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

NAME
       Glib::CodeGen - code generation utilities for Glib-based	bindings.

SYNOPSIS
	# usually in Makefile.PL
	use Glib::CodeGen;

	# most common, use all defaults
	Glib::CodeGen->parse_maps ('myprefix');
	Glib::CodeGen->write_boot;

	# more exotic, change everything
	Glib::CodeGen->parse_maps ('foo',
				   input => 'foo.maps',
				   header => 'foo-autogen.h',
				   typemap => 'foo.typemap',
				   register => 'register-foo.xsh');
	Glib::CodeGen->write_boot (filename => 'bootfoo.xsh',
				   glob	=> 'Foo*.xs',
				   ignore => '^(Foo|Foo::Bar)$');

	# add a	custom type handler (rarely necessary)
	Glib::CodeGen->add_type_handler	(FooType => \&gen_foo_stuff);
	# (see the section EXTENDING TYPE SUPPORT for more info.)

DESCRIPTION
       This module packages some of the	boilerplate code needed	for performing
       code generation typically used by perl bindings for gobject-based
       libraries, using	the Glib module	as a base.

       The default output filenames are	in the subdirectory 'build', which
       usually will be present if you are using	ExtUtils::Depends (as most
       Glib-based extensions probably should).

   METHODS
       Glib::CodeGen->write_boot;
       Glib::CodeGen->write_boot (KEY => VAL, ...)
	   Many	GObject-based libraries	to be bound to perl will be too	large
	   to put in a single XS file; however,	a single PM file typically
	   only	bootstraps one XS file's code.	"write_boot" generates an XSH
	   file	to be included from the	BOOT section of	that one bootstrapped
	   module, calling the boot code for all the other XS files in the
	   project.

	   Options are passed to the function in a set of key/val pairs, and
	   all options may default.

	     filename	  the name of the output file to be created.
			  the default is 'build/boot.xsh'.

	     glob	  a glob pattern that specifies	the names of
			  the xs files to scan for MODULE lines.
			  the default is 'xs/*.xs'.

	     xs_files	  use this to supply an	explicit list of file
			  names	(as an array reference)	to use instead
			  of a glob pattern.  the default is to	use
			  the glob pattern.

	     ignore	  regular expression matching any and all
			  module names which should be ignored,	i.e.
			  NOT included in the list of symbols to boot.
			  this parameter is extremely important	for
			  avoiding infinite loops at startup; see the
			  discussion for an explanation	and rationale.
			  the default is '^[^:]+$', or,	any name that
			  contains no colons, i.e., any	toplevel
			  package name.

	   This	function performs a glob (using	perl's builtin glob operator)
	   on the pattern specified by the 'glob' option to retrieve a list of
	   file	names.	It then	scans each file	in that	list for lines
	   matching the	pattern	"^MODULE" -- that is, the MODULE directive in
	   an XS file.	The module name	is pulled out and matched against the
	   regular expression specified	by the ignore parameter.  If this
	   module is not to be ignored,	we next	check to see if	the name has
	   been	seen.  If not, the name	will be	converted to a boot symbol
	   (basically, s/:/_/ and prepend "boot_") and this symbol will	be
	   added to a call to GPERL_CALL_BOOT in the generated file; it	is
	   then	marked as seen so we don't call	it again.

	   What	is this	all about, you ask?  In	order to bind an XSub to perl,
	   the C function must be registered with the interpreter.  This is
	   the function	of the "boot" code, which is typically called in the
	   bootstrapping process.  However, when multiple XS files are used
	   with	only one PM file, some other mechanism must call the boot code
	   from	each XS	file before any	of the function	therein	will be
	   available.

	   A typical setup for a multiple-XS, single-PM	module will be to call
	   the various bits of boot code from the BOOT:	section	of the
	   toplevel module's XS	file.

	   To use Gtk2 as an example, when you do 'use Gtk2', Gtk2.pm calls
	   bootstrap on	Gtk2, which calls the C	function boot_Gtk2.  This
	   function calls the boot symbols for all the other xs	files in the
	   module.  The	distinction is that the	toplevel module, Gtk2, has no
	   colons in its name.

