#============================================================= -*-perl-*-
#
# Template::Manual::Filters
#
# DESCRIPTION
#   This section lists all the standard filters distributed with the
#   Template Toolkit for post-processing output.
#
# AUTHOR
#   Andy Wardley  <abw@andywardley.com>
#
# COPYRIGHT
#   Copyright (C) 1996-2001 Andy Wardley.  All Rights Reserved.
#   Copyright (C) 1998-2001 Canon Research Centre Europe Ltd.
#
#   This module is free software; you can redistribute it and/or
#   modify it under the same terms as Perl itself.
#
# REVISION
#   
#
#========================================================================


#------------------------------------------------------------------------
# IMPORTANT NOTE
#   This documentation is generated automatically from source
#   templates.  Any changes you make here may be lost.
# 
#   The 'docsrc' documentation source bundle is available for download
#   from http://www.template-toolkit.org/docs.html and contains all
#   the source templates, XML files, scripts, etc., from which the
#   documentation for the Template Toolkit is built.
#------------------------------------------------------------------------

=head1 NAME

Template::Manual::Filters - Standard filters

=head1 DESCRIPTION

This section lists all the standard filters distributed with the
Template Toolkit for post-processing output.

=head1 STANDARD FILTERS



=head2 format(format)

The 'format' filter takes a format string as a parameter (as per
printf()) and formats each line of text accordingly.

    [% FILTER format('<!-- %-40s -->') %]
    This is a block of text filtered 
    through the above format.
    [% END %]

output:

    <!-- This is a block of text filtered        -->
    <!-- through the above format.               -->

=head2 upper

Folds the input to UPPER CASE.

    [% "hello world" FILTER upper %]

output:

    HELLO WORLD

=head2 lower

Folds the input to lower case.

    [% "Hello World" FILTER lower %]

output:

    hello world

=head2 ucfirst

Folds the first character of the input to UPPER CASE.

    [% "hello" FILTER ucfirst %]

output:

    Hello

=head2 lcfirst

Folds the first character of the input to lower case.

    [% "HELLO" FILTER lcfirst %]

output:

    hELLO

=head2 trim

Trims any leading or trailing whitespace from the input text.  Particularly 
useful in conjunction with INCLUDE, PROCESS, etc., having the same effect
as the TRIM configuration option.

    [% INCLUDE myfile | trim %]

=head2 collapse

Collapse any whitespace sequences in the input text into a single space.
Leading and trailing whitespace (which would be reduced to a single space)
is removed, as per trim.

    [% FILTER collapse %]

       The   cat

       sat    on

       the   mat

    [% END %]

output:

    The cat sat on the mat

=head2 html

Converts the characters 'E<lt>', 'E<gt>' and '&' to '&lt;', '&gt;' and
'&amp;', respectively, protecting them from being interpreted as
representing HTML tags or entities.

    [% FILTER html %]
    Binary "<=>" returns -1, 0, or 1 depending on...
    [% END %]

output:

    Binary "&lt;=&gt;" returns -1, 0, or 1 depending on...

=head2 html_entity

The html filter is fast and simple but it doesn't encode the full
range of HTML entities that your text may contain.  The html_entity
filter uses either the Apache::Util module (which is written in C and
is therefore faster) or the HTML::Entities module (written in Perl but
equally as comprehensive) to perform the encoding.  If one or other of
these modules are installed on your system then the text will be
encoded (via the escape_html() or encode_entities() subroutines
respectively) to convert all extended characters into their
appropriate HTML entities (e.g. converting 'é' to '&eacute;').  If
neither module is available on your system then an 'html_all' exception
will be thrown reporting an appropriate message.   

For further information on HTML entity encoding, see
http://www.w3.org/TR/REC-html40/sgml/entities.html.

=head2 html_para

This filter formats a block of text into HTML paragraphs.  A sequence of 
two or more newlines is used as the delimiter for paragraphs which are 
then wrapped in HTML E<lt>pE<gt>...E<lt>/pE<gt> tags.

