=for rcs $Id: Printer.pod,v 1.4 2002/09/25 13:31:21 dk Exp $

=head1 NAME

Prima::Printer - system printing services

=head1 DESCRIPTION

I<Prima::Printer> is a descendant of I<Prima::Drawable> class.
It provides access to the system printing services, where
available. If the system provides no graphics printing,
the default PostScript (tm) interface module I<Prima::PS::Printer>
is used instead.

=head1 Usage

I<Prima::Printer> objects are never created directly. During the life
of a program, there exists only one instance of a printer 
object, created automatically by I<Prima::Application>.
I<Prima::Printer> object is created only when the system provides
graphic printing capabilities - drawing and painting procedures 
on a graphic device.
If there are no such API, I<Prima::Application> creates an
instance of I<Prima::PS::Printer> instead, which emulates
a graphic device, producing PostScript output.
The discretion between I<Prima::Printer> and I<Prima::PS::Printer>
is transparent for both the user and the programmer, unless 
printer device specific adjustments desired.

A printing session is started by C<begin_doc()>, which switches
the object into the painting state. If finished by C<end_doc()>,
the document is delivered to a printer device. Alternative finishing
method, C<abort_doc()>, terminates the printing session with
no information printed, unless the document is multi-paged
and pages were sent to the printer via C<new_page()>.

A printer object ( that means, both I<Prima::Printer> and I<Prima::PS::Printer> )
provides selection of the printer mechanism. C<printers()> method
returns array of hashes, each describing a printer device; C<get_default_printer()>
returns a default printer string identifier. A printer device can be selected
via the C<::printer> property.

The capabilites of the selected printer can be adjusted via C<setup_dialog()>
method, that invokes a system-provided ( or, in case of I<Prima::PS::Printer>,
toolkit-provided ) printer setup dialog, so the user can adjust settings of a
printer device.
It depends on the system, whether the setup changes only the instance settings, or
the default behavior of a printer driver is affected for all programs.

Some printer capabilities can be queried by the C<::size()> property,
that reports the dimension of the page, the C<::resolution()> property,
that reports the DPI resolution selected by a printer driver and
font list ( by C<fonts()> method ), available for usage.

Typical code that prints the document looks like

   my $p = $::application-> get_printer;
   if ( $p-> begin_doc) {
      ... draw ...
      $p-> end_doc;
   }

In addition, a standard package I<Prima::PrintDialog> can be recommended
so the user can select a printer device and adjust its setup interactively.

=head1 API

=head2 Properties

=over

=item printer STRING

Selects a printer device, specified by its STRING identifier.
Can not select a device if a printing session is started.

=item resolution X, Y

A read-only property; returns a DPI horizontal and vertical resolution,
currently selected for a printer device. The user can change this,
if the printer device supports several resolutions, inside C<setup_dialog()>.

=item size WIDTH, HEIGHT

A read-only property; returns dimensions of a printer device page.
The user can change this, if the printer device supports several 
resolutions or page formats, inside C<setup_dialog()>.

=back

=head2 Methods

=over

=item abort_doc

Stops the printing session, returns the object to the disabled paiinting state.
Since the document can be passed to the system spooler, parts of it could have been sent
to a printing device when C<abort_doc()> is called, so some information
could still been printed.

=item begin_doc DOCUMENT_NAME = ""

Initiates the printing session, and triggers the object into the enabled painting
state. The document is assigned DOCUMENT_NAME string identifier.

=item begin_paint

Identical to C<begin_doc("")> call.

=item begin_paint_info

Triggers the object into the information painting state. In this state,
all graphic functions can be accessed, but no data is printed. Neither
C<new_page()> and C<abort_doc()> methods work. The information
mode is exited via C<end_paint_info()> method.

=item end_doc

Quits the printing session and delivers the document to a printer device.
Does not report eventual errors, occured during the spooling process -
the system is expected to take care about such situations.

=item end_paint

Identical to C<abort_doc()>.

=item end_paint_info

Quits the information painting mode, initiated by C<begin_paint_info()>
and returns the object into the disabled painting state.

=item font_encodings

Returns array of encodings, represented by strings, that are recognized by the system
and available in at least one font. Each system provides different
sets of encoding strings; the font encodings are not portable.

=item fonts NAME = '', ENCODING = ''

Returns hash of font hashes ( see L<Prima::Drawable>, Fonts section )
describing fonts of NAME font family and of ENCODING. If NAME is '' or C<undef>,
returns one fonts hash for each of the font families that match the ENCODING
string. If ENCODING is '' or C<undef>, no encoding match is performed.
If ENCODING is not valid ( not present in C<font_encodings> result), it is
treated as if it was '' or C<undef>.

In the special case, when both NAME and ENCODING are '' or C<undef>,
each font metric hash contains element C<encodings>, that points to
array of the font encodings, available for the fonts of NAME font family.

=item new_page

Finalizes the current page and starts a new blank page.

=item printers

Returns array of hashes, where each entry describes a printer device.
The hash consists of the following entries:

=over

=item name

A printer device name

=item device

A physical device name, that the printer is connected to

=item defaultPrinter

A boolean flag, 1 if the printer is default, 0 otherwise.

=back

=item setup_dialog

Invokes the system-provided printer device setup dialog.
In this setup, the user can adjust the capablities of the printer,
such as page setup, resolution, color, etc etc. 

=item get_default_printer

Returns a string, identifying a default printer device.

=item get_handle

Returns a system handle for a printer object.

=head1 AUTHOR

Dmitry Karasik, E<lt>dmitry@karasik.eu.orgE<gt>.

=head1 SEE ALSO

L<Prima>, L<Prima::Drawable>, L<Prima::PS::Printer>

