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//usr/share/perl5/CGI/HTML/Functions.pod

=head1 NAME

CGI::HTML::Functions - Documentation for CGI.pm Legacy HTML Functionality

=head1 SYNOPSIS

Nothing here - please do not use this functionality, it is considered to
be legacy and essentially deprecated. This documentation exists solely to
aid in maintenance and migration of legacy code using this functionality
and you are strongly encouraged to migrate away from it. If you are working
on new code you should be using a template engine. For more information see
L<CGI::Alternatives>.

If you really want to continue using the HTML generation functionality of CGI.pm
then you should take a look at L<HTML::Tiny> instead, which may give you a migration
path away from CGI.pm's html generation functions; i strongly encourage you to
move towards template driven page generation for anything involving markup as
it will make porting your app to other frameworks much easier in the long run.

=head1 DESCRIPTION

The documentation here should be considered an addendum to the sections in the
L<CGI> documentation - the sections here are named the same as those within the
CGI perldoc.

=head1 Calling CGI.pm routines

HTML tag functions have both attributes (the attribute="value" pairs within the
tag itself) and contents (the part between the opening and closing pairs). To
distinguish between attributes and contents, CGI.pm uses the convention of
passing HTML attributes as a hash reference as the first argument, and the
contents, if any, as any subsequent arguments.  It works out like
this:

Code                           Generated HTML
    ----                           --------------
    h1()                           <h1 />
    h1('some','contents');         <h1>some contents</h1>
    h1({-align=>left});            <h1 align="LEFT">
    h1({-align=>left},'contents'); <h1 align="LEFT">contents</h1>

Many newcomers to CGI.pm are puzzled by the difference between the calling
conventions for the HTML shortcuts, which require curly braces around the HTML
tag attributes, and the calling conventions for other routines, which manage
to generate attributes without the curly brackets. Don't be confused. As a
convenience the curly braces are optional in all but the HTML shortcuts. If you
like, you can use curly braces when calling any routine that takes named
arguments. For example:

print $q->header( { -type => 'image/gif', -expires => '+3d' } );

If you use warnings, you will be warned that some CGI.pm argument names
conflict with built-in perl functions. The most frequent of these is the
-values argument, used to create multi-valued menus, radio button clusters
and the like. To get around this warning, you have several choices:

=over 4

=item 1.

Use another name for the argument, if one is available. 
For example, -value is an alias for -values.

=item 2.

Change the capitalization, e.g. -Values

=item 3.

Put quotes around the argument name, e.g. '-values'

=back

=head2 Function-oriented interface HTML exports

Here is a list of the HTML related function sets you can import:

=over 4

=item B<:form>

Import all fill-out form generating methods, such as B<textfield()>.

=item B<:html2>

Import all methods that generate HTML 2.0 standard elements.

=item B<:html3>

Import all methods that generate HTML 3.0 elements (such as
<table>, <super> and <sub>).

=item B<:html4>

Import all methods that generate HTML 4 elements (such as
<abbrev>, <acronym> and <thead>).

=item B<:netscape>

Import the <blink>, <fontsize> and <center> tags.

=item B<:html>

Import all HTML-generating shortcuts (i.e. 'html2', 'html3', 'html4' and 'netscape')

=item B<:standard>

Import "standard" features, 'html2', 'html3', 'html4', 'ssl', 'form' and 'cgi'.

=back

If you import any of the state-maintaining CGI or form-generating methods,
a default CGI object will be created and initialized automatically the first
time you use any of the methods that require one to be present. This includes
B<param()>, B<textfield()>, B<submit()> and the like. (If you need direct access
to the CGI object, you can find it in the global variable B<$CGI::Q>).

=head2 Pragmas

Additional HTML generation related pragms:

=over 4

=item -nosticky

By default the CGI module implements a state-preserving behavior called
"sticky" fields. The way this works is that if you are regenerating a form,
the methods that generate the form field values will interrogate param()
to see if similarly-named parameters are present in the query string. If
they find a like-named parameter, they will use it to set their default values.

Sometimes this isn't what you want. The B<-nosticky> pragma prevents this
behavior. You can also selectively change the sticky behavior in each element
that you generate.

=item -tabindex

Automatically add tab index attributes to each form field. With this option
turned off, you can still add tab indexes manually by passing a -tabindex
option to each field-generating method.

=item -no_xhtml

By default, CGI.pm versions 2.69 and higher emit XHTML
(http://www.w3.org/TR/xhtml1/). The -no_xhtml pragma disables this feature.
Thanks to Michalis Kabrianis <kabrianis@hellug.gr> for this feature.

If start_html()'s -dtd parameter specifies an HTML 2.0, 3.2, 4.0 or 4.01 DTD,
XHTML will automatically be disabled without needing to use this pragma.

=back

=head2 Special forms for importing HTML-tag functions

Many of the methods generate HTML tags. As described below, tag functions
automatically generate both the opening and closing tags. For example:

print h1('Level 1 Header');

produces

<h1>Level 1 Header</h1>

There will be some times when you want to produce the start and end tags
yourself. In this case, you can use the form start_I<tag_name> and
end_I<tag_name>, as in:

print start_h1,'Level 1 Header',end_h1;

=head2 Creating the HTML document header

print start_html(
        -title      => 'Secrets of the Pyramids',
        -author     => 'fred@capricorn.org',
        -base       => 'true',
        -target     => '_blank',
        -meta       => {'keywords'=>'pharaoh secret mummy',
        'copyright' => 'copyright 1996 King Tut'},
        -style      => {'src'=>'/styles/style1.css'},
        -BGCOLOR    => 'blue'
    );

The start_html() routine creates the top of the page, along with a lot of
optional information that controls the page's appearance and behavior.

