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Glib(3pm)	      User Contributed Perl Documentation	     Glib(3pm)

NAME
       Glib - Perl wrappers for the GLib utility and Object libraries

SYNOPSIS
	 use Glib;

ABSTRACT
       This module provides perl access to GLib and GLib's GObject libraries.
       GLib is a portability and utility library; GObject provides a generic
       type system with inheritance and a powerful signal system.  Together
       these libraries are used as the foundation for many of the libraries
       that make up the Gnome environment, and are used in many unrelated
       projects.

DESCRIPTION
       This wrapper attempts to provide a perlish interface while remaining as
       true as possible to the underlying C API, so that any reference
       materials you can find on using GLib may still apply to using the
       libraries from perl.  This module also provides facilities for creating
       wrappers for other GObject-based libraries.  The "SEE ALSO" section
       contains pointers to all sorts of good information.

PERL VERSUS C
       GLib provides to C programs many of the same facilities Perl offers
       natively.  Where GLib's functionality overlaps Perl's, Perl's is
       favored.	 Some concepts have been eliminated entirely, as Perl is a
       higher-level language than C.  In other instances we've had to add or
       change APIs to make sense in Perl.  Here's a quick run-down:

   Perl Already Does That
       The GLib types GList (a doubly-linked list), GSList (singly-linked
       list), GHashTable, GArray, etc have all been replaced by native Perl
       datatypes.  In fact, many functions which take GLists or arrays simply
       accept lists on the Perl stack.	For the most part, GIOChannels are no
       more functional than Perl file handles, so you won't see any
       GIOChannels.  GClosures are not visible at the Perl level, because Perl
       code references do the same thing.  Just about any function taking
       either a C function pointer or a GClosure will accept a code reference
       in Perl.	 (In fact, you can probably get away with just a subroutine
       name in many spots, provided you aren't using strict subs.)

   Don't Worry About That
       Some concepts have been eliminated; you need never worry about
       reference-counting on GObjects or having to free GBoxed structures.
       Perl is a garbage-collected language, and we've put a lot of work into
       making the bindings take care of memory for you in a way that feels
       natural to a Perl developer.  You won't see GValues in Perl (that's
       just a C structure with Perl scalar envy, anyway).

   This Is Now That
       Other GLib concepts have been converted to an analogous Perl concept.

       The GType id will never be seen in Perl, as the package name serves
       that purpose.  Several packages corresponding to the GTypes of the
       fundamental types have been registered for you:

	G_TYPE_STRING	  Glib::String
	G_TYPE_INT	  Glib::Int
	G_TYPE_UINT	  Glib::UInt
	G_TYPE_DOUBLE	  Glib::Double
	G_TYPE_BOOLEAN	  Glib::Boolean

       The remaining fundamentals (char/uchar, short, float, etc) are also
       registered so that we can properly interact with properties of C
       objects, but perl really only uses ints, uints, and doubles.  Oh, and
       we created a GBoxed type for Perl scalars so you can use scalars where
       any boxed type would be allowed (e.g.  GtkTreeModel columns):

	Glib::Scalar

       Functions that can return false and set a GError in C raise an
       exception in Perl, using an exception object based on the GError for
       $@; see Glib::Error.  Trapping exceptions in signals is a sticky issue,
       so they get their own section; see EXCEPTIONS.

       Enumerations and flags are treated as strings and arrays of strings,
       respectively.  GLib provides a way to register nicknames for
       enumeration values, and the Perl bindings use these nicknames for the
       real values, so that we never have to deal with numbers in Perl. This
       can get a little cumbersome for bitfields, but it's very nice when you
       forget a flag value, as the bindings will tell you what values are
       accepted when you pass something invalid. Also, the bindings consider
       the - and _ characters to be equivalent, so that signal and property
       names can be properly stringified by the => operator.  For example, the
       following are equivalent:

	 # property foo-matic of type FooType, using the
	 # value FOO_SOMETHING_COOL.  its nickname would be
	 # 'something-cool'.  you may use either the full
	 # name or the nickname when supplying values to perl.
	 $object->set ('foo-matic', 'FOO_SOMETHING_COOL');
	 $object->set ('foo_matic', 'something_cool');
	 $object->set (foo_matic => 'something-cool');

       Beware that Perl will always return to you the nickname form, with the
       dash.

