GOB \- The GTK+ Object Builder
.SH SYNOPSIS
.PP
-.B gob [-?] [-h] [-w] [--exit-on-warn] [--no-exit-on-warn] [--for-cpp]
-[--no-touch-headers] file
+.B gob [-?] [-h] [--help] [--version] [-w] [--exit-on-warn]
+[--no-exit-on-warn] [--for-cpp] [--no-gnu] [--always-private-header]
+[--no-private-header] [--no-touch-headers] file
.SH DESCRIPTION
.PP
GTK+ Object Builder is a simple preprocessor for easily creating
.B -?
.TP
.B -h
+.TP
+.B --help
Display a simple help screen.
.TP
+.B --version
+Display version information (note, --version was not added until 0.92.0)
+.TP
.B -w
.TP
.B --exit-on-warn
-Exit with an errorcode even when you encounter a warning.
+Exit with an error code even when you encounter a warning.
.TP
.B --no-exit-on-warn
Exit with an error only on errors, not on warnings, this is the default.
.B --for-cpp
Generate C++ code.
.TP
+.B --no-extern-c
+Never add the extern "C" to the header.
+.TP
+.B --no-gnu
+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)
+.TP
.B --no-touch-headers
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.
-
+so it is not enabled by default. Private header is still touched even if
+unchanged however.
+.TP
+.B --always-private-header
+Always create a \fB<basename>-private.h\fR file, even if it would be empty.
+Otherwise, it is only created when there are private data members in the class.
+This option implicitly negates --no-private-header
+.TP
+.B --no-private-header
+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. This option implicitly negates
+--always-private-header
.SH TYPENAMES
.PP
.PP
The filenames are created from the typename. The words are
separated by '-' 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.
-The header file is created to be human readable and to be used as a
+"Gtk:New:Button", the files are \fBgtk-new-button.c\fR and
+\fBgtk-new-button.h\fR.
+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 \fB<basename>-private.h\fR (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 editted by hand, and
+case of parsing errors. The output should not be edited by hand, and
you should only edit the .gob file.
.SH INCLUDING NORMAL C CODE IN THE OUTPUT FILES
.PP
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. To
-put the code in the output header file, start the code with a '%h{'.
-For example:
+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 \fIsections\fR 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. For example:
.nf
+ %headertop{
+ /* this will be on top of the public header */
+ %}
+
+ %privateheader{
+ /* this will go into the private header file */
+ %}
+
%h{
/* will be included in the header */
void somefunc(int i);
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 header.
+.PP
+If you made any data members private, gob will also create a source file
+that will be called \fB<basename>-private.h\fR. 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.
.SH MAKING A NEW CLASS
.PP
.PP
Data members:
.PP
-There are three types of data members. Two of them are normal
-data numbers, and one is a virtual one, usually linked to a normal public
-data member. The two normal data members are public or private. They are
-basically just copied into the object directly. There is only one
+There are four types of data members. Three of them are normal
+data numbers, and one is a virtual one, usually linked to a normal
+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:
.nf
public int i;
private GtkWidget *h;
+ protected long k;
.fi
.PP
-Public datamembers are accessed normally as members of the object struct.
-Example where 'i' is as above a public data member:
+Public and protected data members are accessed normally as members of
+the object struct. Example where 'i' is as above a public data member:
.nf
object->i = 1;
.fi
.PP
The private data members are defined in a structure which is only available
-inside the .c file. You must access them using the structure _priv. Example
+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):
.nf
object->_priv->h = NULL;
.fi
-Note that the _priv structure is only accessible to C code blocks below or
-inside the class definition in the .gob file. If you use it above, you will
-get a 'dereferencing incomplete pointer type' error from the C compiler.
+The _priv structure is defined in the \fB<basename>-private.h\fR.
+This file is automatically included if you don't include it yourself. You
+should always explicitly include it if you explicitly also include the main
+header file.
+.PP
+In case you use the \fB--no-private-header\fR option, no
+private header file is created and you can only access the _priv pointer
+below the class definition in the .gob file.