This method returns a canned HTML header and the opening <body> tag. All
parameters are optional. In the named parameter form, recognized parameters
are -title, -author, -base, -xbase, -dtd, -lang and -target (see below for the
explanation). Any additional parameters you provide, such as the unofficial
BGCOLOR attribute, are added to the <body> tag. Additional parameters must be
proceeded by a hyphen.

The argument B<-xbase> allows you to provide an HREF for the <base> tag different
from the current location, as in

-xbase => "http://home.mcom.com/"

All relative links will be interpreted relative to this tag.

The argument B<-target> allows you to provide a default target frame for all the
links and fill-out forms on the page. B<This is a non-standard HTTP feature>
B<which only works with some browsers!>

-target => "answer_window"

All relative links will be interpreted relative to this tag.  You add arbitrary
meta information to the header with the B<-meta> argument. This argument expects
a reference to a hash containing name/value pairs of meta information. These will
be turned into a series of header <meta> tags that look something like this:

To create an HTTP-EQUIV type of <meta> tag, use B<-head>, described below.

The B<-style> argument is used to incorporate cascading stylesheets into your
code. See the section on CASCADING STYLESHEETS for more information.

The B<-lang> argument is used to incorporate a language attribute into the <html>
tag. For example:

print $q->start_html( -lang => 'fr-CA' );

The default if not specified is "en-US" for US English, unless the -dtd parameter
specifies an HTML 2.0 or 3.2 DTD, in which case the lang attribute is left off.
You can force the lang attribute to left off in other cases by passing an empty
string (-lang=>'').

The B<-encoding> argument can be used to specify the character set for XHTML. It
defaults to iso-8859-1 if not specified.

The B<-dtd> argument can be used to specify a public DTD identifier string. For
example:

-dtd => '-//W3C//DTD HTML 4.01 Transitional//EN')

Alternatively, it can take public and system DTD identifiers as an array:

-dtd => [
        '-//W3C//DTD HTML 4.01 Transitional//EN',
        'http://www.w3.org/TR/html4/loose.dtd'
    ]

For the public DTD identifier to be considered, it must be valid. Otherwise it
will be replaced by the default DTD. If the public DTD contains 'XHTML', CGI.pm
will emit XML.

The B<-declare_xml> argument, when used in conjunction with XHTML, will put a
<?xml> declaration at the top of the HTML header. The sole purpose of this
declaration is to declare the character set encoding. In the absence of
-declare_xml, the output HTML will contain a <meta> tag that specifies the
encoding, allowing the HTML to pass most validators. The default for -declare_xml
is false.

You can place other arbitrary HTML elements to the <head> section with the
B<-head> tag.  For example, to place a <link> element in the head section, use
this:

print start_html(
        -head => Link({
            -rel  => 'shortcut icon',
            -href => 'favicon.ico'
        })
    );

To incorporate multiple HTML elements into the <head> section, just pass an
array reference:

print start_html(
        -head => [
            Link({
                -rel  => 'next',
                -href => 'http://www.capricorn.com/s2.html'
            }),
            Link({
                -rel  => 'previous',
                -href => 'http://www.capricorn.com/s1.html'
            })
        ]
    );

And here's how to create an HTTP-EQUIV <meta> tag:

print start_html(
        -head => meta({
            -http_equiv => 'Content-Type',
            -content    => 'text/html'
        })
    );

JAVASCRIPTING: The B<-script>, B<-noScript>, B<-onLoad>, B<-onMouseOver>,
B<-onMouseOut> and B<-onUnload> parameters are used to add JavaScript calls to
your pages. B<-script> should point to a block of text containing JavaScript
function definitions. This block will be placed within a <script> block inside
the HTML (not HTTP) header. The block is placed in the header in order to give
your page a fighting chance of having all its JavaScript functions in place even
if the user presses the stop button before the page has loaded completely. CGI.pm
attempts to format the script in such a way that JavaScript-naive browsers will
not choke on the code: unfortunately there are some browsers that get confused by
it nevertheless.

The B<-onLoad> and B<-onUnload> parameters point to fragments of JavaScript code
to execute when the page is respectively opened and closed by the browser.
Usually these parameters are calls to functions defined in the B<-script> field:

$q = CGI->new;
    print header;
    $JSCRIPT = <<END;
        // Ask a silly question
        function riddle_me_this() {
            var r = prompt(
                "What walks on four legs in the morning, " +
                "two legs in the afternoon, " +
                "and three legs in the evening?"
            );
            response(r);
        }
        // Get a silly answer
        function response(answer) {
            if (answer == "man")
                alert("Right you are!");
            else
                alert("Wrong!  Guess again.");
        }
    END
    print start_html(
        -title  => 'The Riddle of the Sphinx',
        -script => $JSCRIPT
    );

Use the B<-noScript> parameter to pass some HTML text that will be displayed on 
browsers that do not have JavaScript (or browsers where JavaScript is turned
off).

The <script> tag, has several attributes including "type", "charset" and "src".
"src" allows you to keep JavaScript code in an external file. To use these
attributes pass a HASH reference in the B<-script> parameter containing one or
more of -type, -src, or -code:

print $q->start_html(
        -title  => 'The Riddle of the Sphinx',
        -script => {
            -type => 'JAVASCRIPT',
            -src  => '/javascript/sphinx.js'}
        );

print $q->(
        -title  => 'The Riddle of the Sphinx',
        -script => {
            -type => 'PERLSCRIPT',
            -code => 'print "hello world!\n;"'
        }
    );

A final feature allows you to incorporate multiple <script> sections into the
header. Just pass the list of script sections as an array reference. This allows
you to specify different source files for different dialects of JavaScript.
Example:

print $q->start_html(
        -title  => 'The Riddle of the Sphinx',
        -script => [
            {
                -type => 'text/javascript',
                -src  => '/javascript/utilities10.js'
            },
            {
                -type => 'text/javascript',
                -src  => '/javascript/utilities11.js'
            },
            {
                -type => 'text/jscript',
                -src  => '/javascript/utilities12.js'
            },
            {
                -type => 'text/ecmascript',
                -src  => '/javascript/utilities219.js'
            }
        ]
    );

The option "-language" is a synonym for -type, and is supported for backwards
compatibility.

