Koos Pol > CGI-Widget-Tabs-1.07 > CGI::Widget::Tabs

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NAME ^

CGI::Widget::Tabs - Create tab widgets in HTML

SYNOPSIS ^

    use CGI::Widget::Tabs;
    my $tab = CGI::Widget::Tabs->new;

    use CGI;
    my $cgi = CGI->new;          # interface to the query params

    $tab->headings(@titles);     # e.g. qw/Drivers Cars Courses/
    $tab->default("Courses");    # the default active tab
    $tab->active;                # the currently active tab
    $tab->class("my_tab");       # the CSS class to use for markup
    $tab->cgi_object($cgi);      # the object holding the query params
    $tab->cgi_param("t");        # the CGI query parameter to use
    $tab->wrap(4);               # wrap after 4 headings...
    $tab->indent(1);             # ...and add indentation
    $tab->render;                # the resulting HTML code
    $tab->display;               # same as `print $tab->render'


    $h = $tab->heading;               # new OO heading for this tab
    $h->text("TV Listings");          # heading text
    $h->key("tv");                    # key identifying this heading
    $h->raw(1);                       # switch off HTML encoding
    $h->url("whatsontonight.com");    # redirect URL for this heading
    $h->class("red");                 # this heading has it's own class

    # See the EXAMPLE section for a complete example

DESCRIPTION ^

Introduction

CGI::Widget::Tabs lets you simulate tab widgets in HTML. You could benefit from a tab widget if you want to serve only one page. Depending on the tab selected you fetch and display the underlying data. There are three main reasons for taking this approach:

1. For the end user not to be directed to YAL or YAP (yet another link / yet another page), but keep it all together: The single point of entry paradigm.

2. As a consequence the end user deals with a more consistent and integrated GUI. This will give a better "situational awareness" within the application.

3. For the Perl hacker to handle multiple related data sources within the same script environment.

As an example the following tabs could be used on a web page for someone's spotting hobby:

      __________      __________      __________
     /  Planes  \    /  Trains  \    / Classics \
------------------------------------------------------
         _________
        /  Bikes  \
------------------------

As you can see, the headings wrap at three and a small indentation is added to the start of the next row. The nice thing about CGI::Widget::Tabs is that the tabs know their internal state. So you can ask a tab for instance which heading has been clicked by the user. This way you get instant feedback.

"Hey Gorgeous!"

Of course tabs are useless if you can't "see" them. Without proper make up they print as ordinary text. So you really need to fancy them up with some eye candy. The designed way is that you provide a CSS style sheet and have CGI::Widget::Tabs use that. See the class() method for how to do this.

EXAMPLE ^

Before digging into the API and all accessor methods, this example will illustrate how to implement the spotting page from above. So you have something to start with. It will give you enough clues to get on the road quickly. The following code is a simple but complete example. Copy it and run it through the webservers CGI engine. (For a even more complete and useful demo with multiple tabs, see the file tabs-demo.pl in the CGI::Widget::Tabs installation directory.) To fully appreciate it, it would be best to run it in a performance environment, like mod_perl or SpeedyCGI.

    #! /usr/bin/perl -w

    use CGI::Widget::Tabs;
    use CGI;

    print <<EOT;
    Content-Type: text/html;

    <head>
    <style type="text/css">
    table.tab   { border-bottom: solid thin #C0D4E6; text-align: center }
    td.tab      { padding: 2 12 2 12; width: 80; background-color: #FAFAD2 }
    td.tab_actv { padding: 2 12 2 12; width: 80; background-color: #C0D4E6 }
    td.tab_spc  { width: 5 }
    td.tab_ind  { width: 15 }
    </style></head>
    <body>
    EOT

    my $cgi = CGI->new;
    my $tab = CGI::Widget::Tabs->new;
    $tab->cgi_object($cgi);
    $tab->headings( qw/Planes Traines Classics Bikes/ );
    $tab->wrap(3);
    # $tab->wrap(1);    # |uncomment to see the effect of
    # $tab->indent(0);  # |wrapping at 1 without indentation
    $tab->default("Traines");
    $tab->display;
    print "<br>We now should run some intelligent code ";
    print "to process <strong>", $tab->active, "</strong><br>";
    print "</body></html>";

METHODS FOR CGI::Widget::Tabs OBJECTS ^

These methods deal with tab widgets in general. They describe or define the global widget properties and it's behaviour.

new()