.PP
-The third type is an argument type. It is a named datamember which
+The fourth type is an argument type. It is a named data member which
is one of the features of the GTK+ object system. You 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
.fi
.PP
-If you don't define a set or a get handler it will be a readonly
-or a writeonly argument. If you want to add extra argument flags, add
+If you don't define a set or a get handler it will be a read-only
+or a write-only argument. If you want to add extra argument flags, add
them into parenthesis after the argument keyword, separated by '|' and
without the GTK_ARG_ prefix. For example:
.nf
public int height;
argument (CONSTRUCT) INT height get { ARG = self->height; };
+.fi
+This makes the argument settable even before the object is constructed, so
+that people can pass it to gtk_object_new function. Useful is also
+CONSTRUCT_ONLY flag which makes the argument only available during
+construction of the object.
+.PP
+Since 0.92.1, gob creates macros which can be used for type safe access to
+gtk arguments. The macros are called <type>_ARG_<argument name>(x) and
+<type>_GET_ARG_<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):
+.nf
+
+ gtk_object_set(GTK_OBJECT(object),
+ MY_OBJECT_ARG_HEIGHT(7),
+ NULL);
+
+.fi
+And for getting, you would use:
+.nf
+
+ int height;
+ gtk_object_set(GTK_OBJECT(object),
+ MY_OBJECT_GET_ARG_HEIGHT(&height),
+ NULL);
+
+.fi
+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.
+.PP
+To get good type safety on POINTER types however, you should specify
+an optional C type that gob should use. For other then POINTER types
+this is redundant but possible. To do this, place '(type <c type>)'
+right after the GTK+ type. Example:
+.nf
+
+ argument POINTER (type char *) foo set { /* foo */ } get { /* bar */ };
+
.fi
.PP
Methods:
.PP
-There is a whole array of possible methods. The two normal,
-"familiar" method types are private and public. Public are defined as
-normal functions with a prototype in the header file. Private methods
+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. You can also
-define init and init_class methods with a special definition if you want
+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.
.PP
Argument lists:
.PP
-For all but the init and init_class methods, you use the
+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
something else then you can specify an "onerror" keyword after the
prototype 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
+output, they just delimit the string. For example:
.nf
public void * get_something(self, int i (check >= 0)) onerror NULL {
}
.fi
+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.
+.PP
+Constructor methods:
+.PP
+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:
+.nf
+
+ init(object) {
+ /* initialize the object here */
+ object->a = 9;
+ object->b = 9;
+ }
+
+ class_init(class) {
+ /* initialize the class, this is rarely needed */
+ class->blah = NULL;
+ }
+
+.fi
+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 state. Sometimes you need
+some arguments, for this you should either use a construct method and a
+new function like many GTK+ widgets, and/or a CONSTRUCT or CONSTRUCT_ONLY
+type of an argument.
.PP
Virtual methods:
.PP
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"
+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.
.PP
Signals:
.PP
.fi
.PP
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.
+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".
.PP
If you don't define a "first" or a "last", the default will be taken as
"last".
}
.fi
+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 handler.
.PP
Calling methods:
.PP
}
.fi
+.PP
+
+.SH DEALING WITH DIFFERENT GOB VERSIONS
+.PP
+Defines:
+.PP
+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. Also note that these
+have only been available since the 0.92.1 version of gob.
+.PP
+Minimum version requires:
+.PP
+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 gob version 0.92.1 or higher
+be used to compile a file, put this at the top of that file:
+.nf
+
+ requires 0.92.1
+
+.fi
+It should be noted however that this feature was not added until 0.92.1, and
+so if the file gets compiled by a lower version, gob would generate a
+syntax error. Thus by putting in a requires line, you are implicitly
+requiring at least 0.92.1.
.SH C++ MODE
.PP
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 extention, and several things will be adjusted to
+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++ compiler.
+.SH IDENTIFIER CONFLICTS
+.PP
+Gob will need to define some local varibles 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.
+
+.SH DEALING WITH CIRCULAR HEADERS
+.PP
+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 since v0.92.2 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:
+.nf
+
+ #ifndef __TYPEDEF_MY_OBJECT_A__
+ #define __TYPEDEF_MY_OBJECT_A__
+ typedef struct _MyObjectA MyObjectA;
+ #endif
+
+.fi
+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.
+.PP
+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.
+
.SH BUGS
.PP
Also the lexer does not actually parse the C code, so I'm sure that some corner
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.
+.PP
+Comments will not get through to the generated files unless inside C code.
+This makes using something like gtk-doc harder. However I'm planning to
+fix this somehow.
.SH AUTHOR
.PP
projects / gob-dx.git / blobdiff