The old-style positional parameters are as follows:

B<Parameters:>

=over 4

=item 1.

The title

=item 2.

The author's e-mail address (will create a <link rev="MADE"> tag if present

=item 3.

A 'true' flag if you want to include a <base> tag in the header. This helps
resolve relative addresses to absolute ones when the document is moved, but
makes the document hierarchy non-portable. Use with care!

=back

Other parameters you want to include in the <body> tag may be appended to these.
This is a good place to put HTML extensions, such as colors and wallpaper
patterns.

=head2 Ending the Html document:

print $q->end_html;

This ends an HTML document by printing the </body></html> tags.

=head1 CREATING STANDARD HTML ELEMENTS:

CGI.pm defines general HTML shortcut methods for many HTML tags.  HTML shortcuts are named after a single
HTML element and return a fragment of HTML text. Example:

print $q->blockquote(
		     "Many years ago on the island of",
		     $q->a({href=>"http://crete.org/"},"Crete"),
		     "there lived a Minotaur named",
		     $q->strong("Fred."),
		    ),
       $q->hr;

This results in the following HTML code (extra newlines have been
added for readability):

<blockquote>
   Many years ago on the island of
   <a href="http://crete.org/">Crete</a> there lived
   a minotaur named <strong>Fred.</strong> 
   </blockquote>
   <hr>

If you find the syntax for calling the HTML shortcuts awkward, you can
import them into your namespace and dispense with the object syntax
completely (see the next section for more details):

use CGI ':standard';
   print blockquote(
      "Many years ago on the island of",
      a({href=>"http://crete.org/"},"Crete"),
      "there lived a minotaur named",
      strong("Fred."),
      ),
      hr;

=head2 Providing arguments to HTML shortcuts

The HTML methods will accept zero, one or multiple arguments.  If you
provide no arguments, you get a single tag:

print hr;  	#  <hr>

If you provide one or more string arguments, they are concatenated
together with spaces and placed between opening and closing tags:

print h1("Chapter","1"); # <h1>Chapter 1</h1>"

If the first argument is a hash reference, then the keys
and values of the hash become the HTML tag's attributes:

print a({-href=>'fred.html',-target=>'_new'},
      "Open a new frame");

<a href="fred.html",target="_new">Open a new frame</a>

You may dispense with the dashes in front of the attribute names if
you prefer:

print img {src=>'fred.gif',align=>'LEFT'};

Sometimes an HTML tag attribute has no argument.  For example, ordered
lists can be marked as COMPACT.  The syntax for this is an argument that
that points to an undef string:

print ol({compact=>undef},li('one'),li('two'),li('three'));

Prior to CGI.pm version 2.41, providing an empty ('') string as an
attribute argument was the same as providing undef.  However, this has
changed in order to accommodate those who want to create tags of the form 
<img alt="">.  The difference is shown in these two pieces of code:

CODE                   RESULT
   img({alt=>undef})      <img alt>
   img({alt=>''})         <img alt="">

=head2 The distributive property of HTML shortcuts

One of the cool features of the HTML shortcuts is that they are
distributive.  If you give them an argument consisting of a
B<reference> to a list, the tag will be distributed across each
element of the list.  For example, here's one way to make an ordered
list:

print ul(
             li({-type=>'disc'},['Sneezy','Doc','Sleepy','Happy'])
           );

This example will result in HTML output that looks like this:

<ul>
     <li type="disc">Sneezy</li>
     <li type="disc">Doc</li>
     <li type="disc">Sleepy</li>
     <li type="disc">Happy</li>
   </ul>

This is extremely useful for creating tables.  For example:

print table({-border=>undef},
           caption('When Should You Eat Your Vegetables?'),
           Tr({-align=>'CENTER',-valign=>'TOP'},
           [
              th(['Vegetable', 'Breakfast','Lunch','Dinner']),
              td(['Tomatoes' , 'no', 'yes', 'yes']),
              td(['Broccoli' , 'no', 'no',  'yes']),
              td(['Onions'   , 'yes','yes', 'yes'])
           ]
           )
        );

=head2 HTML shortcuts and list interpolation

Consider this bit of code:

print blockquote(em('Hi'),'mom!'));

It will ordinarily return the string that you probably expect, namely:

Note the space between the element "Hi" and the element "mom!".
CGI.pm puts the extra space there using array interpolation, which is
controlled by the magic $" variable.  Sometimes this extra space is
not what you want, for example, when you are trying to align a series
of images.  In this case, you can simply change the value of $" to an
empty string.

{
      local($") = '';
      print blockquote(em('Hi'),'mom!'));
    }

I suggest you put the code in a block as shown here.  Otherwise the
change to $" will affect all subsequent code until you explicitly
reset it.

=head2 Non-standard HTML shortcuts

A few HTML tags don't follow the standard pattern for various
reasons.

B<comment()> generates an HTML comment ().  Call it
like

print comment('here is my comment');

Because of conflicts with built-in perl functions, the following functions
begin with initial caps:

Select
    Tr
    Link
    Delete
    Accept
    Sub

In addition, start_html(), end_html(), start_form(), end_form(),
start_multipart_form() and all the fill-out form tags are special.
See their respective sections.

