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

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       list), GHashTable, GArray, etc have all been replaced by	native Perl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 GA<paragraph>ran 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 v5.24.1			  2016-09-28			       Glib(3)

NAME | SYNOPSIS | ABSTRACT | DESCRIPTION | PERL VERSUS C | FILENAMES, URIS AND ENCODINGS | EXCEPTIONS | LOG MESSAGES | 64 BIT INTEGERS | EXPORTS | SEE ALSO | AUTHORS | COPYRIGHT AND LICENSE

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