is called
when the data file is read from disk into the data buffer. It operates
on the data buffer, ignoring read-only protections. When the data file
is saved to disk @code{forms-write-file-filter} is called to cancel the
effects of @code{forms-read-file-filter}. After being saved,
@code{forms-read-file-filter} is called again to prepare the data buffer
for further processing.

@cindex pseudo-newline
@vindex forms-multi-line
Fields may contain text which shows up in the forms in multiple lines.
These lines are separated in the field using a ``pseudo-newline''
character which is defined by the value of the string
@code{forms-multi-line}.  Its default value is @code{"\^k"} (a Control-K
character).  If it is
set to @code{nil}, multiple line fields are prohibited.

If the data file does not exist, it is automatically created.

@node Control File Format
@chapter Control File Format

@cindex control file
The Forms mode @dfn{control file} serves two purposes.  First, it names
the data file to use, and defines its format and properties.  Second,
the Emacs buffer it occupies is used by Forms mode to display the forms.

The contents of the control file are evaluated as a Lisp program.  It
should set the following Lisp variables to suitable values:

@table @code
@vindex forms-file
@item forms-file
This variable specifies the name of the data file.  Example:

@example
(setq forms-file "my/data-file")
@end example

If the control file doesn't set @code{forms-file}, Forms mode
reports an error.

@vindex forms-format-list
@item forms-format-list
This variable describes the way the fields of the record are formatted on
the screen.  For details, see @ref{Format Description}.

@vindex forms-number-of-fields
@item forms-number-of-fields
This variable holds the number of fields in each record of the data
file.  Example:

@example
(setq forms-number-of-fields 10)
@end example
@end table

If the control file does not set @code{forms-format-list} a default
format is used.  In this situation, Forms mode will deduce the number of
fields from the data file providing this file exists and
@code{forms-number-of-records} has not been set in the control file.

The control file can optionally set the following additional Forms mode
variables.  Most of them have default values that are good for most
applications.

@table @code
@vindex forms-field-sep
@item forms-field-sep
This variable may be used to designate the string which separates the
fields in the records of the data file.  If not set, it defaults to the
string @code{"\t"} (a Tab character).  Example:

@example
(setq forms-field-sep "\t")
@end example

@vindex forms-read-only
@item forms-read-only
If the value is non-@code{nil}, the data file is treated read-only.  (Forms
mode also treats the data file as read-only if you don't have access to
write it.)  Example:

@example
(set forms-read-only t)
@end example

@vindex forms-multi-line
@item forms-multi-line
This variable specifies the @dfn{pseudo newline} separator that allows
multi-line fields.  This separator goes between the ``lines'' within a
field---thus, the field doesn't really contain multiple lines, but it
appears that way when displayed in Forms mode.  If the value is
@code{nil}, multi-line text fields are prohibited.  The pseudo newline
must not be a character contained in @code{forms-field-sep}.

The default value is @code{"\^k"}, the character Control-K.  Example:

@example
(setq forms-multi-line "\^k")
@end example

@ignore
@vindex forms-forms-scroll
@item forms-forms-scroll
@xref{Forms Mode Commands}, for details.

@vindex forms-forms-jump
@item forms-forms-jump
@xref{Forms Mode Commands}, for details.
@end ignore

@findex forms-read-file-filter
@item forms-read-file-filter
This variable holds the name of a function to be called after the data
file has been read in. This can be used to transform the contents of the
data file into a format more suitable for forms processing.
If it is @code{nil}, no function is called.  For example, to maintain a
gzipped database:

@example
(defun gzip-read-file-filter ()
  (shell-command-on-region (point-min) (point-max)
                           "gzip -d" t t))
(setq forms-read-file-filter 'gzip-read-file-filter)
@end example

@findex forms-write-file-filter
@item forms-write-file-filter
This variable holds the name of a function to be called before writing
out the contents of the data file.
This can be used to undo the effects of @code{forms-read-file-filter}.
If it is @code{nil}, no function is called.  Example:

@example
(defun gzip-write-file-filter ()
  (make-variable-buffer-local 'require-final-newline)
  (setq require-final-newline nil)
  (shell-command-on-region (point-min) (point-max)
                           "gzip" t t))
(setq forms-write-file-filter 'gzip-write-file-filter)
@end example

@findex forms-new-record-filter
@item forms-new-record-filter
This variable holds a function to be called whenever a new record is created
to supply default values for fields.  If it is @code{nil}, no function is
called.
@xref{Modifying Forms Contents}, for details.

@findex forms-modified-record-filter
@item  forms-modified-record-filter
This variable holds a function to be called whenever a record is
modified, just before updating the Forms data file.  If it is
@code{nil}, no function is called.
@xref{Modifying Forms Contents}, for details.