Creates and returns a new CGI::Widget::Tabs object. new() does not take any arguments. Example:

    use CGI::Widget::Tabs;
    my $tab = CGI::Widget::Tabs->new;
active()

Returns a string indicating the current active tab heading. This is (in order of precedence) the heading being clicked on, the default heading, or the first in the list. The string value will either be the heading key or the heading text, depending on if you chose to use keys. Example:

    if ( $tab->active() eq "Trains" ) {  # heading text only

    if ( $tab->active() eq "-t" ) {      # key value ISO heading text
cgi_object(OBJECT)

Sets/returns the CGI or CGI::Minimal object. If the optional argument OBJECT is given, the CGI object is set, otherwise it is returned. CGI::Widget::Tabs uses this object internally to process the CGI query parameters. If you want you can use some other CGI object handler. However such an object handler must provide a param() method with corresponding behaviour as do CGI or CGI::Minimal. Note that currently only CGI and CGI::Minimal have been tested. Example:

    # set
    my $cgi = CGI::Minimal->new;
    $tab->cgi_object($cgi);

    # get
    my $cgi = $tab->cgi_object;
cgi_param(STRING)

Sets/returns the CGI query parameter. This parameter identifies the tab in the CGI query string (the funny part of the URL with the ? = & # characters). If the optional argument STRING is given, the query parameter is set. Otherwise it is returned. Usually you can leave this untouched. In that case the default parameter "tab" is used. You will need to set this if you have more CGI query parameters on the URL with "tab" already being taken. Another situation is if you use multiple tab widgets on one page. They both would use "tab" by default causing conflicts. Example:

   # Lets paint a fruit tab and a vegetable tab
   my $fruits_tab = CGI::Widget::Tabs->new;
   my $vegies_tab = CGI::Widget::Tabs->new;

   # this is our link with the outside world
   my $cgi = CGI::Minimal->new;
   $fruits_tab->cgi_object($cgi);
   $vegies_tab->cgi_object($cgi);

   # In the CGI params collection the first is
   # identified by 'ft' and the second by 'vt'
   $fruits_tab->cgi_param("ft");
   $vegies_tab->cgi_param("vt");
class(STRING)

Sets/returns the name of the CSS class used for the tabs markup. If the optional argument STRING is given the class is set, otherwise it is returned. If not set, the widget will be based on the class "tab". In the accompanying style sheet, there are five class elements you need to provide:

1. A table element for containment of the entire tab widget
2. A td element for a normal tab
3. A td element for the active tab
4. A td element for the spacers
5. A td element for the indentation (if needed)

The class names of these elements are directly borrowed from the class() method. The td elements for the active tab, the spacers and the indentations are suffixed with "_actv", "_spc" and "_ind" respectively. For instance, if you'd run

    $tab->class("my_tab");

then the elements look like:

    <table class="my_tab">    # the entire table
    <td class="my_tab">       # normal tab
    <td class="my_tab_actv">  # active tab
    <td class="my_tab_spc">   # spacer
    <td class="my_tab_ind">   # indentation

If you don't wrap headings, then ofcourse you won't need to specify the indentation td's. By the way, the indentation will usually look most natural if it has the same width as the spacers or a multiple thereof. Look at the example in the EXAMPLE section to see how this all works out.

default(STRING)

Overrides which heading is the default. Normally CGI::Widget::Tabs will make the first heading active. Use the default() method if you want to deviate from this. The optional argument STRING must either be the heading key or the heading text, depending on how you chose to initialize the headings. Example:

    # Make the "Trains" heading the default active one.
    $tab->active("Trains");

    # ...or perhaps...
    $tab->active("-t");
display()

Renders the tab widget and prints the resulting HTML to the default output handle (usually STDOUT). Example:

    $tab->display;       # this is the same as...

    print $tab->render;  # ...but saves a few keystrokes

See also the render() method.

heading()

Creates, appends and returns a new heading. The return value will always be an OO heading object. Example:

    my $h = $tab->heading();

In general you will use OO headings if the headings() method is not flexible enough. For trivial applications the headings() method mostly suffices. Look at section PROPERTIES OF OO HEADINGS for more information on OO headings.

headings(LIST)

Sets/returns the tab headings. Without arguments the currently defined headings are returned. If no headings are defined, the empty list is returned. Any returned heading will always be an OO heading, regardless of if and how the initializing LIST argument is used. Look at section PROPERTIES OF OO HEADINGS for more info on how to deal with OO headings.

