Glib::CodeGen(3pm) User Contributed Perl Documentation Glib::CodeGen(3pm)
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 v5.36.0 2022-11-04 Glib::CodeGen(3pm)