=head2 Autoescaping HTML

By default, all HTML that is emitted by the form-generating functions
is passed through a function called escapeHTML():

=over 4

=item $escaped_string = escapeHTML("unescaped string");

Escape HTML formatting characters in a string. Internally this calls
L<HTML::Entities> (encode_entities) so really you should just use that
instead - the default list of chars that will be encoded (passed to the
HTML::Entities encode_entities method) is:

& < > " \x8b \x9b '

you can control this list by setting the value of $CGI::ENCODE_ENTITIES:

# only encode < >
    $CGI::ENCODE_ENTITIES = q{<>}

if you want to encode B<all> entities then undef $CGI::ENCODE_ENTITIES:

# encode all entities
    $CGI::ENCODE_ENTITIES = undef;

=back

The automatic escaping does not apply to other shortcuts, such as
h1().  You should call escapeHTML() yourself on untrusted data in
order to protect your pages against nasty tricks that people may enter
into guestbooks, etc..  To change the character set, use charset().
To turn autoescaping off completely, use autoEscape(0):

=over 4

=item $charset = charset([$charset]);

Get or set the current character set.

=item $flag = autoEscape([$flag]);

Get or set the value of the autoescape flag.

=back

=head1 CREATING FILL-OUT FORMS:

I<General note>  The various form-creating methods all return strings
to the caller, containing the tag or tags that will create the requested
form element.  You are responsible for actually printing out these strings.
It's set up this way so that you can place formatting tags
around the form elements.

I<Another note> The default values that you specify for the forms are only
used the B<first> time the script is invoked (when there is no query
string).  On subsequent invocations of the script (when there is a query
string), the former values are used even if they are blank.

If you want to change the value of a field from its previous value, you have two
choices:

(1) call the param() method to set it.

(2) use the -override (alias -force) parameter (a new feature in version 2.15).
This forces the default value to be used, regardless of the previous value:

print textfield(-name=>'field_name',
			   -default=>'starting value',
			   -override=>1,
			   -size=>50,
			   -maxlength=>80);

I<Yet another note> By default, the text and labels of form elements are
escaped according to HTML rules.  This means that you can safely use
"<CLICK ME>" as the label for a button.  However, it also interferes with
your ability to incorporate special HTML character sequences, such as &Aacute;,
into your fields.  If you wish to turn off automatic escaping, call the
autoEscape() method with a false value immediately after creating the CGI object:

$q = CGI->new;
   $q->autoEscape(0);

Note that autoEscape() is exclusively used to effect the behavior of how some
CGI.pm HTML generation functions handle escaping. Calling escapeHTML()
explicitly will always escape the HTML.

I<A Lurking Trap!> Some of the form-element generating methods return
multiple tags.  In a scalar context, the tags will be concatenated
together with spaces, or whatever is the current value of the $"
global.  In a list context, the methods will return a list of
elements, allowing you to modify them if you wish.  Usually you will
not notice this behavior, but beware of this:

printf("%s\n",end_form())

end_form() produces several tags, and only the first of them will be
printed because the format only expects one value.

<p>

=head2 Creating an isindex tag

print isindex(-action=>$action);

-or-

print isindex($action);

Prints out an <isindex> tag.  Not very exciting.  The parameter
-action specifies the URL of the script to process the query.  The
default is to process the query with the current script.

=head2 Starting and ending a form

print start_form(-method=>$method,
		    -action=>$action,
		    -enctype=>$encoding);
      <... various form stuff ...>
    print end_form;

-or-

print start_form($method,$action,$encoding);
      <... various form stuff ...>
    print end_form;

start_form() will return a <form> tag with the optional method,
action and form encoding that you specify.  The defaults are:

method: POST
    action: this script
    enctype: application/x-www-form-urlencoded for non-XHTML
             multipart/form-data for XHTML, see multipart/form-data below.

end_form() returns the closing </form> tag.

start_form()'s enctype argument tells the browser how to package the various
fields of the form before sending the form to the server.  Two
values are possible:

=over 4

=item B<application/x-www-form-urlencoded>

This is the older type of encoding.  It is compatible with many CGI scripts and is
suitable for short fields containing text data.  For your
convenience, CGI.pm stores the name of this encoding
type in B<&CGI::URL_ENCODED>.

=item B<multipart/form-data>

This is the newer type of encoding.
It is suitable for forms that contain very large fields or that
are intended for transferring binary data.  Most importantly,
it enables the "file upload" feature.  For
your convenience, CGI.pm stores the name of this encoding type
in B<&CGI::MULTIPART>

Forms that use this type of encoding are not easily interpreted
by CGI scripts unless they use CGI.pm or another library designed
to handle them.

If XHTML is activated (the default), then forms will be automatically
created using this type of encoding.

=back

The start_form() method uses the older form of encoding by
default unless XHTML is requested.  If you want to use the
newer form of encoding by default, you can call
B<start_multipart_form()> instead of B<start_form()>.  The
method B<end_multipart_form()> is an alias to B<end_form()>.

JAVASCRIPTING: The B<-name> and B<-onSubmit> parameters are provided
for use with JavaScript.  The -name parameter gives the
form a name so that it can be identified and manipulated by
JavaScript functions.  -onSubmit should point to a JavaScript
function that will be executed just before the form is submitted to your
server.  You can use this opportunity to check the contents of the form 
for consistency and completeness.  If you find something wrong, you
can put up an alert box or maybe fix things up yourself.  You can 
abort the submission by returning false from this function.

Usually the bulk of JavaScript functions are defined in a <script>
block in the HTML header and -onSubmit points to one of these function
call.  See start_html() for details.