       Flags have some additional magic abilities in the form of overloaded
       operators:

	 + or |	  union of two flagsets ("add")
	 -	  difference of two flagsets ("sub", "remove")
	 * or &	  intersection of two bitsets ("and")
	 / or ^	  symmetric difference ("xor", you will rarely need this)
	 >=	  contains-operator ("is the left set a superset of the right set?")
	 ==	  equality

       In addition, flags in boolean context indicate whether they are empty
       or not, which allows you to write common operations naturally:

	 $widget->set_events ($widget->get_events - "motion_notify_mask");
	 $widget->set_events ($widget->get_events - ["motion_notify_mask",
						     "button_press_mask"]);

	 # shift pressed (both work, it's a matter of taste)
	 if ($event->state >= "shift-mask") { ...
	 if ($event->state * "shift-mask") { ...

	 # either shift OR control pressed?
	 if ($event->state * ["shift-mask", "control-mask"]) { ...

	 # both shift AND control pressed?
	 if ($event->state >= ["shift-mask", "control-mask"]) { ...

       In general, "+" and "-" work as expected to add or remove flags. To
       test whether any bits are set in a mask, you use "$mask * ...", and to
       test whether all bits are set in a mask, you use "$mask >= ...".

       When dereferenced as an array @$flags or "$flags->[...]", you can
       access the flag values directly as strings (but you are not allowed to
       modify the array), and when stringified "$flags" a flags value will
       output a human-readable version of its contents.

   It's All the Same
       For the most part, the remaining bits of GLib are unchanged.  GMainLoop
       is now Glib::MainLoop, GObject is now Glib::Object, GBoxed is now
       Glib::Boxed, etc.

FILENAMES, URIS AND ENCODINGS
       Perl knows two datatypes, unicode text and binary bytes. Filenames on a
       system that doesn't use a utf-8 locale are often stored in a local
       encoding ("binary bytes"). Gtk+ and descendants, however, internally
       work in unicode most of the time, so when feeding a filename into a
       GLib/Gtk+ function that expects a filename, you first need to convert
       it from the local encoding to unicode.

       This involves some elaborate guessing, which perl currently avoids, but
       GLib and Gtk+ do. As an exception, some Gtk+ functions want a filename
       in local encoding, but the perl interface usually works around this by
       automatically converting it for you.

       In short: Everything should be in unicode on the perl level.

       The following functions expose the conversion algorithm that GLib uses.

       These functions are only necessary when you want to use perl functions
       to manage filenames returned by a GLib/Gtk+ function, or when you feed
       filenames into GLib/Gtk+ functions that have their source outside your
       program (e.g. commandline arguments, readdir results etc.).

       These functions are available as exports by request (see "Exports"),
       and also support method invocation syntax for pathological consistency
       with the OO syntax of the rest of the bindings.

       $filename = filename_to_unicode $filename_in_local_encoding
       $filename = Glib->filename_to_unicode ($filename_in_local_encoding)
	   Convert a perl string that supposedly contains a filename in local
	   encoding into a filename represented as unicode, the same way that
	   GLib does it internally.

	   Example:

	      $gtkfilesel->set_filename (filename_to_unicode $ARGV[1]);

	   This function will croak() if the conversion cannot be made, e.g.,
	   because the utf-8 is invalid.

       $filename_in_local_encoding = filename_from_unicode $filename
       $filename_in_local_encoding = Glib->filename_from_unicode ($filename)
	   Converts a perl string containing a filename into a filename in the
	   local encoding in the same way GLib does it.

	   Example:

	      open MY, "<", filename_from_unicode $gtkfilesel->get_filename;

       It might be useful to know that perl currently has no policy at all
       regarding filename issues, if your scalar happens to be in utf-8
       internally it will use utf-8, if it happens to be stored as bytes, it
       will use it as-is.

       When dealing with filenames that you need to display, there is a much
       easier way, as of Glib 1.120 and glib 2.6.0:

       $uft8_string = filename_display_name ($filename)
       $uft8_string = filename_display_basename ($filename)
	   Given a $filename in filename encoding, return the filename, or
	   just the file's basename, in utf-8.	Unlike the other functions
	   described above, this one is guaranteed to return valid utf-8, but
	   the conversion is not necessarily reversible.  These functions are
	   intended to be used for failsafe display of filenames, for example
	   in gtk+ labels.

