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       GOB2 - The GObject Builder


       gob2 [ option ] ...  file


       GObject  Builder  is  a simple preprocessor for easily creating GObject
       objects.  It does not parse any C code and ignores any C errors.  It is
       in  spirit  similar  to  things like lex or yacc.  In some ways it also
       resembles java.  But it  is  really  just  a  simple  preprocessor  for
       creating  GObjects  for  use  in  C  or C++ and it is not a programming


       -? -h --help
              Display a simple help screen.

              Display version information

       -w --exit-on-warn
              Exit with an error code even when you encounter a warning.

              Exit with an error only on errors, not on warnings, this is  the

              Generate C++ code.

              Never add the extern "C" to the header.

              Never  generate any code with GNU C extensions.  However all the
              GNU C extensions are always wrapped in #ifdef __GNUC__, so  code
              using  them  compiles correctly even on non-GNU compilers.  This
              option is for purists only.  (using GNU extensions some warnings
              are  eliminated,  some  ugly  hacks and there is better argument
              type safety, so it´s good to use them)

              Don´t touch output files unless  they  really  changed  (implies
              --no-touch-headers).   Be  careful  with  automake,  see section

              Don´t touch the generated header file unless it really  changed,
              this avoids spurious rebuilds, but can confuse some make systems
              (automake in particular), so  it  is  not  enabled  by  default.
              Private header is still touched even if unchanged however.

              Always  create  a <basename>-private.h file, even if it would be

              Create the private header only if it would have something in it,
              that  is,  if  there  are some private data members or protected
              methods.  This is the default.

              Never create a private header file.  If we use any private  data
              members,  define  the private data structure at the point in the
              .c source where the class definition begins.

       --m4   Preprocess source with m4. Following args will be passed to  m4.

              Print directory that will be searched for m4 files.

       -n --no-write
              Do  not  write  any output files, just check syntax of the input

              Do not print out the ´#line´ statements into the output.  Useful
              for debugging the auto-generated generated code.

              Do  not create the Self and SelfClass type aliases and the SELF,
              IS_SELF and SELF_CLASS macros.

              Do not remove the initial underscore from method names.

              Always include the private pointer in the  public  header  file.
              This  is  useful  for  files which are part of a library and you
              want to reserve the right  to  add  some  private  data  members
              without breaking binary compatibility.

       -o --output-dir
              The directory into which output should be placed.

              Replace  default  `-´  file  name  separator.   If  no separator
              character is given then none is used.  Only one character can be


       Because we need to parse out different parts of the typename, sometimes
       you need to specify the typename with some special syntax.   Types  are
       specified  in  capitalized  form  and  words are separated by `:´.  The
       first word of the type (which can be empty) is the  "namespace".   This
       fact  is  for  example  used  for  the type checking macro and the type
       macro.  For "Gtk:New:Button", the macros will be GTK_IS_NEW_BUTTON  and
       GTK_TYPE_NEW_BUTTON.   This colon separated format of typenames is used
       in the class declaration header and for method argument types.


       The filenames are created from the typename.  The words  are  separated
       by  `-´  (this  can be changed with --file-sep option) and all in lower
       case.  For example for an object named "Gtk:New:Button", the files  are
       gtk-new-button.c  and gtk-new-button.h.  If you are using C++ mode, the
       output .c file will in fact be a .cc file.  If  you  have  any  private
       data  members,  a  private  header  file  will  also be created, called
       <basename>-private.h   (for   the   example   above   it    would    be
       gtk-new-button-private.h).   The  public  header  file is created to be
       human readable and to be used as a reference to  the  object.   The  .c
       source  file  is not created as a human readable source and is littered
       with #line statements, which make the compiler attempt to point you  to
       the right line in your .gob file in case of parsing errors.  The output
       should not be edited by hand, and you should only edit the .gob file.


       To include some code directly in the output C file begin with  ´%{´  on
       an  empty  line  and  end the code with a ´%}´ on an empty line.  These
       sections will appear in the output files in the order they  are  given.
       There  are  several  other sections to which you can put code.  You can
       put it in the ´header´ section (which can be abbreviated  ´h´)  and  it
       will  go  into  the  public  header  file.   You can also put it in the
       ´privateheader´ section (abbreviated ´ph´) which will make the code  go
       into  the  private  header  file.   Sometimes you want some code (other
       includes) to appear before the extern "C" and  the  protecting  define.
       To  do  this  you  can put them into the ´headertop´ (or ´ht´) section.
       You may wish to include code or comments in all the  files,  which  you
       can  do  by  putting  them into the ´all´ (or ´a´) section.  Similarly,
       code you wish to appear at the top of all files go in the ´alltop´  (or
       ´at´)   section.   Finally,  ´afterdecls´  includes  code  between  the
       declarations and the method implementations, but note that ´afterdecls´
       requires version 2.0.16.  For example:

               /* this will be on top of all output files */

               /* this will be on top of the public header */

               /* this will go into the private header file */

               /* will be included in the header */
               void somefunc(int i);

               /* will be included in all files */

               /* between the declarations and the method implementations */
               /* Requires gob version 2.0.16 */

               /* will be included in the C file */
               void somefunc(int i)
                     /* some code */


       Gob  will automatically include the class header file at the top of the
       .c source file.  If you wish to include  it  somewhere  else,  put  the
       include  into  some  %{  %} section above the class definition, and gob
       will not include it automatically.  This way  you  can  avoid  circular
       includes  and  control  where  in  the  file do you want to include the

       If you made any data members private, gob will  also  create  a  source
       file  that  will  be  called  <basename>-private.h.  Same rule as above
       applies for this just as it does for the regular header file.   If  you
       do  explicitly  include  the  regular  header  file,  you should always
       include this private header file below it.  That is,  if  you  use  any
       private   data   members.   If  you  don´t,  the  private  header  file
       automatically includes the public header  file,  and  thus  the  public
       header file will be indirectly included at the very top of the file.