    [% FILTER html_para %]
    The cat sat on the mat.

    Mary had a little lamb.
    [% END %]

output:

    <p>
    The cat sat on the mat.
    </p>

    <p>
    Mary had a little lamb.
    </p>

=head2 html_break

Similar to the html_para filter described above, but uses the HTML tag
sequence E<lt>brE<gt>E<lt>brE<gt> to join paragraphs.

    [% FILTER html_break %]
    The cat sat on the mat.

    Mary had a little lamb.
    [% END %]

output:

    The cat sat on the mat.
    <br>
    <br>
    Mary had a little lamb.

=head2 uri

This filter URI escapes the input text, converting any characters 
outside of the permitted URI character set (as defined by RFC 2396)
into a C<%nn> hex escape.

    [% 'my file.html' | uri %]

output:

    my%20file.html

Note that URI escaping isn't always enough when generating hyperlinks in
an HTML document.  The C<&> character, for example, is valid in a URI and
will not be escaped by the URI filter.  In this case you should also filter
the text through the 'html' filter.

    <a href="[% filename | uri | html %]">click here</a>

=head2 indent(pad)

Indents the text block by a fixed pad string or width.  The 'pad' argument
can be specified as a string, or as a numerical value to indicate a pad
width (spaces).  Defaults to 4 spaces if unspecified.

    [% FILTER indent('ME> ') %]
    blah blah blah
    cabbages, rhubard, onions
    [% END %]

output:

    ME> blah blah blah
    ME> cabbages, rhubard, onions

=head2 truncate(length)

Truncates the text block to the length specified, or a default length of
32.  Truncated text will be terminated with '...' (i.e. the '...' falls
inside the required length, rather than appending to it).

    [% FILTER truncate(21) %]
    I have much to say on this matter that has previously 
    been said on more than one occasion.
    [% END %]

output:

    I have much to say...

=head2 repeat(iterations)

Repeats the text block for as many iterations as are specified (default: 1).

    [% FILTER repeat(3) %]
    We want more beer and we want more beer,
    [% END %]
    We are the more beer wanters!

output:

    We want more beer and we want more beer,
    We want more beer and we want more beer,
    We want more beer and we want more beer,
    We are the more beer wanters!

=head2 remove(string) 

Searches the input text for any occurrences of the specified string and 
removes them.  A Perl regular expression may be specified as the search 
string.

    [% "The  cat  sat  on  the  mat" FILTER remove('\s+') %]

output: 

    Thecatsatonthemat

=head2 replace(search, replace) 

Similar to the remove filter described above, but taking a second parameter
which is used as a replacement string for instances of the search string.

    [% "The  cat  sat  on  the  mat" | replace('\s+', '_') %]

output: 

    The_cat_sat_on_the_mat

=head2 redirect(file)

The 'redirect' filter redirects the output of the block into a separate
file, specified relative to the OUTPUT_PATH configuration item.

    [% FOREACH user = myorg.userlist %]
       [% FILTER redirect("users/${user.id}.html") %]
          [% INCLUDE userinfo %]
       [% END %]
    [% END %]

or more succinctly, using side-effect notation:

    [% INCLUDE userinfo 
         FILTER redirect("users/${user.id}.html")
	   FOREACH user = myorg.userlist 
    %]

A 'file' exception will be thrown if the OUTPUT_PATH option is undefined.

=head2 eval(template_text)

The 'eval' filter evaluates the block as template text, processing
any directives embedded within it.  This allows template variables to
contain template fragments, or for some method to be provided for
returning template fragments from an external source such as a
database, which can then be processed in the template as required.

    my $vars  = {
	fragment => "The cat sat on the [% place %]",
    };
    $template->process($file, $vars);

The following example:

    [% fragment | eval %]

is therefore equivalent to 

    The cat sat on the [% place %]

The 'evaltt' filter is provided as an alias for 'eval'.