=head2 Form elements

After starting a form, you will typically create one or more
textfields, popup menus, radio groups and other form elements.  Each
of these elements takes a standard set of named arguments.  Some
elements also have optional arguments.  The standard arguments are as
follows:

=over 4

=item B<-name>

The name of the field. After submission this name can be used to
retrieve the field's value using the param() method.

=item B<-value>, B<-values>

The initial value of the field which will be returned to the script
after form submission.  Some form elements, such as text fields, take
a single scalar -value argument. Others, such as popup menus, take a
reference to an array of values. The two arguments are synonyms.

=item B<-tabindex>

A numeric value that sets the order in which the form element receives
focus when the user presses the tab key. Elements with lower values
receive focus first.

=item B<-id>

A string identifier that can be used to identify this element to
JavaScript and DHTML.

=item B<-override>

A boolean, which, if true, forces the element to take on the value
specified by B<-value>, overriding the sticky behavior described
earlier for the B<-nosticky> pragma.

=item B<-onChange>, B<-onFocus>, B<-onBlur>, B<-onMouseOver>, B<-onMouseOut>, B<-onSelect>

These are used to assign JavaScript event handlers. See the
JavaScripting section for more details.

=back

Other common arguments are described in the next section. In addition
to these, all attributes described in the HTML specifications are
supported.

=head2 Creating a text field

print textfield(-name=>'field_name',
		    -value=>'starting value',
		    -size=>50,
		    -maxlength=>80);
	-or-

print textfield('field_name','starting value',50,80);

textfield() will return a text input field.

B<Parameters>

=over 4

=item 1.

The first parameter is the required name for the field (-name).

=item 2.

The optional second parameter is the default starting value for the field
contents (-value, formerly known as -default).

=item 3.

The optional third parameter is the size of the field in
      characters (-size).

=item 4.

The optional fourth parameter is the maximum number of characters the
      field will accept (-maxlength).

=back

As with all these methods, the field will be initialized with its 
previous contents from earlier invocations of the script.
When the form is processed, the value of the text field can be
retrieved with:

$value = param('foo');

If you want to reset it from its initial value after the script has been
called once, you can do so like this:

param('foo',"I'm taking over this value!");

=head2 Creating a big text field

print textarea(-name=>'foo',
			  -default=>'starting value',
			  -rows=>10,
			  -columns=>50);

-or

print textarea('foo','starting value',10,50);

textarea() is just like textfield, but it allows you to specify
rows and columns for a multiline text entry box.  You can provide
a starting value for the field, which can be long and contain
multiple lines.

=head2 Creating a password field

print password_field(-name=>'secret',
				-value=>'starting value',
				-size=>50,
				-maxlength=>80);
	-or-

print password_field('secret','starting value',50,80);

password_field() is identical to textfield(), except that its contents 
will be starred out on the web page.

=head2 Creating a file upload field

print filefield(-name=>'uploaded_file',
			    -default=>'starting value',
			    -size=>50,
			    -maxlength=>80);
	-or-

print filefield('uploaded_file','starting value',50,80);

filefield() will return a file upload field.
In order to take full advantage of this I<you must use the new 
multipart encoding scheme> for the form.  You can do this either
by calling B<start_form()> with an encoding type of B<&CGI::MULTIPART>,
or by calling the new method B<start_multipart_form()> instead of
vanilla B<start_form()>.

B<Parameters>

=over 4

=item 1.

The first parameter is the required name for the field (-name).

=item 2.

The optional second parameter is the starting value for the field contents
to be used as the default file name (-default).

For security reasons, browsers don't pay any attention to this field,
and so the starting value will always be blank.  Worse, the field
loses its "sticky" behavior and forgets its previous contents.  The
starting value field is called for in the HTML specification, however,
and possibly some browser will eventually provide support for it.

=item 3.

The optional third parameter is the size of the field in
characters (-size).

=item 4.

The optional fourth parameter is the maximum number of characters the
field will accept (-maxlength).

=back

JAVASCRIPTING: The B<-onChange>, B<-onFocus>, B<-onBlur>,
B<-onMouseOver>, B<-onMouseOut> and B<-onSelect> parameters are
recognized.  See textfield() for details.

=head2 Creating a popup menu

print popup_menu('menu_name',
			    ['eenie','meenie','minie'],
			    'meenie');

-or-

%labels = ('eenie'=>'your first choice',
	      'meenie'=>'your second choice',
	      'minie'=>'your third choice');
   %attributes = ('eenie'=>{'class'=>'class of first choice'});
   print popup_menu('menu_name',
			    ['eenie','meenie','minie'],
          'meenie',\%labels,\%attributes);

-or (named parameter style)-

print popup_menu(-name=>'menu_name',
			    -values=>['eenie','meenie','minie'],
			    -default=>['meenie','minie'],
          -labels=>\%labels,
          -attributes=>\%attributes);

popup_menu() creates a menu. Please note that the -multiple option will be
ignored if passed - use scrolling_list() if you want to create a menu that
supports multiple selections

=over 4

=item 1.

The required first argument is the menu's name (-name).

=item 2.

The required second argument (-values) is an array B<reference>
containing the list of menu items in the menu.  You can pass the
method an anonymous array, as shown in the example, or a reference to
a named array, such as "\@foo".

=item 3.

The optional third parameter (-default) is the name of the default
menu choice.  If not specified, the first item will be the default.
The values of the previous choice will be maintained across
queries. Pass an array reference to select multiple defaults.

=item 4.

The optional fourth parameter (-labels) is provided for people who
want to use different values for the user-visible label inside the
popup menu and the value returned to your script.  It's a pointer to an
hash relating menu values to user-visible labels.  If you
leave this parameter blank, the menu values will be displayed by
default.  (You can also leave a label undefined if you want to).