       There  can  be only one class per input file.  Defining a class is sort
       of like in Java, you define the class and write  inline  code  directly
       into  the  class definition.  To define a class you need to specify the
       new object name and the name of the object from  which  it  is  derived
       from,  such as this "class <new type> from <parent type> { <class code>
       }".  For example:

         class Gtk:New:Button from Gtk:Button {
              <class code>

       To  make  an  abstract  class  (to   pass   G_TYPE_FLAG_ABSTRACT)   add
       ´(abstract)´  before  the curly braces above.  This works since version


       There are five types of data members.  Three of them  are  normal  data
       members,  one is class wide (global) in scope and one is a virtual one,
       usually linked to a normal data member or a  class  wide  data  member.
       The  three  normal  data  members  are  public,  protected and private.
       Public  and  protected  are  basically  just  entries  in  the   object
       structure,  while  private  has  it´s own dynamically allocated private
       structure.  Protected members are always put after the  public  one  in
       the  structure  and  are marked protected in the header file.  There is
       only one identifier allowed per typename unlike in normal C.  Example:

         public int i;
         private GtkWidget *h;
         protected long k;

       Public and protected data members are accessed normally as  members  of
       the object struct.  Example where ´i´ is as above a public data member:

         object->i = 1;

       The private data members are defined  in  a  structure  which  is  only
       available  inside  the  .c file, or by including a private header file.
       You must access them using the structure _priv.  Example where  ´h´  is
       the private data member (as in the above example):

         object->_priv->h = NULL;

       The  _priv structure is defined in the <basename>-private.h.  This file
       is automatically included if you don´t include it yourself.  You should
       always  explicitly  include it in your .gob file if you explicitly also
       include the main header file.  The reason it is a separate header  file
       is  that  you  can  also include it in other places that need to access
       this objects private  data,  such  as  if  you  have  the  majority  of
       functionality  of  an  object  in  a separate .c file.  Or if a derived
       object needs to access the protected methods.

       In case you use the --no-private-header option, no private header  file
       is  created  and  you can only access the _priv pointer below the class
       definition in the .gob file.

       Also note that this structure is dynamically allocated, and is freed in
       the finalize handler.  If you override the finalized handler, your code
       will be run first and only then will the _priv structure be freed.

       Classwide data members:

       Sometimes you want a datamember to be shared by all objects.  You  then
       need  the "classwide" scope keyword.  So for example the following adds
       a global member foo:

         classwide int foo;

       To  access  the  member  you  can  use  the  SELF_GET_CLASS  macro  (or
       YOUR_OBJECT_NAME_GET_CLASS)  to  get  at the class.  Thus the following
       would work:

         SELF_GET_CLASS(object)->foo = 20;

       Automatic Initialization:

       You can automatically initialize the public private and protected  data
       members  without  having  to add an init method.  The advantage here is
       that initialization is kept close to the definition of the data  member
       and  thus it´s easier to check.  To do this, just add a ´=´ followed by
       a number or a token.  It is also possible to include arbitrary  C  code
       for  more  elaborate initializations by putting it all in curly braces.
       Note that the curly braces will not be printed  into  the  output,  but
       since  gob  does  not C parsing it needs them to figure out where the C
       code ends.  The code will be inserted into the init method,  above  the
       user  defined  body.   So  for example the following will initialize an
       integer to -1 and a string with a newly allocated string of "hello".

         public int foo = -1;
         private char *bar = {g_strdup("hello")};

       Automatic Destruction:

       Most data stored as pointers needs to have a function called  when  the
       object is finalized to either free the data.  Gob will let you define a
       function to be called on the data the object  is  finalized.   This  is
       achieved by putting ´destroywith´ followed by a function name after the
       variable definition.  It is only called if the data you defined this on
       is  not  NULL,  so you cans specify functions which do not handle NULL.
       It is very much like the GDestroyNotify function used in GTK+ and  glib
       in  many  places.   Unlike  many other places, gob will not enforce any
       kind of type safety here so be a little bit more careful.  Any function
       you  give  it  will be called as a "void function(void *)".  It will in
       fact be cast into such a form before called.  This is to avoid spurious
       warnings  for gtk calls to subclass methods.  The function needs not be
       of that form exactly, it just has to take one  argument  which  is  the
       pointer  to  the  data.   You  should  also not define this on any non-
       pointer data as the results may be undefined.  Example:

         public char *foo = {g_strdup("bar")}
                 destroywith g_free;

       Note that the function name you give must be a real  function  and  not
       macro.   Also  note that this is always called in the "finalize" method
       of GObject.  It is always called after any user  defined  body  of  the
       finalize handler.

       Sometimes  you  may  want  to run arbitrary code on destruction.  While
       this can be perfectly well done in the finalize handler.  Depending  on
       the  style  you may want to include all destruction/initialization code
       together with the definition of the data member.  Thus you may want  to
       put  arbitrary  code  which  will  then be inserted into the "finalize"
       method of GObject.   This  can  be  done  with  the  "destroy"  keyword
       followed  by  arbitrary code in curly braces.  Inside this code a macro
       called VAR will be define  which  refers  to  your  variable.   So  for
       example  destroying  a GString can be either done with a helper routine
       or the following code:

         public GString *string = {g_string_new(NULL)}
                 destroy {
                      if(VAR) g_string_free(VAR, TRUE);

       The thing to remember with these is that there are many ways to do this
       and  you´d  better  be consistent in your code in how you use the above
       things.  Also defining a helper routine that will  do  the  destruction
       will  be  a  nicer  thing to do if that´s a possibility.  The "destroy"
       keyword with code does take up more space in the file and it may become
       more cluttered.

