CGI::Push - Simple Interface to Server Push

SYNOPSIS

           use CGI::Push qw(:standard);

           do_push(-next_page=>\&next_page,
                   -last_page=>\&last_page,
                   -delay=>0.5);

           sub next_page {
               my($q,$counter) = @_;
               return undef if $counter >= 10;
               return start_html('Test'),
                      h1('Visible'),"\n",
                      "This page has been called ", strong($counter)," times",
                      end_html();
             }

            sub last_page {
                my($q,$counter) = @_;
                return start_html('Done'),
                       h1('Finished'),
                       strong($counter),' iterations.',
                       end_html;
            }

DESCRIPTION

       CGI::Push is a subclass of the CGI object created by
       CGI.pm.  It is specialized for server push operations,
       which allow you to create animated pages whose content
       changes at regular intervals.

       You provide CGI::Push with a pointer to a subroutine that
       will draw one page.  Every time your subroutine is called,
       it generates a new page.  The contents of the page will be
       transmitted to the browser in such a way that it will
       replace what was there beforehand.  The technique will
       work with HTML pages as well as with graphics files,
       allowing you to create animated GIFs.

USING CGI::Push

       CGI::Push adds one new method to the standard CGI suite,
       do_push().  When you call this method, you pass it a
       reference to a subroutine that is responsible for drawing
       each new page, an interval delay, and an optional
       subroutine for drawing the last page.  Other optional
       parameters include most of those recognized by the CGI
       header() method.

       You may call do_push() in the object oriented manner or
       not, as you prefer:
           $q = new CGI::Push;
           $q->do_push(-next_page=>\&draw_a_page);

               -or-

           use CGI::Push qw(:standard);
           do_push(-next_page=>\&draw_a_page);

       Parameters are as follows:

           do_push(-next_page=>\&my_draw_routine);

       This required parameter points to a reference to a
       subroutine responsible for drawing each new page.  The
       subroutine should expect two parameters consisting of the
       CGI object and a counter indicating the number of times
       the subroutine has been called.  It should return the
       contents of the page as an array of one or more items to
       print.  It can return a false value (or an empty array) in
       order to abort the redrawing loop and print out the final
       page (if any)

           sub my_draw_routine {
               my($q,$counter) = @_;
               return undef if $counter > 100;
               return start_html('testing'),
                      h1('testing'),
                      "This page called $counter times";
           }


       -last_page
           This optional parameter points to a reference to the
           subroutine responsible for drawing the last page of
           the series.  It is called after the -next_page routine
           returns a false value.  The subroutine itself should
           have exactly the same calling conventions as the
           -next_page routine.

       -type
           This optional parameter indicates the content type of
           each page.  It defaults to "text/html".  Currently,
           server push of heterogeneous document types is not
           supported.

       -delay
           This indicates the delay, in seconds, between frames.
           Smaller delays refresh the page faster.  Fractional
           values are allowed.

           If not specified, -delay will default to 1 second

           These have the same meaning as the like-named
           parameters in CGI::header().

INSTALLING CGI::Push SCRIPTS

       Server push scripts must be installed as no-parsed-header
       (NPH) scripts in order to work correctly.  On Unix
       systems, this is most often accomplished by prefixing the
       script's name with "nph-".  Recognition of NPH scripts
       happens automatically with WebSTAR and Microsoft IIS.
       Users of other servers should see their documentation for
       help.

CAVEATS

       This is a new module.  It hasn't been extensively tested.

AUTHOR INFORMATION

       be used and modified freely, but I do request that this
       copyright notice remain attached to the file.  You may
       modify this module as you wish, but if you redistribute a
       modified version, please attach a note listing the
       modifications you have made.

       Address bug reports and comments to:
       lstein@genome.wi.mit.edu

BUGS

       This section intentionally left blank.

SEE ALSO

       the CGI::Carp manpage, the CGI manpage

       =cut