=item 5.

The optional fifth parameter (-attributes) is provided to assign
any of the common HTML attributes to an individual menu item. It's
a pointer to a hash relating menu values to another
hash with the attribute's name as the key and the
attribute's value as the value.

=back

When the form is processed, the selected value of the popup menu can
be retrieved using:

$popup_menu_value = param('menu_name');

=head2 Creating an option group

Named parameter style

print popup_menu(-name=>'menu_name',
                  -values=>[qw/eenie meenie minie/,
                            optgroup(-name=>'optgroup_name',
                                             -values => ['moe','catch'],
                                             -attributes=>{'catch'=>{'class'=>'red'}})],
                  -labels=>{'eenie'=>'one',
                            'meenie'=>'two',
                            'minie'=>'three'},
                  -default=>'meenie');

Old style
  print popup_menu('menu_name',
                  ['eenie','meenie','minie',
                   optgroup('optgroup_name', ['moe', 'catch'],
                                   {'catch'=>{'class'=>'red'}})],'meenie',
                  {'eenie'=>'one','meenie'=>'two','minie'=>'three'});

optgroup() creates an option group within a popup menu.

=over 4

=item 1.

The required first argument (B<-name>) is the label attribute of the
optgroup and is B<not> inserted in the parameter list of the query.

=item 2.

The required second argument (B<-values>)  is an array reference
containing the list of menu items in the menu.  You can pass the
method an anonymous array, as shown in the example, or a reference
to a named array, such as \@foo.  If you pass a HASH reference,
the keys will be used for the menu values, and the values will be
used for the menu labels (see -labels below).

=item 3.

The optional third parameter (B<-labels>) allows you to pass a reference
to a hash containing user-visible labels for one or more
of the menu items.  You can use this when you want the user to see one
menu string, but have the browser return your program a different one.
If you don't specify this, the value string will be used instead
("eenie", "meenie" and "minie" in this example).  This is equivalent
to using a hash reference for the -values parameter.

=item 4.

An optional fourth parameter (B<-labeled>) can be set to a true value
and indicates that the values should be used as the label attribute
for each option element within the optgroup.

=item 5.

An optional fifth parameter (-novals) can be set to a true value and
indicates to suppress the val attribute in each option element within
the optgroup.

See the discussion on optgroup at W3C
(http://www.w3.org/TR/REC-html40/interact/forms.html#edef-OPTGROUP)
for details.

=item 6.

An optional sixth parameter (-attributes) is provided to assign
any of the common HTML attributes to an individual menu item. It's
a pointer to a hash relating menu values to another
hash with the attribute's name as the key and the
attribute's value as the value.

=back

=head2 Creating a scrolling list

print scrolling_list('list_name',
				['eenie','meenie','minie','moe'],
        ['eenie','moe'],5,'true',{'moe'=>{'class'=>'red'}});
      -or-

print scrolling_list('list_name',
				['eenie','meenie','minie','moe'],
				['eenie','moe'],5,'true',
        \%labels,%attributes);

-or-

print scrolling_list(-name=>'list_name',
				-values=>['eenie','meenie','minie','moe'],
				-default=>['eenie','moe'],
				-size=>5,
				-multiple=>'true',
        -labels=>\%labels,
        -attributes=>\%attributes);

scrolling_list() creates a scrolling list.

B<Parameters:>

=over 4

=item 1.

The first and second arguments are the list name (-name) and values
(-values).  As in the popup menu, the second argument should be an
array reference.

=item 2.

The optional third argument (-default) can be either a reference to a
list containing the values to be selected by default, or can be a
single value to select.  If this argument is missing or undefined,
then nothing is selected when the list first appears.  In the named
parameter version, you can use the synonym "-defaults" for this
parameter.

=item 3.

The optional fourth argument is the size of the list (-size).

=item 4.

The optional fifth argument can be set to true to allow multiple
simultaneous selections (-multiple).  Otherwise only one selection
will be allowed at a time.

=item 5.

The optional sixth argument is a pointer to a hash
containing long user-visible labels for the list items (-labels).
If not provided, the values will be displayed.

=item 6.

The optional sixth parameter (-attributes) is provided to assign
any of the common HTML attributes to an individual menu item. It's
a pointer to a hash relating menu values to another
hash with the attribute's name as the key and the
attribute's value as the value.

When this form is processed, all selected list items will be returned as
a list under the parameter name 'list_name'.  The values of the
selected items can be retrieved with:

@selected = param('list_name');

=back

=head2 Creating a group of related checkboxes

print checkbox_group(-name=>'group_name',
				-values=>['eenie','meenie','minie','moe'],
				-default=>['eenie','moe'],
				-linebreak=>'true',
                                -disabled => ['moe'],
        -labels=>\%labels,
        -attributes=>\%attributes);

print checkbox_group('group_name',
				['eenie','meenie','minie','moe'],
        ['eenie','moe'],'true',\%labels,
        {'moe'=>{'class'=>'red'}});

HTML3-COMPATIBLE BROWSERS ONLY:

print checkbox_group(-name=>'group_name',
				-values=>['eenie','meenie','minie','moe'],
				-rows=2,-columns=>2);

checkbox_group() creates a list of checkboxes that are related
by the same name.

B<Parameters:>

=over 4

=item 1.

The first and second arguments are the checkbox name and values,
respectively (-name and -values).  As in the popup menu, the second
argument should be an array reference.  These values are used for the
user-readable labels printed next to the checkboxes as well as for the
values passed to your script in the query string.

=item 2.

The optional third argument (-default) can be either a reference to a
list containing the values to be checked by default, or can be a
single value to checked.  If this argument is missing or undefined,
then nothing is selected when the list first appears.