       The  data  is  zeroed  out  after  being  destroyed.   This  is to make
       debugging easier in case your code  might  try  to  access  an  already
       finalized  object.   In  case  you have overridden the finalize method,
       your code will be run first and  only  then  will  the  destructors  be
       called.  You should not however make any assumptions about the order at
       which the  destructors  are  called.   If  you  have  interdependencies
       between  destructors  for  different  data members, you will have to do
       this in your own finalize override function.

       Automatic Unreffing:

       This is very much like the automatic destruction, but is instead run in
       the  dispose method (it is among other places called from the "destroy"
       method of GtkObject).  All data and other  objects  that  you  need  to
       unref should be done here, and not at finalize time.  The semantics are
       otherwise the same as for the  "destroywith"  and  "destroy"  keywords,
       except that you use "unrefwith" and "unref".

         public G:Object *foo = NULL
                 unrefwith g_object_unref;
         public G:Object *bar = NULL
                 unref {
                 g_object_unref (VAR);


       The  fourth  type of a data member a property type.  It is a named data
       member which is one of the features of the  GObject  system.   It  just
       defines  a  way  to get and set some data, but you have to take care of
       storing that data somewhere.  So it is normal to  also  have  a  normal
       private  (or  public)  data  member where you store the real data.  You
       normally need to define a get and a set handler.  They are fragments of
       C  code  that  will  be  used  to get the value or set the value of the
       argument.  Inside them you can use the define VAL to which  you  assign
       the  data or get the data.  You should treat this VAL as a GValue which
       stores the data of the correct type.  You can also use  the  identifier
       "self"  as  pointer to the object instance.  The type is defined as one
       of the GObject type enums, but without the G_TYPE_ prefix.   There  are
       also  some attributes of a property which you can set.  For example the
       following is a definition of an integer property ´height´ which will be
       synchronized  with  a  private  integer  data  member  also of the name

         private int height;
         property INT height
                (nick = _("Short nickname"),
                 blurb = _("Long description"),
                 minimum = 10,
                 maximum = 200,
                 default_value = 100)
               set { self->_priv->height = g_value_get_int (VAL); }
               get { g_value_set_int (VAL, self->_priv->height); };

       The attributes are really optional though you should at least set  some
       of  them.  All property types have a ´nick´ and a ´blurb´ attribute and
       you should set those accordingly.  This will make runtime querying  the
       object  nicer  as  things such as gui editors and class browsers can be
       more verbose about the class itself.  You  can  use  the  ´_("string")´
       notation  instead  of  just "string", and that will mark the string for

       Almost all types also have a ´default_value´ attribute which  sets  the
       initial  value  of  this  property  (on  object initialization, the set
       handler will be run automatically with this value).  This value will be
       overridden  if  the  user  sets a value of this property on the call to

       All the numeric types (including CHAR)  have  ´minimum´  and  ´maximum´
       attributes  which  can restrict the range.  If you do not specify these
       the range will be the full range that the data type can handle.

       Types such as UNICHAR and BOOLEAN only have  the  ´nick´,  ´blurb´  and
       ´default_value´ attributes.

       The  ENUM  type has an ´enum_type´ attribute which is the exact type of
       the enum.  This is so that the property knows which exact type you  can
       set,  rather then just knowing it is an enum.  You should always create
       an enum type specific for the enum itself  (see  section  on  the  enum

       Similarly  FLAGS  type has a ´flags_type´ which again you should set to
       the specific type of this flags data member.

       There is a  STRING  type  which  has  only  the  extra  ´default_value´

       The OBJECT type is one of the types that doesn´t have a ´default_value´
       and it only has an ´object_type´ attribute (in  addition  to  nick  and
       blurb  of  course)  that  is  the  exact object type that this property
       accepts.  The object_type should be as a  type,  that  is  for  example

       There is a BOXED type which is a pointer which has a boxed type defined
       (such that GObject knows how to copy and destroy this  pointer).   Here
       you  will  need to specify the ´boxed_type´ attribute with the specific
       type of the boxed pointer.

       There is also a POINTER type, which has only  the  ´nick´  and  ´blurb´
       attributes.   This  is  for  storing arbitrary pointers.  You should be
       careful with this one, as GObject knows nothing about the  data  stored
       at this pointer.  It is somewhat like a ´void *´ type.

       There is also the PARAM type for storing parameters with a ´param_type´

       You should notice that this list  is  pretty  much  like  the  list  of
       g_param_spec_* functions from gobject/gparamspecs.h, and the attributes
       are like the arguments of those functions.   Note  however  that  value
       array is NOT supported yet.

       You  can  also specify extra flags, such as CONSTRUCT or CONSTRUCT_ONLY
       using the ´flags´ attribute.  You can specify multiple flags  by  oring
       them  together  with  ´|´.   These  flags correspond to the GParamFlags
       enumeration except do not include the G_PARAM_ prefix.  So for  example
       to  define an enumeration property, which is a CONSTRUCT_ONLY property,
       we could do the following:

         private SomeEnumerationType foo;
         property ENUM foo
                (nick = _("Short nickname"),
                 blurb = _("Long description"),
                 enum_type = Some:Enumeration:Type
                 default_value = SOME_ENUMERATION_VALUE,
                 flags = CONSTRUCT_ONLY,

       The above example also gives an  example  of  automatic  linking  to  a
       standard  data  memember.   By including the attribute ´link´ a get and
       set handlers will be automatically added without having to type them by
       hand.   This  is  useful  for  a vast majority data types that are just
       linked to some standard data member and do  not  need  to  do  anything
       extra on get or set.

