=head1 NAME

HTML::Mason::Interp - Mason Component Interpreter

=head1 SYNOPSIS

    my $i = new HTML::Mason::Interp (data_dir=>'/usr/local/mason',
                                     comp_root=>'/usr/local/www/htdocs/',
                                     < other params >);

=head1 DESCRIPTION

Interp is the Mason workhorse, executing components and routing their
output and errors to all the right places. In a mod_perl environment,
Interp objects are handed off immediately to an ApacheHandler object
which internally calls the Interp implementation methods. In that case
the only user method is the new() constructor.

If you want to call components outside of mod_perl (e.g. from CGI or a
stand-alone Perl script), see the L<STANDALONE MODE> section below.

=head1 PARAMETERS FOR new() CONSTRUCTOR

=over

=item comp_root

A required argument, this specifies the root of your component source
tree.

=item current_time

Overrides the time and date returned by mc_time and mc_date with a
fixed value. This is useful for testing time-based components,
e.g. seeing what a page will look like tomorrow. The argument is a
Perl time() value (seconds since the epoch).

With no current_time parameter (the default), mc_time and mc_date
report the true time.

=item data_dir

The other required argument. Mason's various data directories (obj, cache,
debug, etc), live within the data_dir.

=item max_recurse

The maximum component stack depth the interpreter is allowed to
descend before signalling an error.  Default is 16.

=item out_method

Indicates where to send output. If out_method is a reference to a
scalar, output is appended to the scalar.  If out_method is a
reference to a subroutine, the subroutine is called with each output
string. For example, to send output to a file called "mason.out":

    my $fh = new IO::File ">mason.out";
    ...
    out_method => sub { $fh->print($_[0]) }

In standalone mode, out_method prints to standard output. In a web
environment, out_method defaults to using C<$r->print>.

=item parser

Parser object for compiling components on the fly. If omitted, creates
a parser with default parameters.

=item preloads

A set of component paths and/or component directories to load when the
interpreter initializes. This should only be used for components that
are frequently viewed and rarely updated.  See the L<Admin/preloading>
section of the I<Admin Guide> for further details.

=item static_file_root

Absolute path to prepend to relative filenames passed to C<mc_file()>. Does
not require a trailing slash. For example, if the file root is
'/foo/bar', then C<mc_file('baz/bap')> will read the file
'/foo/bar/baz/bap'.

=item system_log_file

Absolute path of system log.  Default is data_dir/etc/system.log.

=item system_log_separator

Separator to use between fields on a line in the system log. Default is ctrl-A ("\cA").

=item system_log_events

A string value indicating one or more events to record in the system
log, separated by "|". Default is to log nothing.

=item use_data_cache

True or undef, default is true. You may need to disable data caching
temporarily for debugging purposes, but normally this should be left
alone.

=item use_object_files

True or undef, default is true.  Specifies whether Mason creates
object files to save the results of component parsing. You may want to
turn off object files for disk space reasons, but otherwise this
should be left alone.

=item use_reload_file

True or undef, default is undef. If true, disables Mason's automatic
timestamp checking on component source files, relying instead on an
explicitly updated L<Admin/reload file>.

=item verbose_compile_error

True or undef, default is undef. If true, component compile errors are
followed with the full component source, annotated with line numbers,
to better interpret the error message. Does not affect runtime errors.

=back

=head1 STANDALONE MODE

Although Mason is most commonly used in conjunction with mod_perl,
there is also a functional API that allows you to use Mason from CGI
programs or from stand-alone Perl scripts.  In the latter case Mason can be
used as a glorified Text::Template, producing a set of
files from components, or used to generate a flat version of a componentized site.

When using Mason outside of mod_perl, just create a Parser and Interp
object; you do not need the ApacheHandler object.  Once you've created
an interpreter, the main thing you'll want to do with it is call a
component and do something with the output. To call a component, use
Interp's exec() method:

    $interp->exec(<compPath> [,<..list of component params..>]);

Component parameters are given as a series of name/value pairs, just
as they are with C<mc_comp>. exec returns the return value of
the component. Component output is sent to standard output by default,
but you can change this by specifying C<out_method>. Here is a skeleton
script that calls a component and places the output in a file:

    my $outbuf;
    my $parser = new HTML::Mason::Parser;
    my $interp = new HTML::Mason::Interp (parser=>$parser,
					  comp_root=>'<component root>',
					  data_dir=>'<data directory>',
					  out_method=>\$outbuf);
    my $retval = $interp->exec('<component path>',<args>...);
    open(F,"mason.out");
    print F $outbuf;
    close(F);
    print "return value of component was: $retval\n";

=head1 AUTHOR

Jonathan Swartz, swartz@transbay.net

=head1 SEE ALSO

L<HTML::Mason>,
L<HTML::Mason::Parser>,
L<HTML::Mason::ApacheHandler>,
L<HTML::Mason::Admin>

=cut