=item 3.

The optional fourth argument (-linebreak) can be set to true to place
line breaks between the checkboxes so that they appear as a vertical
list.  Otherwise, they will be strung together on a horizontal line.

=back

The optional B<-labels> argument is a pointer to a hash
relating the checkbox values to the user-visible labels that will be
printed next to them.  If not provided, the values will be used as the
default.

The optional parameters B<-rows>, and B<-columns> cause
checkbox_group() to return an HTML3 compatible table containing the
checkbox group formatted with the specified number of rows and
columns.  You can provide just the -columns parameter if you wish;
checkbox_group will calculate the correct number of rows for you.

The option B<-disabled> takes an array of checkbox values and disables
them by greying them out (this may not be supported by all browsers).

The optional B<-attributes> argument is provided to assign any of the
common HTML attributes to an individual menu item. It's a pointer to
a hash relating menu values to another hash
with the attribute's name as the key and the attribute's value as the
value.

The optional B<-tabindex> argument can be used to control the order in which
radio buttons receive focus when the user presses the tab button.  If
passed a scalar numeric value, the first element in the group will
receive this tab index and subsequent elements will be incremented by
one.  If given a reference to an array of radio button values, then
the indexes will be jiggered so that the order specified in the array
will correspond to the tab order.  You can also pass a reference to a
hash in which the hash keys are the radio button values and the values
are the tab indexes of each button.  Examples:

-tabindex => 100    #  this group starts at index 100 and counts up
  -tabindex => ['moe','minie','eenie','meenie']  # tab in this order
  -tabindex => {meenie=>100,moe=>101,minie=>102,eenie=>200} # tab in this order

The optional B<-labelattributes> argument will contain attributes
attached to the <label> element that surrounds each button.

When the form is processed, all checked boxes will be returned as
a list under the parameter name 'group_name'.  The values of the
"on" checkboxes can be retrieved with:

@turned_on = param('group_name');

The value returned by checkbox_group() is actually an array of button
elements.  You can capture them and use them within tables, lists,
or in other creative ways:

@h = checkbox_group(-name=>'group_name',-values=>\@values);
    &use_in_creative_way(@h);

=head2 Creating a standalone checkbox

print checkbox(-name=>'checkbox_name',
			   -checked=>1,
			   -value=>'ON',
			   -label=>'CLICK ME');

-or-

print checkbox('checkbox_name','checked','ON','CLICK ME');

checkbox() is used to create an isolated checkbox that isn't logically
related to any others.

B<Parameters:>

=over 4

=item 1.

The first parameter is the required name for the checkbox (-name).  It
will also be used for the user-readable label printed next to the
checkbox.

=item 2.

The optional second parameter (-checked) specifies that the checkbox
is turned on by default.  Synonyms are -selected and -on.

=item 3.

The optional third parameter (-value) specifies the value of the
checkbox when it is checked.  If not provided, the word "on" is
assumed.

=item 4.

The optional fourth parameter (-label) is the user-readable label to
be attached to the checkbox.  If not provided, the checkbox name is
used.

=back

The value of the checkbox can be retrieved using:

$turned_on = param('checkbox_name');

=head2 Creating a radio button group

print radio_group(-name=>'group_name',
			     -values=>['eenie','meenie','minie'],
			     -default=>'meenie',
			     -linebreak=>'true',
           -labels=>\%labels,
           -attributes=>\%attributes);

-or-

print radio_group('group_name',['eenie','meenie','minie'],
            'meenie','true',\%labels,\%attributes);

HTML3-COMPATIBLE BROWSERS ONLY:

print radio_group(-name=>'group_name',
			     -values=>['eenie','meenie','minie','moe'],
			     -rows=2,-columns=>2);

radio_group() creates a set of logically-related radio buttons
(turning one member of the group on turns the others off)

B<Parameters:>

=over 4

=item 1.

The first argument is the name of the group and is required (-name).

=item 2.

The second argument (-values) is the list of values for the radio
buttons.  The values and the labels that appear on the page are
identical.  Pass an array I<reference> in the second argument, either
using an anonymous array, as shown, or by referencing a named array as
in "\@foo".

=item 3.

The optional third parameter (-default) is the name of the default
button to turn on. If not specified, the first item will be the
default.  You can provide a nonexistent button name, such as "-" to
start up with no buttons selected.

=item 4.

The optional fourth parameter (-linebreak) can be set to 'true' to put
line breaks between the buttons, creating a vertical list.

=item 5.

The optional fifth parameter (-labels) is a pointer to an associative
array relating the radio button values to user-visible labels to be
used in the display.  If not provided, the values themselves are
displayed.

=back

All modern browsers can take advantage of the optional parameters
B<-rows>, and B<-columns>.  These parameters cause radio_group() to
return an HTML3 compatible table containing the radio group formatted
with the specified number of rows and columns.  You can provide just
the -columns parameter if you wish; radio_group will calculate the
correct number of rows for you.

To include row and column headings in the returned table, you
can use the B<-rowheaders> and B<-colheaders> parameters.  Both
of these accept a pointer to an array of headings to use.
The headings are just decorative.  They don't reorganize the
interpretation of the radio buttons -- they're still a single named
unit.

The optional B<-labelattributes> argument will contain attributes
attached to the <label> element that surrounds each button.

When the form is processed, the selected radio button can
be retrieved using:

$which_radio_button = param('group_name');

The value returned by radio_group() is actually an array of button
elements.  You can capture them and use them within tables, lists,
or in other creative ways:

@h = radio_group(-name=>'group_name',-values=>\@values);
    &use_in_creative_way(@h);

=head2 Creating a submit button

print submit(-name=>'button_name',
			-value=>'value');

-or-

print submit('button_name','value');

submit() will create the query submission button.  Every form
should have one of these.