       Another extra feature of properties is the possibility of automatically
       exporing methods to get and set the property.  That is  without  having
       to  use  g_object_set  and g_object_get.  This is achieved by adding an
       ´export´ attribute to the list of property attributes.

       If you  do  not  define  a  set  or  get  handler,  the  property  will
       automatically be only readable or writable as appropriate.

       Gob2  also  creates  macros  which  can be used for type safe access to
       properties through  g_object_set  and  g_object_get.   The  macros  are
       called  <type>_PROP_<argument  name>(x)  and  <type>_GET_PROP_<argument
       name>(x).  They define both the  string  and  the  value  part  of  the
       argument.   So  for  setting  an argument of height, one would use (for
       object type My:Object):

         g_object_set (G_OBJECT (object),
                 MY_OBJECT_PROP_HEIGHT (7),

       And for getting, you would use:

         int height;
         g_object_get (G_OBJECT (object),
                 MY_OBJECT_GET_PROP_HEIGHT (&height),

       Note however that the type  safety  only  works  completely  on  GNU  C
       compilers.   The  code will compile on other compilers but with minimal
       type safety.  For complete type safety it is useful to use the  get/set
       methods that are defined by using the ´export´ attribute.

       To  get  bettery  type  safety  on  some of the property types, you can
       specify the ´type´ attribute which will add casts where appropriate  in
       code dealing with this property.  This is especially useful for POINTER
       and OBJECT types.  But even for others.

       You can also override properties from parent objects (that is  override
       their  implementation,  not  their  attributes).  Do this by adding the
       special ´override´ attribute.  For example if the parent object  had  a
       ´height´ property then you could override it by

         private int height;
         property INT height
               set { self->_priv->height = g_value_get_int (VAL); }
               get { g_value_set_int (VAL, self->_priv->height); };

       Overriding is supported since gob 2.0.10.


       There  is  a  whole  array  of  possible  methods.   The  three normal,
       "familiar" method types are private, protected and public.  Public  are
       defined  as  normal  functions  with  a  prototype  in the header file.
       Protected methods are defined as normal methods  (which  you  can  call
       from  other files), but their prototype is placed in the private header
       file.  Private methods are defined as static functions with  prototypes
       at the top of the .c file.  Then there are signal, virtual and override
       methods.  More on those later.  You can also define init and class_init
       methods  with  a  special  definition  if  you  want to add code to the
       constructors or you can just leave them out.  You can also not define a
       body  for  a  method,  by  just using ´;´ instead of a body.  This will
       define an empty function.  You  can´t  do  this  for  non-void  regular
       public, private or protected methods, however it is acceptable for non-
       void virtual, signal and override methods.

       Function argument lists:

       For all but the init and class_init  methods,  you  use  the  following
       syntax for arguments.  The first argument can be just "self", which gob
       will translate into a pointer to the object instance.  The rest of  the
       arguments  are  very similar to normal C arguments.  If the typename is
       an object pointer you should use the  syntax  defined  above  with  the
       words separated by ´:´
       <type> <argument id>
       <type> <argument id> (check <list of checks>)

       The  checks  are  glib  type  preconditions,  and can be the following:
       "null", which tests pointers for being NULL, "type" which  checks  GTK+
       object pointers for being the right type, "<test> <number>" which tests
       numeric arguments for being  a  certain  value.   The  test  can  be  a
       <,>,<=,>= != or ==.  Example:

         public int
         foo (self,
              int h (check > 0 < 11),
              Gtk:Widget *w (check null type))

       This  will  be  the prototype of a function which has a self pointer as
       the first argument, an integer argument which will be checked  and  has
       to be more then 0 and less then 11, and a pointer to a GtkWidget object
       instance and it is checked for being null and the  type  will  also  be

       Function attributes:

       For  method that aren’t virtual, signal or override methods, and aren’t
       init or  class_init,  GLib  function  attribute  macros  G_GNUC_PRINTF,
       G_GNUC_SCANF,  and  G_GNUC_FORMAT  can optionally be included after the
       argument list.  Simply include an ´attr´ keyword  and  the  C  code  to
       include  in  the  file.  You have to include braces and anything inside
       the braces will be printed into the  header  file  after  the  function
       declaration  and  before the trailing semicolon.  The braces themselves
       are not printed.  For example:

         public void
         print (self, const char *format (check null), ...)
           attr {G_GNUC_PRINTF(2, 3)}

       This will produce a prototype which will generate a warning at  compile
       time  if the contents of the format argument (argument number 2) aren’t
       consistent with  the  types  and  number  of  the  subsequent  variadic
       arguments  (the  first of which is argument number 3).  Only one ´attr´
       keyword per method is allowed.  If you have more than one attribute  to
       include, you should put them all within the braces.  Note that function
       attributes were aded in version 2.0.16.

       Error return:

       Methods which have a return value,  there  also  has  to  be  something
       returned  if  there  is an error, such as if a precondition is not met.
       The default is 0, casted to the type of the method.   If  you  need  to
       return  something  else then you can specify an ´onerror´ keyword after
       the prototype and any optional function  attribute  macros,  and  after
       that  a  number, a token (an identifier) or a bit of C code enclosed in
       braces {}.  The braces will not be printed into the output,  they  just
       delimit the string.  For example:

         public void * get_something (self, int i (check >= 0)) onerror NULL {

       The  onerror  value is also used in overrides that have a return value,
       in case there isn´t a parent method,  PARENT_HANDLER  will  return  it.
       More about this later.