	   "xsubpp" generates the boot function's name by replacing the	colons
	   in the MODULE name with underscores and prepending "boot_".	We
	   need	to be careful not to include the boot code for the
	   bootstrapped	module,	(say Toplevel, or Gtk2,	or whatever) because
	   the bootstrap code in Toplevel.pm will call boot_Toplevel when
	   loaded, and boot_Toplevel should actually include the file we are
	   creating here.

	   The default value for the ignore parameter ignores any name not
	   containing colons, because it is assumed that this will be a
	   toplevel module, and	any other packages/modules it boots will be
	   below this namespace, i.e., they will contain colons.  This
	   assumption holds true for Gtk2 and Gnome2, but obviously fails for
	   something like Gnome2::Canvas.  To boot that	module properly, you
	   must	use a regular expression such as "^Gnome2::Canvas$".

	   Note	that you can, of course, match more than just one name,	e.g.
	   "^(Foo|Foo::Bar)$", if you wanted to	have Foo::Bar be included in
	   the same dynamically	loaded object but only be booted when
	   absolutely necessary.  (If you get that to work, more power to
	   you.)

	   Also, since this code scans for ^MODULE, you	must comment the
	   MODULE section out with leading # marks if you want to hide it from
	   "write_boot".

       Glib::CodeGen->parse_maps (PREFIX, [KEY => VAL, ...])
	   Convention within Glib/Gtk2 and friends is to use preprocessor
	   macros in the style of SvMyType and newSVMyType to get values in
	   and out of perl, and	to use those same macros from both hand-
	   written code	as well	as the typemaps.  However, if you have a lot
	   of types in your library (such as the nearly	200 types in Gtk+
	   2.x), then writing those macros becomes incredibly tedious,
	   especially so when you factor in all	of the variants	and such.

	   So, this function can turn a	flat file containing terse
	   descriptions	of the types into a header containing all the cast
	   macros, a typemap file using	them, and an XSH file containing the
	   proper code to register each	of those types (to be included by your
	   module's BOOT code).

	   The PREFIX is mandatory, and	is used	in some	of the resulting
	   filenames, You can also override the	defaults by providing key=>val
	   pairs:

	     input    input file name.	default	is 'maps'.  if this
		      key's value is an	array reference, all the
		      filenames	in the array will be scanned.
	     header   name of the header file to create, default is
		      build/$prefix-autogen.h
	     typemap  name of the typemap file to create, default is
		      build/$prefix.typemap
	     register name of the xsh file to contain all of the
		      type registrations, default is build/register.xsh

	   the maps file is a table of type descriptions, one per line,	with
	   fields separated by whitespace.  the	fields should be:

	     TYPE macro	   e.g., GTK_TYPE_WIDGET
	     class name	   e.g.	GtkWidget, name	of the C type
	     base type	   one of GObject, GBoxed, GEnum, GFlags.
			   To support other base types,	see
			   EXTENDING TYPE SUPPORT for info on
			   on how to add a custom type handler.
	     package	   name	of the perl package to which this
			   class name should be	mapped,	e.g.
			   Gtk2::Widget

	   As a	special	case, you can also use this same format	to register
	   error domains; in this case two of the four columns take on
	   slightly different meanings:

	     domain macro     e.g., GDK_PIXBUF_ERROR
	     enum type macro  e.g., GDK_TYPE_PIXBUF_ERROR
	     base type	      GError
	     package	      name of the Perl package to which	this
			      class name should	be mapped, e.g.,
			      Gtk2::Gdk::Pixbuf::Error.

EXTENDING TYPE SUPPORT
       "parse_maps" uses the base type entry in	each maps record to decide how
       to generate output for that type.  In the base module, type support is
       included	for the	base types provided by Glib.  It is easy to add
       support for your	own types, by merely adding a type handler.  This type
       handler will call utility functions to add typemaps, BOOT lines,	and
       header lines.