B<Parameters:>

=over 4

=item 1.

The first argument (-name) is optional.  You can give the button a
name if you have several submission buttons in your form and you want
to distinguish between them.

=item 2.

The second argument (-value) is also optional.  This gives the button
a value that will be passed to your script in the query string. The
name will also be used as the user-visible label.

=item 3.

You can use -label as an alias for -value.  I always get confused
about which of -name and -value changes the user-visible label on the
button.

=back

You can figure out which button was pressed by using different
values for each one:

$which_one = param('button_name');

=head2 Creating a reset button

print reset

reset() creates the "reset" button.  Note that it restores the
form to its value from the last time the script was called, 
NOT necessarily to the defaults.

Note that this conflicts with the perl reset() built-in.  Use
CORE::reset() to get the original reset function.

=head2 Creating a default button

print defaults('button_label')

defaults() creates a button that, when invoked, will cause the
form to be completely reset to its defaults, wiping out all the
changes the user ever made.

=head2 Creating a hidden field

print hidden(-name=>'hidden_name',
			     -default=>['value1','value2'...]);

-or-

print hidden('hidden_name','value1','value2'...);

hidden() produces a text field that can't be seen by the user.  It
is useful for passing state variable information from one invocation
of the script to the next.

B<Parameters:>

=over 4

=item 1.

The first argument is required and specifies the name of this
field (-name).

=item 2.

The second argument is also required and specifies its value
(-default).  In the named parameter style of calling, you can provide
a single value here or a reference to a whole list

=back

Fetch the value of a hidden field this way:

$hidden_value = param('hidden_name');

Note, that just like all the other form elements, the value of a
hidden field is "sticky".  If you want to replace a hidden field with
some other values after the script has been called once you'll have to
do it manually:

param('hidden_name','new','values','here');

=head2 Creating a clickable image button

print image_button(-name=>'button_name',
				-src=>'/source/URL',
				-align=>'MIDDLE');

-or-

print image_button('button_name','/source/URL','MIDDLE');

image_button() produces a clickable image.  When it's clicked on the
position of the click is returned to your script as "button_name.x"
and "button_name.y", where "button_name" is the name you've assigned
to it.

B<Parameters:>

=over 4

=item 1.

The first argument (-name) is required and specifies the name of this
field.

=item 2.

The second argument (-src) is also required and specifies the URL

=item 3.

The third option (-align, optional) is an alignment type, and may be
TOP, BOTTOM or MIDDLE

=back

Fetch the value of the button this way:
     $x = param('button_name.x');
     $y = param('button_name.y');

=head2 Creating a javascript action button

print button(-name=>'button_name',
			  -value=>'user visible label',
			  -onClick=>"do_something()");

-or-

print button('button_name',"user visible value","do_something()");

button() produces an C<< <input> >> tag with C<type="button">.  When it's
pressed the fragment of JavaScript code pointed to by the B<-onClick> parameter
will be executed.

=head1 WORKING WITH FRAMES

It's possible for CGI.pm scripts to write into several browser panels
and windows using the HTML 4 frame mechanism.  There are three
techniques for defining new frames programmatically:

=over 4

=item 1. Create a <Frameset> document

After writing out the HTTP header, instead of creating a standard
HTML document using the start_html() call, create a <frameset> 
document that defines the frames on the page.  Specify your script(s)
(with appropriate parameters) as the SRC for each of the frames.

There is no specific support for creating <frameset> sections 
in CGI.pm, but the HTML is very simple to write.

=item 2. Specify the destination for the document in the HTTP header

You may provide a B<-target> parameter to the header() method:

print header(-target=>'ResultsWindow');

This will tell the browser to load the output of your script into the
frame named "ResultsWindow".  If a frame of that name doesn't already
exist, the browser will pop up a new window and load your script's
document into that.  There are a number of magic names that you can
use for targets.  See the HTML C<< <frame> >> documentation for details.

=item 3. Specify the destination for the document in the <form> tag

You can specify the frame to load in the FORM tag itself.  With
CGI.pm it looks like this:

print start_form(-target=>'ResultsWindow');

When your script is reinvoked by the form, its output will be loaded
into the frame named "ResultsWindow".  If one doesn't already exist
a new window will be created.

=back

The script "frameset.cgi" in the examples directory shows one way to
create pages in which the fill-out form and the response live in
side-by-side frames.

=head1 SUPPORT FOR JAVASCRIPT

The usual way to use JavaScript is to define a set of functions in a
<SCRIPT> block inside the HTML header and then to register event
handlers in the various elements of the page. Events include such
things as the mouse passing over a form element, a button being
clicked, the contents of a text field changing, or a form being
submitted. When an event occurs that involves an element that has
registered an event handler, its associated JavaScript code gets
called.

The elements that can register event handlers include the <BODY> of an
HTML document, hypertext links, all the various elements of a fill-out
form, and the form itself. There are a large number of events, and
each applies only to the elements for which it is relevant. Here is a
partial list:

=over 4

=item B<onLoad>

The browser is loading the current document. Valid in:

+ The HTML <BODY> section only.

=item B<onUnload>

The browser is closing the current page or frame. Valid for:

+ The HTML <BODY> section only.

=item B<onSubmit>

The user has pressed the submit button of a form. This event happens
just before the form is submitted, and your function can return a
value of false in order to abort the submission.  Valid for:

+ Forms only.

=item B<onClick>

The mouse has clicked on an item in a fill-out form. Valid for:

+ Buttons (including submit, reset, and image buttons)
     + Checkboxes
     + Radio buttons

=item B<onChange>

The user has changed the contents of a field. Valid for: