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;
}
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.
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:
use CGI::Push;
$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 $counter times";
}
You are of course free to refer to create and use global variables within your draw routine in order to achieve special effects.
If not specified, -delay will default to 1 second
do_push() -type parameter, you can specify the MIME type of
each page on a case-by-case basis.
If you use this option, you will be responsible for producing the HTTP header for each page. Simply modify your draw routine to look like this:
sub my_draw_routine {
my($q,$counter) = @_;
return header('text/html'), # note we're producing the header here
start_html('testing'),
h1('testing'),
"This page called $counter times";
}
You can add any header fields that you like, but some (cookies and status
fields included) may not be interpreted by the browser. One interesting
effect is to display a series of pages, then, after the last page, to
redirect the browser to a new URL. Because redirect() does
b<not> work, the easiest way is with a -refresh header field, as
shown below:
sub my_draw_routine {
my($q,$counter) = @_;
return undef if $counter > 10;
return header('text/html'), # note we're producing the header here
start_html('testing'),
h1('testing'),
"This page called $counter times";
}
sub my_last_page {
header(-refresh=>'5; URL=http://somewhere.else/finished.html',
-type=>'text/html'),
start_html('Moved'),
h1('This is the last page'),
'Goodbye!'
hr,
end_html;
}
push_delay() from within your draw routine.
push_delay() takes a single numeric argument representing the
number of seconds you wish to delay after the current page is displayed and
before displaying the next one. The delay may be fractional. Without
parameters, push_delay() just returns the current delay.
Address bug reports and comments to: lstein@genome.wi.mit.edu