The optional LIST argument is a short-cut to the OO headings interface. The elements of LIST can take various forms. Let's take a moment to take a close look at the headings of a tab. Tab headings are the things that --from human perspective-- identify a tab page. Observe the spotting example above. Here the different tab pages are identified by the strings "Planes", "Trains", "Classics" and "Bikes". They form the heading for each seperate tab. The LIST elements can be used to preset these tab headings.

An element of LIST can be any one of:

  • a string. E.g.:
        qw/Planes Trains Classics Bikes/

    This is the simplest initializer. In the spotting example the four tabs headings are easily created by feeding these words as a list to the headings() method. And then you are almost done: the headings can be displayed and each heading gets it's own self referencing URL.

  • a key/value pair. E.g.:
        ( -p => "Planes",
          -t => "Trains",
          -c => "Classics,
          -b => "Bikes" )

    For trivial CGI::Widget::Tabs applications, the k/v pairs are the ones you will probably use the most. They come in handy because you don't need to check the value returned by active() against very long words. Even better, if you change the tab headings (upper/lower case, typo's) but use the same keys you don't need to change your code. So it is less error prone. As a pleasant side effect, the URL's get to be significantly shorter. Do notice that the keys want to be unique. Keys in a k/v list are not at all magical. You can choose any string you like with the provision that they start with the '-' (hyphen) sign. The starting '-' of a list entry is what triggers CGI::Widget::Tabs to decide this is a k/v entry. Single or dual character strings tend to be the most convenient keys.

  • a hash

    This use of the headings() method will clutter up your code. The hash tries to mimic and encapsulate all OO accessor methods. If think you need an initializer hash, you probably want OO headings. Use it only if you must. If you can stick with the strings or k/v pairs. That said, the hash keys are the named equivalents of the OO heading properties. E.g.:

        ( { text  => "Planes",
            key   => "p",
            url   => "www.aviation-mag.com",
            class => "heavens_blue",
            raw   => 0 },

You can mix these types in any way you like. The various types will be translated on the fly to OO headings and then processed. Thus you can safely say:

    $tab->headings( "Plaines",
                    -t => "Traines",
                    { text => "Classics",
                      key  => "c",
                      ... } )

Just as the hash initializer, this use does clutter up your code. The reason is that different concepts of information are piled up on one big heep. You will need to scrutinize the code to understand what it is going on. Although it is supported you should refrain yourself from making use of these combinations.

As a summary, here are a three examples of the headings() method for the spotting page.

    # Example 1: Set the headings with a list of strings
    my $tab = CGI::Widget::Tabs->new();
    $tab->headings( qw/Planes Trains Classics Bikes/ );

    # Example 2: Set the headings with a list of k/v pairs
    my $tab = CGI::Widget::Tabs->new();
    $tab->headings( -p => "Planes",
                    -t => "Trains",
                    -c => "Classics,
                    -b => "Bikes" );

    # Example 3: Isolate the "Classics" heading
    my $h = ($tab->headings)[2];

Note that these few statements provide almost enough logic to generate the HTML for the tab widget!

indent(BOOLEAN)

Sets/returns the indentation setting. Without arguments the current setting is returned. indent() specifies if indentation should be added to the next row when the headings get wrapped. indent() is a toggle. By default indent() is set to TRUE. You must explicitely switch it off for the desired effect. The optional argument BOOLEAN can be any argument evaluating to a logical value.

The purpose of swithing off indentation is to simulate a vertical menu. In the spotting example, running

    $tab->wrap(1);
    $tab->indent(0);

would result in something like:

      __________
     |  Planes  |
    --------------
      __________
     |  Trains  |
    --------------
      __________
     | Classics |
    --------------
      __________
     |  Bikes   |
    --------------

You probably need to tweak your style sheet to have it look nicely.

render()

Renders the tab widget and returns the resulting HTML code. This is useful if you need to print the tab to a different file handle. Another use is if you want to manipulate the HTML. For instance to insert session id's or the like. See the class() method and the EXAMPLE section somewhere else in this document to see how you can influence the markup of the tab widget. Example:

    my $html = $tab->render;
    print HTML $html;  # there's a session id filter behind HTML
wrap(NUMBER)

Sets or returns the wrap setting. Without arguments the current wrap setting is returned. If the argument NUMBER is given the headings will wrap to the next row after NUMBER headings. By default headings are not wrapped.

