CGI::ProgressBar(3)

NAME
CGI::ProgressBar - CGI.pm sub-class with a progress bar object

SYNOPSIS
        use strict;
        use warnings;
        use CGI::ProgressBar qw/:standard/;
        $| = 1; # Do not buffer output
        print header,
                start_html(
                        -title=>'A Simple Example',
                        -style=>{
                                -src  => '', # You can override the bar style here
                                -code => '', # or inline, here.
                        }
                ),
                h1('A Simple Example'),
                p('This example will update a JS/CSS progress bar.'),
                progress_bar( -from=>1, -to=>100 );
        # We're set to go.
        for (1..10){
                print update_progress_bar;
                # Simulate being busy:
                sleep 1;
        }
        # Now we're done, get rid of the bar:
        print hide_progress_bar;
        print p('All done.');
        print end_html;
        exit;

DESCRIPTION
This module provides an HTML/JS progress bar for web browsers, to keep end-users occupied when otherwise nothing would appear to be happening.

It aims to require that the recipient client have a minimum of JavaScript 1.0, HTML 4.0, and CSS/1.

All feedback would be most welcome. Address at the end of the POD.

  DEPENDENCIES
        CGI

  EXPORT
        progress_bar
        update_progress_bar
        hide_progress_bar

USE
The module sub-classes CGI.pm, providing three additional methods (or functions, depending on your taste), each of which are detailed below.

Simply replace your "use CGI qw//;" with "use CGI::ProgressBar qw//;".

Make sure you are aware of your output buffer size: "$|=$smothingsmall".

Treat each new function as any other CGI.pm HTML-producing routine with the exception that the arguments should be supplied as in OOP form. In other words, the following are all the same:

        my $html = $query->progress_bar;
        my $html = progress_bar;
        my $html = progress_bar(from=>1, to=>10);
        my $html = $query->progress_bar(from=>1, to=>10);
        my $html = $query->progress_bar(-to=>10);

This will probably change if someone would like it to.

FUNCTIONS/METHODS

  FUNCTION/METHOD progress_bar
Returns mark-up that instantiates a progress bar. Currently that is HTML and JS, but perhaps the JS ought to go into the head.

The progress bar itself is an object in this class, stored in the calling ("CGI") object - specifically in the field "progress_bar", which we create. (TODO: Make this field an array to allow multiple bars per page.)

from
to  Values which the progress bar spans. Defaults: 0, 100.

orientation
    If set to "vertical" displays the bar as a strip down the screen; otherwise, places it across the screen.

width
height
    The width and height of the progress bar, in pixels. Cannot accept percentages (yet). Defaults: 400, 20, unless you specify "orientation" as "vertical", in which case this is reversed.

blocks
    The number of blocks to appear in the progress bar. Default: 10. You probably want to link this to "from" and "to" or better still, leave it well alone: it may have been a mistake to even include it. "steps" is an alias for this attribute.

label
    Supply this parameter with a true value to have a numerical display of progress. Default is not to display it.

layer_id
    Most HTML elements on the page have "id" attributes. These can be accessed through the "layer_id" field, which is a hash with the follwoing keys relating to the "id" value:

mycss
    Custom CSS to be written inline (ugh) after any system CSS.

    form
        The "form" which contains everything we display.

    container
        The "div" containing everything we display.

    block
        This value is used as a prefixed for the "id" of each block of the bar, with the suffix being a number incremented from 1.

    number
        The digits being updated as the bar progresses, if the option is enabled.

  FUNCTION/METHOD update_progress_bar
Updates the progress bar.

  FUNCTION/METHOD hide_progress_bar
Hides the progress bar.

CSS STYLE CLASS EMPLOYED
You can add CSS to be output into the page body (ugh) in the "mycss" field. Bear in mind that the width and height settings are programatically assigned.

pblib_bar
    A "DIV" containing the whole progress bar, including any accessories (such as the label). The only attribute used by this module is "width", which is set dynamically. The rest is up to you. A good start is:

            padding:    2 px;
            border:     solid black 1px;
            text-align: center;

pblib_block_off, pblib_block_on
    An individual block within the status bar. The following attributes are set dynamically: "width", "height", "margin-right".

pblib_number
    Formatting for the "label" text (part of which is actually an "input type='text'" element. "border" and "text-align" are used here, and the whole appears centred within a "table".