       Default return:

       Some  signal  and virtual methods have a return type.  But what happens
       if there is no default handler and no one connects to a  signal.   GOB2
       will  normally  have  the  wrappers  return  whatever  you specify with
       onerror or ´0´ if you haven´t specified anything.  You can also specify
       a  default  return  value  with  the  keyword ´defreturn´.  It´s use is
       identical to the use of onerror, and you can in fact use  both  at  the
       same time.  Example

         virtual int get_some_int (self) onerror -1 defreturn 10 ;

       That  is an empty virtual method (in C++ terms a pure virtual).  If you
       never specify any handler for it in the derived children it  will  just
       return 10.

       Constructor methods:

       There  are  two methods that handle the construction of an object, init
       and class_init.  You define them by just using the init  or  class_init
       keyword  with  an  untyped argument in the argument list.  The argument
       will be usable in your function as a pointer to your  object  or  class
       depending if it´s init or class_init.  For example:

         init (self) {
                 /* initialize the object here */
                 self->a = 9;
                 self->b = 9;

         class_init (class) {
                 /* initialize the class, this is rarely needed */
                 class->blah = NULL;

       The  class_init  function  is  very rarely needed as all standard class
       initialization is taken care of  for  you  by  gob  itself.   The  init
       function  should  on  the  other  hand  be  used  whenever  you need to
       construct or initialize anything in the object to put it  into  a  sane

       Constructor, dispose, finalize methods:

       Since 2.0.16, you can also easily add code to the object’s constructor,
       dispose, and finalize methods.  See GObject documentation on how  these
       are  run.   The  code  you  add  will be run before calling the parents
       function for dispose and finalize, and after the  parent  function  for
       constructor.   The  syntax  is  just  like  init  and  class_init.  For

         constructor (self) {
            /* constructor method */

         dispose (self) {
            /* dispose method */

         finalize (self) {
            /* finalize method */

       You can also just override those methods as usual,  but  the  above  is
       much easier and nearly as flexible.

       Virtual methods:

       Virtual  methods are basically pointers in the class structure, so that
       one can override the method in derived methods.  That is  to  implement
       the  method  in  a  derived class, you must then use an override method
       (more on those later).  They can be empty (if you put  ´;´  instead  of
       the  C  code).   A wrapper will also be defined which makes calling the
       methods he same as public methods.  This  type  of  method  is  just  a
       little  bit "slower" then normal functions, but not as slow as signals.
       You define them by using "virtual" keyword before  the  prototype.   If
       you  put  the  keyword "private" right after the "virtual" keyword, the
       wrapper will not be a public method, but a private one.  You can do the
       same with "protected" to make a protected wrapper.


       Signals  are  methods  to  which  the  user can bind other handlers and
       override the default handler.  The default  handler  is  basically  the
       method  body.  This is the most versatile and flexible type of a method
       and also the slowest.  You need to specify a whole bunch of things when
       you  define  a  signal.   One thing is when the default handler will be
       run, first or last.  You specify that by "first" or "last" right  after
       the  "signal"  keyword.  Then you need to define the GObject enum types
       (again without the G_TYPE_ prefix).  For that  you  define  the  return
       types  and  the  types  of  arguments  after  the  "self"  pointer (not
       including the "self" pointer).  You put  it  in  the  following  syntax
       "<return type> (<list of arguments>)".  If the return type is void, the
       type should be "NONE", the same should be for the argument  list.   The
       rest  of the prototype is the same as for other method types.  The body
       can also be empty, and also there is a public method wrapper which  you
       can use for calling the signal just like a public method.  Example:

         signal first INT (POINTER, INT)
         int do_something (self, Gtk:Widget *w (check null type), int length)


         signal last NONE (NONE) void foo (self);

       If  you  don´t want the wrapper that emits the signal to be public, you
       can include the keyword "private" after  the  "signal"  keyword.   This
       will  make  the  wrapper  a normal private method.  You can also make a
       protected wrapper by using "protected" instead of "private".

       If you don´t define a "first" or a "last", the default will be taken as

       You  can  also  add  additional  flags.  You do this just like with the
       argument flags, although this is probably very  rare.   These  are  the
       G_SIGNAL_*  flags,  and  you  can add them without the G_SIGNAL_ prefix
       into a parenthesis, just after the "signal" keyword.   By  default  all
       public signals are G_SIGNAL_ACTION.

       Also  gob2  creates  a  wrapper  macros for typesafe signal connection.
       That is you will be warned by the compiler if you pass a callback  that
       is  not  the  correct prototype.  This will again only warn you on gcc,
       but it will compile without warning on another compiler.   So  as  with
       all  the  typesafety  hacks  in  gob, it is better to test your objects
       under gcc to get any  warnings  even  if  you  are  using  a  different
       compiler in the end.

       The methods that are created for you are:

         <class_name>_connect__<signal_name> (<object>, <callback>, <data>)
         <class_name>_connect_after__<signal_name> (<object>, <callback>, <data>)
         <class_name>_connect_data__<signal_name> (<object>, <callback>, <data>,
                                                   <destroy_notify>, <flags>)

       These    three    functions   correspond   to   the   g_signal_connect,
       g_signal_connect_after and  g_signal_connect_data  functions  that  you
       would  normally  use,  except  they are for a specific signal.  Also do
       note the two underscores between the method name and the  signal  name.
       For example to connect the signal "foo" on the object "Test:Object" you
       would do:

         test_object_connect__foo (object, callback, data);

       To use BOXED in the signal arguments you need to tell gob which type of
       boxed   argument   you  want  to  use.   For  this  you  can  just  add
       BOXED_GTK_TYPE_STRING    instead     of     BOXED.      For     example
       BOXED_GTK_TYPE_TREE_ITER  for  GtkTreeIter.   This  works since version

       Override methods:

       If you need to override some method (a signal or a  virtual  method  of
       some  class  in  the parent tree of the new object), you can define and
       override method.  After the "override"  keyword,  you  should  put  the
       typename  of  the  class  you are overriding a method from.  Other then
       that it is the same as for other methods.  The "self" pointer  in  this
       case  should  be  the type of the method you are overriding so that you
       don´t get warnings during compilation.  Also to call the method of  the
       parent class, you can use the PARENT_HANDLER macro with your arguments.

         override (Gtk:Container) void
         add (Gtk:Container *self (check null type), Gtk:Widget *wid (check null type))
                 /* some code here */
                 PARENT_HANDLER(self, wid);

       If  the  function  has  a  return  value,  then  PARENT_HANDLER  is  an
       expression  that  you  can  use.   It  will  return whatever the parent
       handler returned, or the "onerror" expression if there  was  no  parent

       Method names:

       Inside  the  code,  aliases  are set for the methods, so that you don´t
       have to type the class name before each call, just type  self_  instead
       of  the  name of the class.  So to call a method called blah, you would
       use the name self_blah.  Example:

         private int
         foo (self)
              return self->len;

         private int
         bar (self, int i)
              return self_foo (self) + i;


       You should define a new method which should be a normal public  method.
       Inside  this  method, you can use the GET_NEW macro that is defined for
       you and that will fetch a new object, so a fairly standard  new  method
       would look like:

         public GObject *
         new (void) {
              GObject *ret = GET_NEW;
              return G_OBJECT (ret);

       You  should  not  a  subtle peculiarity of the GObject system here.  If
       there is any code inside the  G_OBJECT  macro  argument,  it  will  get
       executed   multiple   times.    This   means   that   things   such  as
       G_OBJECT(GET_NEW) would actually create 4 objects, leaking 3  of  them.
       A good rule (as with anywhere in C) is to be careful with all macros.


       Self alias casts:

       There  are  some  standard casts defined for you.  Instead of using the
       full macros  inside  the  .c  file,  you  can  use  SELF,  IS_SELF  and
       SELF_CLASS.   Using  these  makes it easier to for example change class
       names around.

       Self alias types:

       There are also the Self and SelfClass types inside your .c file.  These
       serve  the  same function as the above, they make it easier to type and
       easier  to  change  typenames  around  which  can  help  a  lot  during
       prototyping  stage.   However you should note that the Self type should
       not be used in function prototypes as one of  the  arguments  or  as  a
       return value type.  This is because this is a simple C typedef which is
       only available inside your .c file and not in the  header  files.   You
       can  disable  both the self casting macros and the self type aliases by
       passing --no-self-alias to gob.



       In your generated C file, you can  use  the  defines  GOB_VERSION_MAJOR
       GOB_VERSION_MINOR and GOB_VERSION_PATCHLEVEL if you wish to for example
       use a feature that is only available in some newer gob  version.   Note
       however  that  you can only use these defines in the C code portions of
       your .gob file, and #ifdef´s cannot span multiple functions.  Check the
       BUGS section for more on using the C preprocessor and gob.

       Minimum version requires:

       You  can  also  make your .gob file require at least certain version of
       gob.  You do this by putting  ´requires  x.y.z´  (where  x.y.z  is  the
       version  number)  outside of any C block, comment or class, usually you
       should make this the first line in the file or close to  the  top.   If
       gob finds this and the version of gob used to compile the code is lower
       then that listed in the require, gob will generate an error  and  exit.
       For  example  to  require  that gob2 version 2.0.0 or higher be used to
       compile a file, put this at the top of that file:

         requires 2.0.0


       You can create new GObject ENUM, FLAGS and GError types for use in your
       classes  easily.   Glib  includes  some  utilities  for handling these,
       however it may be cleaner to  use  the  below  specified  way  in  your
       classes.   It  also then doesn´t require any Makefile setup.  Make sure
       this is defined in the same section as the class, that is not in any of
       the ´%?{´ ´%}´ sections.

       You  use  the  keywords ´enum´ ´flags´ and ´error´ as you would use the
       ´class´ keyword.  Then  you  give  a  prefix  for  the  values  in  the
       enumeration.   Then  you  define  a list of values just like in C.  For
       ´enum´ types you can also specify the values assigned to  each  string.
       Then  you  specify  the  type  in  the standard gob style of specifying
       types.  Here are a few examples of all of these:

         enum LAME_CLIENT {
               NONE = 9,
         } Test:Enum;

         flags BUGA_BUGA {
         } Some:Flags;

         error TEST_OBJECT_ERROR {
         } Test:Object:Error;

       This will for  example  define  an  enum  that  is  equivalent  to  the
       following C code:

         typedef enum {
               LAME_CLIENT_NONE = 9,
         } TestEnum;


       There  is  a  C++ mode so that gob creates C++ compiler friendly files.
       You need to use the --for-cpp argument to  gob.   This  will  make  the
       generated file have a .cc instead of a .c extension, and several things
       will be adjusted to make it all work for a  C++  compiler.   One  thing
       that  will  be  missing  is an alias to the new method, as that clashes
       with C++, so instead you´ll have to use the full  name  of  the  method
       inside  your  code.   Also note that gob does not use any C++ features,
       this option will just make  the  generated  code  compile  with  a  C++


       The  get_type  is not really a method, but a function which initializes
       your object.  Recently objects appeared which require  you  to  make  a
       custom get_type function.  So it is possible to override this function.
       To do so, just define a new public  method  called  get_type,  with  no
       arguments.  Example:

         public GType
         get_type (void)
            /* code goes here */
            return some_type;


       Currently  gob  will  only  allow you to implement interfaces (that is,
       define new classes which implement an interface) and doesn´t  yet  have
       support  for  making  new  interfaces,  but this will be coming at some
       point in the future.

