=head1 NAME

Glib::version -  Library Versioning Utilities

=cut

=for position SYNOPSIS

=head1 SYNOPSIS

  # require at least version 1.021 of the Glib module
  use Glib '1.021';

  # g_set_application_name() was introduced in GLib 2.2.0, and
  # first supported by version 1.040 of the Glib Perl module.
  if ($Glib::VERSION >= 1.040 and Glib->CHECK_VERSION (2,2,0)) {
     Glib::set_application_name ('My Cool Program');
  }

=for position DESCRIPTION

=head1 DESCRIPTION

Both the Glib module and the GLib C library are works-in-progress, and 
their interfaces grow over time.  As more features are added to each, 
and your code uses those new features, you will introduce 
version-specific dependencies, and naturally, you'll want to be able to 
code around them.  Enter the versioning API.

For simple Perl modules, a single version number is sufficient; 
however, Glib is a binding to another software library, and this 
introduces some complexity.  We have three versions that fully specify 
the API available to you.

=over

=item Perl Bindings Version

Perl modules use a version number, and Glib is no exception.  
I<$Glib::VERSION> is the version of the current Glib module.  By ad hoc 
convention, gtk2-perl modules generally use version numbers in the form 
x.yyz, where even yy values denote stable releases and z is a 
patchlevel.

   $Glib::VERSION
   use Glib 1.040; # require at least version 1.040

=item Compile-time ("Bound") Library Version

This is the version of the GLib C library that was available when the 
Perl module was compiled and installed.  These version constants are 
equivalent to the version macros provided in the GLib C headers.  GLib 
uses a major.minor.micro convention, where even minor versions are 
stable.  (gtk2-perl does not officially support unstable versions.)

   Glib::MAJOR_VERSION
   Glib::MINOR_VERSION
   Glib::MICRO_VERSION
   Glib->CHECK_VERSION($maj,$min,$mic)

=item Run-time ("Linked") Library Version

This is the version of the GLib C library that is available at run 
time; it may be newer than the compile-time version, but should never 
be older.  These are equivalent to the version variables exported by 
the GLib C library.

   Glib::major_version
   Glib::minor_version
   Glib::micro_version

=back

=head2 Which one do I use when?

Where do you use which version?  It depends entirely on what you're 
doing.  Let's explain by example:

=over

=item o Use the Perl module version for bindings support issues

You need to register a new enum for use as the type of an object 
property.  This is something you can do with all versions of the 
underlying C library, but which wasn't supported in the Glib Perl 
module until $Glib::VERSION >= 1.040.

=item o Use the bound version for library features

You want to call Glib::set_application_name to set a human-readable name
for your application (which is used by various parts of Gtk2 and Gnome2).
g_set_application_name() (the underlying C function) was added in version
2.2.0 of glib, and support for it was introduced into the Glib Perl module
in Glib version 1.040.  However, you can build the Perl module against any
stable 2.x.x version of glib, so you might not have that function available
even if your Glib module is new enough!
  Thus, you need to check two things to see if the this function is 
available:

   if ($Glib::VERSION >= 1.040 && Glib->CHECK_VERSION (2,2,0)) {
       # it's available, and we can call it!
       Glib::set_application_name ('My Cool Application');
   }

Now what happens if you installed the Perl module when your system had 
glib 2.0.6, and you upgraded glib to 2.4.1?  Wouldn't g_set_application_name() 
be available?  Well, it's there, under the hood, but the bindings were 
compiled when it wasn't there, so you won't be able to call it! 
That's why we check the "bound" or compile-time version.  By the way, to 
enable support for the new function, you'd need to reinstall (or upgrade)
the Perl module.

=item o Use the linked version for runtime work-arounds

Suppose there's a function whose API did not change, but whose 
implementation had a bug in one version that was fixed in another 
version.  To determine whether you need to apply a workaround, you 
would check the version that is actually being used at runtime.

   if (Glib::major_version == 2 &&
       Glib::minor_version == 2 &&
       Glib::micro_version == 1) {
      # work around bug that exists only in glib 2.2.1.
   }

In practice, such situations are very rare.

=back

=cut



=for object Glib::version Library Versioning Utilities
=cut




=head1 METHODS

=head2 boolean = Glib-E<gt>B<CHECK_VERSION> ($required_major, $required_minor, $required_micro)

=over

=item * $required_major (integer) 

=item * $required_minor (integer) 

=item * $required_micro (integer) 

=back

Provides a mechanism for checking the version information that Glib was
compiled against. Essentially equvilent to the macro GLIB_CHECK_VERSION.

=head2 (MAJOR, MINOR, MICRO) = Glib->B<GET_VERSION_INFO>

Shorthand to fetch as a list the glib version for which Glib was compiled.
See C<Glib::MAJOR_VERSION>, etc.

=head2 integer = Glib::MAJOR_VERSION 

Provides access to the version information that Glib was compiled against.
Essentially equivalent to the #define's GLIB_MAJOR_VERSION.

=head2 integer = Glib::MICRO_VERSION 

Provides access to the version information that Glib was compiled against.
Essentially equivalent to the #define's GLIB_MICRO_VERSION.

=head2 integer = Glib::MINOR_VERSION 

Provides access to the version information that Glib was compiled against.
Essentially equivalent to the #define's GLIB_MINOR_VERSION.

=head2 integer = Glib::major_version 

Provides access to the version information that Glib is linked against.
Essentially equivalent to the global variable glib_major_version.

=head2 integer = Glib::micro_version 

Provides access to the version information that Glib is linked against.
Essentially equivalent to the global variable glib_micro_version.

=head2 integer = Glib::minor_version 

Provides access to the version information that Glib is linked against.
Essentially equivalent to the global variable glib_minor_version.



=cut


=head1 SEE ALSO

L<Glib>


=cut


=head1 COPYRIGHT

Copyright (C) 2003-2011 by the gtk2-perl team.

This software is licensed under the LGPL.  See L<Glib> for a full notice.



=cut

