use strict; use warnings; 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 $counter >= 10; .... } sub last_page { my($q,$counter) = @_; return ... }
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.
Only Netscape Navigator supports server push. Internet Explorer browsers do not.
You may call do_push() in the object oriented manner or not, as you prefer:
use CGI::Push; $q = CGI::Push->new; $q->do_push(-next_page=>\&draw_a_page); -or- use CGI::Push qw(:standard); do_push(-next_page=>\&draw_a_page);
Parameters are as follows:
do_push(-next_page=>\&my_draw_routine);
This required parameter points to a reference to a subroutine responsible for drawing each new page. The subroutine should expect two parameters consisting of the CGI object and a counter indicating the number of times the subroutine has been called. It should return the contents of the page as an array of one or more items to print. It can return a false value (or an empty array) in order to abort the redrawing loop and print out the final page (if any)
sub my_draw_routine { my($q,$counter) = @_; return undef if $counter > 100; ... }
You are of course free to refer to create and use global variables within your draw routine in order to achieve special effects.
If not specified, -delay will default to 1 second
If not specified, -nph will default to 1 (as needed for many servers, see below).
If you use this option, you will be responsible for producing the HTTP header for each page. Simply modify your draw routine to look like this:
sub my_draw_routine { my($q,$counter) = @_; return header('text/html'), # note we're producing the header here .... }
You can add any header fields that you like, but some (cookies and status fields included) may not be interpreted by the browser. One interesting effect is to display a series of pages, then, after the last page, to redirect the browser to a new URL. Because redirect() does b<not> work, the easiest way is with a -refresh header field, as shown below:
sub my_draw_routine { my($q,$counter) = @_; return undef if $counter > 10; return header('text/html'), # note we're producing the header here ... } sub my_last_page { return header(-refresh=>'5; URL=http://somewhere.else/finished.html', -type=>'text/html'), ... }
Apache web server from version 1.3b2 on does not need server push scripts installed as NPH scripts: the -nph parameter to do_push() may be set to a false value to disable the extra headers needed by an NPH script.
Address bug reports and comments to: https://github.com/leejo/CGI.pm/issues
The original bug tracker can be found at: https://rt.cpan.org/Public/Dist/Display.html?Queue=CGI.pm
When sending bug reports, please provide the version of CGI.pm, the version of Perl, the name and version of your Web server, and the name and version of the operating system you are using. If the problem is even remotely browser dependent, please provide information about the affected browsers as well. Copyright 1995-1998, Lincoln D. Stein. All rights reserved.