       Glib::CodeGen->add_type_handler ($base_type => $handler)
	   $base_type (string) C name of the base type to handle.
	   $handler (subroutine) Callback used to handle this type.

	   Use $handler	to generate output for records whose base type is
	   $base_type.	$base_type is the C type name as found in the third
	   column of a maps file entry.

	   $handler will be called with	the (possibly preprocessed) contents
	   of the current maps file record, and	should call the	"add_typemap",
	   "add_register", and "add_header" functions to set up	the necessary
	   C/XS	glue for that type.

	   For example:

	     Glib::CodeGen->add_type_handler (CoolThing	=> sub {
		 my ($typemacro, $classname, $base, $package) =	@_;

		 # $typemacro is the C type macro, like	COOL_TYPE_THING.
		 # $classname is the actual C type name, like CoolFooThing.
		 # $base is the	C name of the base type.  If CoolFooThing
		 #     isa CoolThing, $base will be CoolThing.	This
		 #     parameter is useful when	using the same type handler
		 #     for multiple base types.
		 # $package is the package name	that corresponds to
		 #     $classname, as specified	in the maps file.

		 ...
	     });

       add_typemap $type, $typemap [, $input, $output]
	   Add a typemap entry for $type, named	$typemap.  If $input and/or
	   $output are defined,	their text will	be used	as the "INPUT" and/or
	   "OUTPUT" typemap implementations (respectively) for $typemap.  Note
	   that	in general, you'll use "T_GPERL_GENERIC_WRAPPER" or some other
	   existing typemap for	$typemap, so $input and	$output	are very
	   rarely used.

	   Example:

	     # map $classname pointers and all their variants to the generic
	     # wrapper typemap.
	     add_typemap "$classname *", "T_GPERL_GENERIC_WRAPPER";
	     add_typemap "const	$classname *", "T_GPERL_GENERIC_WRAPPER";
	     add_typemap "$classname\_ornull *", "T_GPERL_GENERIC_WRAPPER";
	     add_typemap "const	$classname\_ornull *", "T_GPERL_GENERIC_WRAPPER";
	     add_typemap "$classname\_own *", "T_GPERL_GENERIC_WRAPPER";
	     add_typemap "$classname\_copy *", "T_GPERL_GENERIC_WRAPPER";
	     add_typemap "$classname\_own_ornull *", "T_GPERL_GENERIC_WRAPPER";

	     # custom code for an int-like enum:
	     add_typemap $class	=> T_FOO,
			 "\$var	= foo_unwrap (\$arg);",	# input
			 "\$arg	= foo_wrap (\$var);"; #	output

       add_register $text
	   Add $text to	the generated "register.xsh".  This is usually used
	   for registering types with the bindings, e.g.:

	      add_register "#ifdef $typemacro\n"
		     . "gperl_register_object ($typemacro, \"$package\");\n"
		     . "#endif /* $typemacro */";

       add_header $text
	   Add $text to	the generated C	header.	 You'll	put variant typedefs
	   and wrap/unwrap macros in the header, and will usually want to wrap
	   the declarations in "#ifdef $typemacro" for safety.

BUGS
       GInterfaces are mostly just ignored.

       The code	is ugly.

AUTHOR
       muppet <scott at	asofyet	dot org>

COPYRIGHT
       Copyright (C) 2003-2005,	2013 by	the gtk2-perl team (see	the file
       AUTHORS for the full list)

       This library is free software; you can redistribute it and/or modify it
       under the terms of the GNU Library General Public License as published
       by the Free Software Foundation;	either version 2.1 of the License, or
       (at your	option)	any later version.

       This library is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A	PARTICULAR PURPOSE.  See the GNU
       Library General Public License for more details.

       You should have received	a copy of the GNU Library General Public
       License along with this library;	if not,	write to the Free Software
       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
       02110-1301 USA.

perl v5.32.0			  2020-06-06		      Glib::CodeGen(3)

NAME | SYNOPSIS | DESCRIPTION | EXTENDING TYPE SUPPORT | BUGS | AUTHOR | COPYRIGHT

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