=head2 perl(perlcode)

The 'perl' filter evaluates the block as Perl code.  The EVAL_PERL
option must be set to a true value or a 'perl' exception will be
thrown.

    [% my_perl_code | perl %]

In most cases, the [% PERL %] ... [% END %] block should suffice for 
evaluating Perl code, given that template directives are processed 
before being evaluate as Perl.  Thus, the previous example could have
been written in the more verbose form:

    [% PERL %]
    [% my_perl_code %]
    [% END %]

as well as

    [% FILTER perl %]
    [% my_perl_code %]
    [% END %]

The 'evalperl' filter is provided as an alias for 'perl' for backwards
compatibility.

=head2 stdout(binmode)

The stdout filter prints the output generated by the enclosing block to
STDOUT.  If binmode is set, binary mode on STDOUT is turned on (see the
binmode perl function.

The stdout filter can be used to force binmode on STDOUT, or also inside
redirect, null or stderr blocks to make sure that particular output goes
to stdout. See the null filter below for an example.

=head2 stderr

The stderr filter prints the output generated by the enclosing block to
STDERR.

=head2 null

The null filter prints nothing.  This is useful for plugins whose
methods return values that you don't want to appear in the output.
Rather than assigning every plugin method call to a dummy variable
to silence it, you can wrap the block in a null filter:

    [% FILTER null;
        USE im = GD.Image(100,100);
        black = im.colorAllocate(0,   0, 0);
        red   = im.colorAllocate(255,0,  0);
        blue  = im.colorAllocate(0,  0,  255);
        im.arc(50,50,95,75,0,360,blue);
        im.fill(50,50,red);
        im.png | stdout(1);
       END;
    -%]

Notice the use of the stdout filter to ensure that a particular expression
generates output to stdout (in this case in binary mode).

=head2 latex(outputType)

Passes the text block to LaTeX and produces either PDF, DVI or
PostScript output.  The 'outputType' argument determines the output
format and it should be set to one of the strings: "pdf" (default),
"dvi", or "ps".

The text block should be a complete LaTeX source file.

    [% FILTER latex("pdf") -%]
    \documentclass{article}

    \begin{document}

    \title{A Sample TT2 \LaTeX\ Source File}
    \author{Craig Barratt}
    \maketitle

    \section{Introduction}
    This is some text.

    \end{document}
    [% END -%]

The output will be a PDF file. You should be careful not to prepend or
append any extraneous characters or text outside the FILTER block,
since this text will wrap the (binary) output of the latex filter.
Notice the END directive uses '-%]' for the END_TAG to remove the
trailing new line.

One example where you might prepend text is in a CGI script where
you might include the Content-Type before the latex output, eg:

    Content-Type: application/pdf

    [% FILTER latex("pdf") -%]
    \documentclass{article}
    \begin{document}
    ...
    \end{document}
    [% END -%]

In other cases you might use the redirect filter to put the output
into a file, rather than delivering it to stdout.  This might be
suitable for batch scripts:

    [% output = FILTER latex("pdf") -%]
    \documentclass{article}
    \begin{document}
    ...
    \end{document}
    [% END; output | redirect("document.pdf", 1) -%]

(Notice the second argument to redirect to force binary mode.)

Note that the latex filter runs one or two external programs, so it
isn't very fast.  But for modest documents the performance is adequate,
even for interactive applications.

A error of type 'latex' will be thrown if there is an error reported
by latex, pdflatex or dvips.

=head1 AUTHOR

Andy Wardley E<lt>abw@andywardley.comE<gt>

L<http://www.andywardley.com/|http://www.andywardley.com/>




=head1 VERSION

Template Toolkit version 2.08, released on 30 July 2002.

=head1 COPYRIGHT

  Copyright (C) 1996-2002 Andy Wardley.  All Rights Reserved.
  Copyright (C) 1998-2002 Canon Research Centre Europe Ltd.

This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