PROPERTIES OF OO HEADINGS ^

These methods define the properties and behaviour of the object oriented headings. Each OO heading can be tailored to specific requirements. Fresh new OO headings are created by using the heading() method on a CGI::Widget::Tabs object. Existing OO headings are returned by the headings() method. In the tabs-demo.pl file OO headings are used as well. So look at that demo for a real life example. Example:

    # create, append and return a new heading
    my $h = $tab->heading();

    # focus on the third heading
    my $h = ($tab->headings)[2];

The properties and behaviour of an OO heading can be set with the following methods:

class(STRING)

Overrides the widget's CSS class for this heading. This is useful if you have a specific heading (e.g. "Maintenance") which always needs it's own private mark up. If the optional argument STRING is given, the class for this heading is set. Otherwise it is retrieved.

key(STRING)

Sets/returns the value to use for this heading in the CGI query param list. This is similar to the use of keys in key/value pairs in the headings() method. The goal is to simplify programming logic and shorten the URL's. (See the headings() method elsewhere in this document for further explanation). Example:

    # display the full heading...
    # ...but use a small key as query param value
    $h->text("Remote Configurations");
    $h->key("rc");

In contrast to the use of key/value pairs, CGI::Widget::Tabs knows that this is a key and not a value. After all, you are using the key() method, right? Consequently you don't need the prepend the key with a hyphen ("-"). You may consider using a hyphen for your keys nevertheless. It will lead to more transparent code. Observe how the snippet from above with a prepended "-" will later on result in the following check:

    if ( $tab->active eq "-rc" ) {  # clearly we are using keys ....

Consider this a mild suggestion.

raw(BOOLEAN)

The heading text will normally be HTML encoded. If you wish you can use hard coded HTML. To avoid escaping this HTML, you need to set raw() to a logical TRUE. This is usually a 1 (one). Setting it to FALSE (usually a 0) will re-enable HTML encoding. The optional argument BOOLEAN can be any argument evaluating to a logical value. Setting raw() will not take effect until the widget is rendered. So it does not matter when you set it, as long as you haven't rendered the widget. Examples:

    # HTML encoded
    $h1->text("Names A > L");
    $h2->text("Names M < Z");

    # Raw
    $h1->text("Names A &gt; L");
    $h1->raw(1);

    $h2->text("Names M &lt; Z");
    $h2->raw(1);

    # get the encoding setting of the fourth element
    my $h = ($tab->headings)[3];
    my $raw = $h->raw;
text(STRING)

Sets/returns the heading text. If the optional argument STRING is given, the text will be set otherwise it will be returned. The heading text will be HTML encoded unless explicitely told otherwise (see: raw()). Examples:

    # set heading text for the first two headings
    ($tab->headings)[0]->text("Names A > L");
    ($tab->headings)[1]->text("Names M < Z");

    # get the text of the 4th heading
    my $text = ($tab->headings)[3]->text;
url(STRING)

Overrides the self referencing URL for this heading. If the optional argument STRING is given the URL is set. Otherwise it is returned. The URL is used exactly as given. This means that any query params and values need to be added explicitely. If a URL is not set, the heading will get a default self referencing URL. For trivial applications, you will mostly be using this one. Note that generating the self referencing URL will be delayed until the tab widget it rendered. This means it will not be returned by the url() method. Example:

      $h->url("www.someremotesite.com");  # go somewhere else

      my $url = $h->url;                  # return the URL

BUGS ^

As a side effect, the CGI query parameter to identify the tab (see the cgi_param() method) is always moved to the end of the query string.

CONTRIBUTIONS ^

I would appreciate receiving your CSS style sheets used for the tabs markup. Especially if you happened to be professionally concerned with markup and layout. For techies like us it is not always easy to see what goes and what doesn't. If you send in a nice one, I will gladly bundle it with the next release.

ACKNOWLEDGEMENTS ^

Bodo Eing <eingb@uni-muenster.de>
Sagar Shah <sagarshah@softhome.net>
Bernie Ledwick <bl@man.fwltech.com>
Bernhard Schmalhofer <Bernhard.Schmalhofer@biomax.de>

AUTHOR ^

Koos Pol <koos_pol@raketnet.nl>

DOWNLOAD ^

The latest version of CGI::Widget::Tabs is available from CPAN (http://cpan.perl.org) or the CGI::Widget::Tabs homepage (http://users.raketnet.nl/koos_pol/en/Tabs/index.html)

SEE ALSO ^

the manpages for CGI or CGI::Minimal, the CSS1 specs from the World Wide Web consortium (http://www.w3.org/TR/REC-CSS1)

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