@findex forms-insert-after
@item forms-insert-after
If this variable is not @code{nil}, new records are created @emph{after} the
current record. Also, upon visiting a file, the initial position will be
at the last record instead of the first one.

@findex forms-check-number-of-fields
@item forms-check-number-of-fields
Normally each record is checked to contain the correct number of fields.
Under certain circumstances, this can be undesirable.
If this variable is set to @code{nil}, these checks will be bypassed.
@end table

@node Format Description
@chapter The Format Description

@vindex forms-format-list
  The variable @code{forms-format-list} specifies the format of the data
in the data file, and how to convert the data for display in Forms mode.
Its value must be a list of Forms mode @dfn{formatting elements}, each
of which can be a string, a number, a Lisp list, or a Lisp symbol that
evaluates to one of those.  The formatting elements are processed in the
order they appear in the list.

@table @var
@item string
A string formatting element is inserted in the forms ``as is,'' as text
that the user cannot alter.

@item number
A number element selects a field of the record.  The contents of this
field are inserted in the display at this point.  Field numbers count
starting from 1 (one).

@item list
A formatting element that is a list specifies a function call.  This
function is called every time a record is displayed, and its result,
which must be a string, is inserted in the display text.  The function
should do nothing but returning a string.

@vindex forms-fields
The function you call can access the fields of the record as a list in
the variable
@code{forms-fields}.

@item symbol
A symbol used as a formatting element should evaluate to a string, number,
or list; the value is interpreted as a formatting element, as described
above.
@end table

If a record does not contain the number of fields as specified in
@code{forms-number-of-fields}, a warning message will be printed.  Excess
fields are ignored, missing fields are set to empty.

The control file which displays @file{/etc/passwd} file as demonstrated
in the beginning of this manual might look as follows:

@example
;; @r{This demo visits @file{/etc/passwd}.}

(setq forms-file "/etc/passwd")
(setq forms-number-of-fields 7)
(setq forms-read-only t)                 ; @r{to make sure}
(setq forms-field-sep ":")
;; @r{Don't allow multi-line fields.}
(setq forms-multi-line nil)

(setq forms-format-list
      (list
       "====== /etc/passwd ======\n\n"
       "User : "    1
       "   Uid: "   3
       "   Gid: "   4
       "\n\n"
       "Name : "    5
       "\n\n"
       "Home : "    6
       "\n\n"
       "Shell: "    7
       "\n"))
@end example

When you construct the value of  @code{forms-format-list}, you should
usually either quote the whole value, like this,

@example
(setq forms-format-list
     '(
       "====== " forms-file " ======\n\n"
       "User : "    1
       (make-string 20 ?-)
       @dots{}
      ))
@end example

@noindent
or quote the elements which are lists, like this:

@example
(setq forms-format-list
      (list
       "====== " forms-file " ======\n\n"
       "User : "    1
       '(make-string 20 ?-)
       @dots{}
      ))
@end example

Forms mode validates the contents of @code{forms-format-list} when you
visit a database.  If there are errors, processing is aborted with an
error message which includes a descriptive text.  @xref{Error Messages},
for a detailed list of error messages.

If no @code{forms-format-list} is specified, Forms mode will supply a
default format list.  This list contains the name of the file being
visited, and a simple label for each field indicating the field number.

@node Modifying Forms Contents
@chapter Modifying The Forms Contents

If @code{forms-read-only} is @code{nil}, the user can modify the fields
and records of the database.

All normal editing commands are available for editing the contents of the
displayed record.  You cannot delete or modify the fixed, explanatory
text that comes from string formatting elements, but you can modify the
actual field contents.

@ignore
@c This is for the Emacs 18 version only.
If the contents of the forms cannot be recognized properly, this is
signaled using a descriptive text.  @xref{Error Messages}, for more info.
The cursor will indicate the last part of the forms which was
successfully parsed.  It's important to avoid entering field contents
that would cause confusion with the field-separating fixed text.
@end ignore

If the variable @code{forms-modified-record-filter} is non-@code{nil},
it is called as a function before the new data is written to the data
file.  The function receives one argument, a vector that contains the
contents of the fields of the record.

The function can refer to fields with @code{aref} and modify them with
@code{aset}.  The first field has number 1 (one); thus, element 0 of the
vector is not used.  The function should return the same vector it was
passed; the (possibly modified) contents of the vector determine what is
actually written in the file.  Here is an example:

@example
(defun my-modified-record-filter (record)
  ;; @r{Modify second field.}
  (aset record 2 (current-time-string))
  ;; @r{Return the field vector.}
  record)

(setq forms-modified-record-filter 'my-modified-record-filter)
@end example

If the variable @code{forms-new-record-filter} is non-@code{nil}, its
value is a function to be called to fill in default values for the
fields of a new record.  The function is passed a vector of empty
strings, one for each field; it should return the same vector, with
the desired field values stored in it.  Fields are numbered starting
from 1 (one).  Example:

@example
(defun my-new-record-filter (fields)
  (aset fields 5 (login-name))
  (aset fields 1 (current-time-string))
  fields)

(setq forms-new-record-filter 'my-new-record-filter)
@end example

@node Miscellaneous
@chapter Miscellaneous

@vindex forms-version
The global variable @code{forms-version} holds the version information
of the Forms mode software.

@findex forms-enumerate
It is very convenient to use symbolic names for the fields in a record.
The function @code{forms-enumerate} provides an elegant means to define
a series of variables whose values are consecutive integers.  The
function returns the highest number used, so it can be used to set
@code{forms-number-of-fields} also.  For example:

@example
(setq forms-number-of-fields
      (forms-enumerate
       '(field1 field2 field3 @dots{})))
@end example

This sets @code{field1} to 1, @code{field2} to 2, and so on.

Care has been taken to keep the Forms mode variables buffer-local, so it
is possible to visit multiple files in Forms mode simultaneously, even
if they have different properties.

@findex forms-mode
If you have visited the control file in normal fashion with
@code{find-file} or a like command, you can switch to Forms mode with
the command @code{M-x forms-mode}.  If you put @samp{-*- forms -*-} in
the first line of the control file, then visiting it enables Forms mode
automatically.  But this makes it hard to edit the control file itself,
so you'd better think twice before using this.

The default format for the data file, using @code{"\t"} to separate
fields and @code{"\^k"} to separate lines within a field, matches the
file format of some popular database programs, e.g. FileMaker.  So
@code{forms-mode} can decrease the need to use proprietary software.

@node Error Messages
@chapter Error Messages

This section describes all error messages which can be generated by
forms mode.  Error messages that result from parsing the control file
all start with the text @samp{Forms control file error}.  Messages
generated while analyzing the definition of @code{forms-format-list}
start with @samp{Forms format error}.

@table @code
@item Forms control file error: `forms-file' has not been set
The variable @code{forms-file} was not set by the control file.

@item Forms control file error: `forms-number-of-fields' has not been set
The variable @code{forms-number-of-fields} was not set by the control
file.

@item Forms control file error: `forms-number-of-fields' must be a number > 0
The variable @code{forms-number-of-fields} did not contain a positive
number.

@item Forms control file error: `forms-field-sep' is not a string
@itemx Forms control file error: `forms-multi-line' must be nil or a one-character string
The variable @code{forms-multi-line} was set to something other than
@code{nil} or a single-character string.

@item Forms control file error: `forms-multi-line' is equal to 'forms-field-sep'
The variable @code{forms-multi-line} may not be equal to
@code{forms-field-sep} for this would make it impossible to distinguish
fields and the lines in the fields.

@item Forms control file error: `forms-new-record-filter' is not a function
@itemx Forms control file error: `forms-modified-record-filter' is not a function
The variable has been set to something else than a function.

@item Forms control file error: `forms-format-list' is not a list
The variable @code{forms-format-list} was not set to a Lisp list
by the control file.

@item Forms format error: field number @var{xx} out of range 1..@var{nn}
A field number was supplied in @code{forms-format-list} with a value of
@var{xx}, which was not greater than zero and smaller than or equal to
the number of fields in the forms, @var{nn}.

@item Forms format error: @var{fun} is not a function
The first element of a list which is an element of
@code{forms-format-list} was not a valid Lisp function.

@item Forms format error: invalid element @var{xx}
A list element was supplied in @code{forms-format-list} which was not a
string, number or list.

@ignore
@c This applies to Emacs 18 only.
@c Error messages generated while a modified form is being analyzed.

@item Parse error: not looking at `...'
When re-parsing the contents of a forms, the text shown could not
be found.

@item Parse error: cannot find `...'
When re-parsing the contents of a forms, the text shown, which
separates two fields, could not be found.

@item Parse error: cannot parse adjacent fields @var{xx} and @var{yy}
Fields @var{xx} and @var{yy} were not separated by text, so could not be
parsed again.
@end ignore

@item Warning: this record has @var{xx} fields instead of @var{yy}
The number of fields in this record in the data file did not match
@code{forms-number-of-fields}.  Missing fields will be made empty.

@item Multi-line fields in this record - update refused!
The current record contains newline characters, hence can not be written
back to the data file, for it would corrupt it.  Probably you inserted a
newline in a field, while @code{forms-multi-line} was @code{nil}.

@item Field separator occurs in record - update refused!
The current record contains the field separator string inside one of the
fields. It can not be written back to the data file, for it would
corrupt it. Probably you inserted the field separator string in a field.

@item Record number @var{xx} out of range 1..@var{yy}
A jump was made to non-existing record @var{xx}.  @var{yy} denotes the
number of records in the file.

@item Stuck at record @var{xx}
An internal error prevented a specific record from being retrieved.

@item No write access to @code{"}@var{file}@code{"}
An attempt was made to enable edit mode on a file that has been write
protected.

@item Search failed: @var{regexp}
The @var{regexp} could not be found in the data file. Forward searching
is done from the current location until the end of the file, then
retrying from the beginning of the file until the current location.
Backward searching is done from the current location until the beginning
of the file, then retrying from the end of the file until the current
location.

@item Wrapped
A search completed successfully after wrapping around.

@item Warning: number of records changed to @var{nn}
Forms mode's idea of the number of records has been adjusted to the
number of records actually present in the data file.

@item Problem saving buffers?
An error occurred while saving the data file buffer. Most likely, Emacs
did ask to confirm deleting the buffer because it had been modified, and
you said `no'.
@end table

@node Long Example
@chapter Long Example

The following example exploits most of the features of Forms mode.
This example is included in the distribution as file @file{forms-d2.el}.

@example
;; demo2 -- demo forms-mode     -*- emacs-lisp -*-

;; @r{This sample forms exploit most of the features of forms mode.}

;; @r{Set the name of the data file.}
(setq forms-file "forms-d2.dat")

;; @r{Use @code{forms-enumerate} to set field names and number thereof.}
(setq forms-number-of-fields
      (forms-enumerate
       '(arch-newsgroup                 ; 1
         arch-volume                    ; 2
         arch-issue                     ; and ...
         arch-article                   ; ... so
         arch-shortname                 ; ... ... on
         arch-parts
         arch-from
         arch-longname
         arch-keywords
         arch-date
         arch-remarks)))

;; @r{The following functions are used by this form for layout purposes.}
;;
(defun arch-tocol (target &optional fill)
  "Produces a string to skip to column TARGET.
Prepends newline if needed.
The optional FILL should be a character, used to fill to the column."
  (if (null fill)
      (setq fill ? ))
  (if (< target (current-column))
      (concat "\n" (make-string target fill))
    (make-string (- target (current-column)) fill)))
;;
(defun arch-rj (target field &optional fill)
  "Produces a string to skip to column TARGET\
 minus the width of field FIELD.
Prepends newline if needed.
The optional FILL should be a character,
used to fill to the column."
  (arch-tocol (- target (length (nth field forms-fields))) fill))

;; @r{Record filters.}
;;
(defun new-record-filter (the-record)
  "Form a new record with some defaults."
  (aset the-record arch-from (user-full-name))
  (aset the-record arch-date (current-time-string))
  the-record)                           ; return it
(setq forms-new-record-filter 'new-record-filter)

;; @r{The format list.}
(setq forms-format-list
     (list
       "====== Public Domain Software Archive ======\n\n"
       arch-shortname
       " - "                    arch-longname
       "\n\n"
       "Article: "              arch-newsgroup
       "/"                      arch-article
       " "
       '(arch-tocol 40)
       "Issue: "                arch-issue
       " "
       '(arch-rj 73 10)
       "Date: "                 arch-date
       "\n\n"
       "Submitted by: "         arch-from
       "\n"
       '(arch-tocol 79 ?-)
       "\n"
       "Keywords: "             arch-keywords
       "\n\n"
       "Parts: "                arch-parts
       "\n\n====== Remarks ======\n\n"
       arch-remarks
     ))

;; @r{That's all, folks!}
@end example

@node Credits
@chapter Credits

Bug fixes and other useful suggestions were supplied by
Harald Hanche-Olsen (@code{hanche@@imf.unit.no}),
@code{cwitty@@portia.stanford.edu},
Jonathan I. Kamens,
Per Cederqvist  (@code{ceder@@signum.se}),
Michael Lipka (@code{lipka@@lip.hanse.de}),
Andy Piper (@code{ajp@@eng.cam.ac.uk}),
Frederic Pierresteguy  (@code{F.Pierresteguy@@frcl.bull.fr}),
Ignatios Souvatzis
and Richard Stallman (@code{rms@@gnu.org}).

This documentation was slightly inspired by the documentation of ``rolo
mode'' by Paul Davis at Schlumberger Cambridge Research
(@code{davis%scrsu1%sdr.slb.com@@relay.cs.net}).

None of this would have been possible without GNU Emacs of the Free
Software Foundation.  Thanks, Richard!

@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include doclicense.texi

@node Index
@unnumbered Index
@printindex cp

@contents
@bye

@ignore
   arch-tag: 2ac9810b-aa49-4ea6-8030-d7f1ecd467ed
@end ignore