	   Since glib 2.6, Glib 1.12

       The following convert filenames to and from URI encoding.  (See also
       URI::file.)

       $string = filename_to_uri ($filename, $hostname)
       $string = Glib->filename_to_uri ($filename, $hostname)
	   Return a "file://" schema URI for a filename.  Unsafe and non-ascii
	   chars in $filename are escaped with URI "%" forms.

	   $filename must be an absolute path as a byte string in local
	   filesystem encoding.	 $hostname is a utf-8 string, or empty or
	   "undef" for no host specified.  For example,

	       filename_to_uri ('/my/x%y/<dir>/foo.html', undef);
	       # returns 'file:///my/x%25y/%3Cdir%3E/foo.html'

	   If $filename is a relative path or $hostname doesn't look like a
	   hostname then "filename_to_uri" croaks with a "Glib::Error".

	   When using the class style "Glib->filename_to_uri" remember that
	   the $hostname argument is mandatory.	 If you forget then it looks
	   like a 2-argument call with filename of "Glib" and hostname of what
	   you meant to be the filename.

       $filename = filename_from_uri ($uri)
       ($filename, $hostname) = filename_from_uri ($uri)
	   Extract the filename and hostname from a "file://" schema URI.  In
	   scalar context just the filename is returned, in array context both
	   filename and hostname are returned.

	   The filename returned is bytes in the local filesystem encoding and
	   with the OS path separator character.  The hostname returned is
	   utf-8.  For example,

	       ($f,$h) = filename_from_uri ('file://foo.com/r%26b/bar.html');
	       # returns '/r&b/bar.html' and 'foo.com' on Unix

	   If $uri is not a "file:", or is mal-formed, or the hostname part
	   doesn't look like a host name then "filename_from_uri" croaks with
	   a "Glib::Error".

EXCEPTIONS
       The C language doesn't support exceptions; GLib is a C library, and of
       course doesn't support exceptions either.  In Perl, we use die and eval
       to raise and trap exceptions as a rather common practice.  So, the
       bindings have to work a little black magic behind the scenes to keep
       GLib from exploding when the Perl program uses exceptions.
       Unfortunately, a little of this magic has to leak out to where you can
       see it at the Perl level.

       Signal and event handlers are run in an eval context; if an exception
       occurs in such a handler and you don't catch it, Perl will report that
       an error occurred, and then go on about its business like nothing
       happened.

       You may register subroutines as exception handlers, to be called when
       such an exception is trapped.  Another function removes them for you.

	 $tag = Glib->install_exception_handler (\&my_handler);
	 Glib->remove_exception_handler ($tag);

       The exception handler will get a fresh copy of the $@ of the offending
       exception on the argument stack, and is expected to return non-zero if
       the handler is to remain installed.  If it returns false, the handler
       will be removed.

	 sub my_handler {
	     if ($_[0] =~ m/ftang quisinart/) {
		  clean_up_after_ftang ();
	     }
	     1; # live to fight another day
	 }

       You can register as many handlers as you like; they will all run
       independently.

       An important thing to remember is that exceptions do not cross main
       loops.  In fact, exceptions are completely distinct from main loops.
       If you need to quit a main loop when an exception occurs, install a
       handler that quits the main loop, but also ask yourself if you are
       using exceptions for flow control or exception handling.

LOG MESSAGES
       GLib's g_log function provides a flexible mechanism for reporting
       messages, and most GLib-based C libraries use this mechanism for
       warnings, assertions, critical messages, etc.  The Perl bindings offer
       a mechanism for routing these messages through Perl's native system,
       warn() and die().  Extensions should register the log domains they wrap
       for this to happen fluidly.  [FIXME say more here]

64 BIT INTEGERS
       Since perl's integer data type can only hold 32 bit values on all 32
       bit machines and even on some 64 bit machines, Glib converts 64 bit
       integers to and from strings if necessary.  These strings can then be
       used to feed one of the various big integer modules.  Make sure you
       don't let your strings get into numerical context before passing them
       into a Glib function because in this case, perl will convert the number
       to scientific notation which at this point is not understood by Glib's
       converters.