       To define a class  that  implements  an  interface  add  a  class  flag
       ´interface´  with  the type name of the interface as an argument.  Then
       to implement a specific method of the interface,  just  add  ´interface
       <typename>´ before the method definition.  The method can, and probably
       should be, private.

       The following example implements a  new  object,  that  implements  the
       Gtk:Tree:Model  interface  and  implements the get_flags method of that
       interface.  Do note that except for standard (GTK+ and  glib)  specific
       interfaces  which  seem  to  have a non-standard name for the interface
       structure, the  structure  should  end  with  and  Iface,  if  you  are
       implementing an interface.  That is for example for the Gtk:Tree:Model,
       the  structure  containing  the  table  of  methods  should  be   named
         class Some:Object from G:Object
                 (interface Gtk:Tree:Model)
                 /* function implemented for the Gtk:Tree:Model interface */
                 interface Gtk:Tree:Model
                 private GtkTreeModelFlags
                 get_flags (Gtk:Tree:Model *self (check null type))
                      /* Here would be the implementation */
                      return (GtkTreeModelFlags)0;

       If  you want to implement multiple interfaces just list more class flag
       lines as follows:

         class Some:Object from G:Object
                 (interface Gtk:Tree:Model)
                 (interface Gtk:Editable)
                 /* ... */


       If you want to build a BonoboObject class gob2 has direct  support  for
       these.  Just create a new object that derives from Bonobo:Object.  Then
       use a "BonoboObject" class flag with the interface name as an argument.
       The  interface  name  should be as you would type it in C, that is with
       underscores as namespace separators.  Then you add the  methods  (using
       exact  same  names as in the idl file) and prepend those methods with a
       BonoboObject keyword.   For  example  imagine  you  have  an  interface
       GNOME/Foo/SomeInterface,  with  a  method  fooBar  that  takes a single

         class Foo:Some:Interface from Bonobo:Object
           (BonoboObject GNOME_Foo_SomeInterface) {

                 private void
                 fooBar (PortableServer_Servant servant,
                         const CORBA_char *string,
                         CORBA_Environment *ev)
                         Self *self = SELF (bonobo_object_from_servant (servant));

                         /* your code here */

                 /* rest of class */

       Note that the implementation method can  be  private,  in  fact  that´s
       probably  a  good  idea to do.  It won´t work to make this a signal, it
       can however be a virtual.  Note that the method  prototype  must  match
       the  one  from  the  interface  header  file,  or  you  will  get a bad
       assignment warning.  You should check  the  header  file  generated  by
       orbit-idl  and  see the epv structure for the correct prototypes if you
       can´t figure them out from the idl itself.  Also note  that  the  first
       argument   is   not   "self",   but   the  servant  and  you  must  use
       bonobo_object_from_servant function to get the actual object pointer.


       Gob can simplify writing a libglade class.  Just create  a  new  object
       that  derives  from a GtkContainer widget.  Then use a "GladeXML" class
       flag with the glade file name, root  widget  and  optional  domain   as
       arguments between double quotes.  For example:

       class My:Glade from Gtk:Window (GladeXML "" "root")

       Note  however  that  then  "" would have to be in the
       current directory.  You could specify a path, but that may not work for
       all  installations.  You can replace the glade filename with a token to
       be used in the generated .c file and you can then have a macro with the
       filename, as follows:

       class My:Glade from Gtk:Window (GladeXML GLADE_FILE "root")

       And somewhere in your header files you would have

       #define GLADE_FILE "/path/to/"

       You  can  declare widgets as data members by adding a ’GladeXML’ to the

       private Gtk:Button * button1 GladeXML;

       This will automatically set the "button1" from the GladeXML file.

       All signals created with  glade  are  automatically  connected  if  you
       defined  those  class  methods  in  your class.  For example suppose in
       glade  that  we  set  the  "connect"  signal  on  button1  to   go   to
       on_button1_clicked, then in our gob file we can just write:

       public void
       on_button1_clicked(self, GtkButton * button)

       See  the examples directory for a full example.  Note that this feature
       requires version at least 2.0.12.


       Gob will need to define some  local  variables  and  functions  in  the
       generated  files,  so  you need to take some precaution not to conflict
       with these.  The general rule of thumb is that all of these start  with
       three  underscores.  There is one, "parent_class" which doesn´t because
       it´s intended for use in your  code.   For  virtuals  or  signals,  you
       cannot  use  the  identifier __parent__ which is used for the parent of
       the object.  You should actually never access __parent__ either  as  it
       not  guaranteed  that it will stay named this way.  Data members cannot
       be named __parent__  nor  _priv.   For  methods,  you  cannot  use  the
       identifiers  "init"  or  "class_init"  unless  you mean the constructor
       methods.  You shouldn´t generally use 3 underscores  even  in  override
       method  argument  lists and virtual and signal method names as it might
       confuse the PARENT_HANDLER macro.  In  fact  avoiding  all  names  with
       three underscores is the best policy when working with gob.

       There  are a couple of defines which you shouldn´t be redefining in the
       code or other headers.  These are SELF, IS_SELF, SELF_CLASS, SELF_TYPE,

       As for types, there are Self and SelfClass types which are only defined
       in  your  source  files.  Their generation (just like the generation of
       the SELF macros) can be turned off, see command line options.


       If you want to use gtk-doc style inline documentation for your objects,
       you  can  do  one  of  two things.  First, you could include the inline
       documentation comments in your %{ %} section which  will  then  be  put
       verbatim  into  the output source file.  This is the way you should use
       for functions you define outside of the class.