BUGS, CAVEATS, TODO

One bar per page
    This may change.

Parameter passing doesn't match CGI.pm
    But it will in the next release if you ask me for it.

"colors" not implimented
    I'd like to see here something like the "Tk::ProgressBar::colors"; not because I've ever used it, but because it might be cool.

Horizontal orientation only
    You can get around this by adjusting the CSS, but you'd rather not. And even if you did, the use of "-label" might not look very nice unless you did something quite fancy. So the next version (or so) will support an "-orientation" option.

Inline CSS and JS
    Because it's easiest for me. I suppose some kind of over-loading of the "CGI::start_html" would be possible, but then I'd have to check it, and maybe update it, every time CGI.pm was updated, which I don't fancy.

CGI UPLOAD HOOK
I'm not convinced it works yet, even in CGI.pm verion 3.15.

If anyone knows otherwise, please mail me: I have spent an hour on the below, and it seems that the hook is called more times than necessary....

  PROCESS
The script has to both upload and process a file.

The hook script is called when the object is constructed, thus before any headers can be output. There the hook needs to output its own headers, and we only output headers for the 'select file' page when the hook has not been called.

The first tiem the hook is called, then, it outputs HTTP headers and begins the page. This is fine.

The next time it is called, it outputs the JS call to update the progress bar. This is fine.

The problem is that the hook seems to be called many more times than necessary.

  SOURCE
        #!/usr/local/bin/perl
        use warnings;
        use strict;

        use CGI::ProgressBar qw/:standard/;
        $| = 1; # Do not buffer output

        my $data;
        my $hook_called;
        my $cgi = CGI->new(\&bar_hook, $data);

        if (not $hook_called){
                print $cgi->header,
                $cgi->start_html( -title=>'A Simple Example', ),
                $cgi->h1('Simple Upload-hook Example');
        }

        print $cgi->start_form( -enctype=>'application/x-www-form-urlencoded'),
                $cgi->filefield( 'uploaded_file'),
                $cgi->submit,
                $cgi->end_form,p;

        if ($cgi->param('uploaded_file')){
                print 'uploaded_file: '.param('uploaded_file');
        }

        sub bar_hook {
                my ($filename, $buffer, $bytes, $data) = @_;
                if (not $hook_called){
                        print header,
                        start_html( -title=>'Simple Upload-hook Example', ),
                        h1('Uploading'),
                        p(
                                "Have to read <var>$ENV{CONTENT_LENGTH}</var> in blocks of <var>$bytes</var>, total blocks should be ",
                                ($ENV{CONTENT_LENGTH}/$bytes)
                        ),
                        progress_bar( -from=>1, -to=>($ENV{CONTENT_LENGTH}/$bytes), -debug=>1 );
                        $hook_called = 1;
                } else {
                        # Called every $bytes, I would have thought.
                        # But calls seem to go on much longer than $ENV{CONTENT_LENGTH} led me to believe they ought:
                        print update_progress_bar;
                        print "$ENV{CONTENT_LENGTH} ... $total_bytes ... $hook_called ... div="
                        .($hook_called/$total_bytes)
                        ."<br>"
                }
                sleep 1;
                $hook_called += $total_bytes;
        }

        print $cgi->hide_progress_bar;
        if ($hook_called){
                print p('All done after '.$hook_called.' calls');
        }
        print $cgi->end_html;
        exit;

AUTHOR
Lee Goddard "lgoddard -in- cpan -dat- org", "cpan -ut- leegoddard -dut- net"

  COPYRIGHT
Copyright (C) Lee Goddard, 2002, 2003, 2005. All Rights Reserved. This software is made available under the same terms as Perl itself. You may use and redistribute this software under the same terms as Perl itself.

KEYWORDS
HTML, CGI, progress bar, widget

SEE ALSO
perl. CGI, Tk::ProgressBar,

MODIFICATIONS
25 March 2004: Updated the POD.^

16 December 2005: Updated the styles and POD. Removed gap attribute.

16 December 2005: Updated the default styles.

30 November 2010: Updated with patch from tlhackque - thank you.

POD ERRORS
Hey! The above document had some coding errors, which are explained below:

Around line 276:
    '=item' outside of any '=over'

Around line 391:
    You forgot a '=back' before '=head1'

Around line 427:
    You forgot a '=back' before '=head1'

Around line 453:
    =back without =over