       Here is an overview of what big integer modules are available.  First
       of all, there's Math::BigInt.  It has everything you will ever need,
       but its pure-Perl implementation is also rather slow.  There are
       multiple ways around this, though.

       Math::BigInt::FastCalc
	   Math::BigInt::FastCalc can help avoid the glacial speed of vanilla
	   Math::BigInt::Calc.	Recent versions of Math::BigInt will
	   automatically use Math::BigInt::FastCalc in place of
	   Math::BigInt::Calc when available.  Other options include
	   Math::BigInt::GMP or Math::BigInt::Pari, which however have much
	   larger dependencies.

       Math::BigInt::Lite
	   Then there's Math::BigInt::Lite, which uses native Perl integer
	   operations as long as Perl integers have sufficient range, and
	   upgrades itself to Math::BigInt when Perl integers would overflow.
	   This must be used in place of Math::BigInt.

       bigint / bignum / bigfloat
	   Finally, there's the bigint/bignum/bigfloat pragmata, which
	   automatically load the corresponding Math:: modules and which will
	   autobox constants.  bignum/bigint will automatically use
	   Math::BigInt::Lite if it's available.

EXPORTS
       For the most part, gtk2-perl avoids exporting things.  Nothing is
       exported by default, but some functions and constants in Glib are
       available by request; you can also get all of them with the export tag
       "all".

       Tag: constants
	     TRUE
	     FALSE
	     SOURCE_CONTINUE
	     SOURCE_REMOVE
	     G_PRIORITY_HIGH
	     G_PRIORITY_DEFAULT
	     G_PRIORITY_HIGH_IDLE
	     G_PRIORITY_DEFAULT_IDLE
	     G_PRIORITY_LOW
	     G_PARAM_READWRITE

       Tag: functions
	     filename_from_unicode
	     filename_to_unicode
	     filename_from_uri
	     filename_to_uri
	     filename_display_basename
	     filename_display_name

SEE ALSO
       Glib::Object::Subclass explains how to create your own gobject
       subclasses in Perl.

       Glib::index lists the automatically-generated API reference for the
       various packages in Glib.

       This module is the basis for the Gtk2 module, so most of the references
       you'll be able to find about this one are tied to that one.  The perl
       interface aims to be very simply related to the C API, so see the C API
       reference documentation:

	 GLib - http://developer.gnome.org/doc/API/2.0/glib/
	 GObject - http://developer.gnome.org/doc/API/2.0/gobject/

       This module serves as the foundation for any module which needs to bind
       GLib-based C libraries to perl.

	 Glib::devel - Binding developer's overview of Glib's internals
	 Glib::xsapi - internal API reference for GPerl
	 Glib::ParseXSDoc - extract API docs from xs sources.
	 Glib::GenPod - turn the output of Glib::ParseXSDoc into POD
	 Glib::MakeHelper - Makefile.PL utilities for Glib-based extensions

	 Yet another document, available separately, ties it all together:
	   http://gtk2-perl.sourceforge.net/doc/binding_howto.pod.html

       For gtk2-perl itself, see its website at

	 gtk2-perl - http://gtk2-perl.sourceforge.net/

       A mailing list exists for discussion of using gtk2-perl and related
       modules.	 Archives and subscription information are available at
       http://lists.gnome.org/.

AUTHORS
       muppet, <scott at asofyet dot org>, who borrowed heavily from the work
       of Goeran Thyni, <gthyni at kirra dot net> and Guillaume Cottenceau <gc
       at mandrakesoft dot com> on the first gtk2-perl module, and from the
       sourcecode of the original gtk-perl and pygtk projects.	Marc Lehmann
       <pcg at goof dot com> did lots of great work on the magic of making
       Glib::Object wrapper and subclassing work like they should.  Ross
       McFarland <rwmcfa1 at neces dot com> wrote quite a bit of the
       documentation generation tools.	Torsten Schoenfeld <kaffeetisch at web
       dot de> contributed little patches and tests here and there.

COPYRIGHT AND LICENSE
       Copyright 2003-2011 by muppet and the gtk2-perl team

       This library is free software; you can redistribute it and/or modify it
       under the terms of the Lesser General Public License (LGPL).  For more
       information, see http://www.fsf.org/licenses/lgpl.txt

perl v5.18.1			  2013-12-31			     Glib(3pm)
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