       For class methods, you should use a gtk+ style comment, however it  can
       be  indented  any  number  of  tabs or spaces and you can use the short
       method name without the type prefix.  Gob  will  automatically  try  to
       extract  these  and  translate to full names and put them in the output
       source file.  An example would be:

         class Gtk:Button:Example from Gtk:Button {
                  * new:
                  * Makes a new #GtkButtonExample widget
                  * Returns: a new widget
                 GtkWidget *
                         return (GtkWidget *)GET_NEW;

       If the function you are documenting is a signal or a  virtual  then  it
       will  be  documenting  the wrapper that starts that virtual function or
       emits that signal.


       Sometimes you may need to use  an  object  of  type  MyObjectA  in  the
       MyObjectB  class  and  vice versa.  Obviously you can´t include headers
       for both.  So you need to just declare the typedef in the header  of  A
       for B, and the other way around as well.  The headers generated include
       a protecting define before it declares the typedef.  This define is the
       __TYPEDEF_<upper  case  object  name>__.  So inside my-object-a.h there
       will be this:

         #ifndef __TYPEDEF_MY_OBJECT_A__
         #define __TYPEDEF_MY_OBJECT_A__
         typedef struct _MyObjectA MyObjectA;

       Now instead  of  including  my-object-a.h  in  the  header  section  of
       my-object-b.gob,  just  copy  the  above  code there and you´re set for
       using MyObjectA as a type in the method parameters and public types.

       Another way to get out of this problem is if you can  use  those  types
       only  in  the  private  members,  in  which  case  they won´t be in the
       generated public header.


       If you are using normal makefiles, what you need to  do  is  to  add  a
       generic rule for .gob files.  So you would include the following in the
       Makefile and then just use the .c and .h files as usual (make sure  the
       space before the ´gob2´ is a tab, not spaces):

         %.c %.h %-private.h: %.gob
                 gob2 $<


       This is a little bit more involved.  Basically the first thing to do is
       to check for GOB2 in your file.  You can use the  supplied
       m4  macro  which  will  also  check  the version of gob.  Basically you
       include this:


       This will replace @GOB2@ in your makefiles with the full path of  gob2.
       Thus  when  adding the generic rule to your file, it should
       look like:

         %.c %.h %-private.h: %.gob
                 @GOB2@ $<

       For you have to set up a couple  more  things.   First  you
       have  to  include  the  generated  .c  and  .h files into BUILT_SOURCES
       variable.  You have to include both the .gob and the .c and .h files in
       the SOURCES for your program.


       When  nothing  has  changed  you  might  not  really  want  to  rebuild
       everything and gob  provides  options  --no-touch  (since  2.0.13)  and
       --no-touch-headers to avoid this.  When working with build systems such
       as automake you have to be more careful as just using those options can
       cause  automake to get confused and you will need to use something like
       the following:

         foo_SOURCES = foo.gob foo.gob.stamp foo.c foo.h foo-private.h
         BUILT_SOURCES = foo.gob.stamp
         MAINTAINERCLEANFILES = foo.gob.stamp

         %.gob.stamp: %.gob
                 @GOB2@ --no-touch $<
                 @touch $@


       GOB does several things to make debugging the code  easier.   First  it
       adds  preprocessor  commands  into  the output c file that point to the
       correct places in your .gob input file.  However sometimes there  might
       be  some  bigger  confusion and this is just not helpful.  In this case
       you will probably want to have gcc point you directly at the  generated
       files.   For  this  use the --no-lines command line option.  You should
       also note that these commands are not generated for the  public  header
       file  at  all.   If  there  is  an error which points you to the public
       header file, make sure you fix this error in the .gob  file,  otherwise
       your  changes will not have any effect after gob recompiles the sources

       Sometimes you might want to know which  method  you  are  in  for  some
       debugging  output.   GOB  will  define __GOB_FUNCTION__ macro, which is
       just a string constant with a pretty name of the method.


       It is possible to have your .gob file also preprocessed by m4.  This is
       useful  if  you  have  a  lot  of  files  and  you´d  like to have some
       preprocessor put in some common features.  All you have to  do  is  add
       --m4  to  the  command  line  of gob2 and gob2 will first run your file
       through m4.  You can print the directory that is searched for m4  files
       by running "gob2 --m4-dir"

       All  the arguments after --m4 will be passed to m4 itself, so it has to
       be the last gob2 argument on  the  command  line.   This  way  you  can
       specify arbitrary options to pass to m4.


       The  lexer  does  not  actually parse the C code, so I´m sure that some
       corner cases or maybe even some not so corner cases of C  syntax  might
       confuse gob completely.  If you find any, send me the source that makes
       it go gaga and I´ll try to make the lexer try to  handle  it  properly,
       but no promises.

       Another  thing  is  that  gob  ignores  preprocessor macros.  Since gob
       counts braces, the following code won´t work:

         #ifdef SOME_DEFINE
         if(foo) {
         if(bar) {

       To make this work, you´d have to do this:

         #ifdef SOME_DEFINE

       There is no real good way we can handle this without parsing C code, so
       we  probably never will.  In the future, I might add #if 0 as a comment
       but that´s about as far as I can  really  take  it  and  even  that  is
       problematic.   Basically,  if  you  use  gob,  just  don´t  use  the  C
       preprocessor too extensively.  And if you use it make sure that you  do
       not cross the boundaries of the C code segments.

       Comments  will  not  get through to the generated files unless inside C
       code.  This is not the  case  for  gtk-doc  style  comments  which  are

       The  short  name  aliases  are  actually  implemented  as  pointers  to
       functions.  Thus if you want to get the pointer of a function using the
       short name alias you can´t use the ´&´.  Thus:

         void (*foo)(Self *);

         /* this will NOT work */
         foo = &self_short_name;

         /* this will work */
         foo = self_short_name;

         /* Both of these will work */
         foo = &my_class_long_name;
         foo = my_class_long_name;


       George Lebl <>

       GOB2 Homepage:

                                  GOB2 2.0.17