.\" .\" gob manual page .\" (C) 1999 George Lebl .\" .\" This manual page is covered by the terms of the GNU General .\" Public License. .\" .TH GOB 1 "GOB @VERSION@" .SH NAME 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 .SH DESCRIPTION .PP GTK+ Object Builder is a simple preprocessor for easily creating GTK+ objects. It does not parse any C code and ignores any C errors. It is in spirit similar to things like lex or yacc. .SH OPTIONS .PP .TP .B -? .TP .B -h Display a simple help screen. .TP .B -w .TP .B --exit-on-warn Exit with an errorcode 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. .TP .B --for-cpp Generate C++ code. .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. .TP .B --always-private-header Always create a \fB-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 datamembers, 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 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. .SH OUTPUT FILES .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 \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-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 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: .nf %h{ /* will be included in the header */ void somefunc(int i); %} %{ /* will be included in the C file */ void somefunc(int i) { /* some code */ } %} .fi .SH INCLUDE FILES .PP 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 header. .PP If you made any data members private, gob will also create a source file that will be called \fB-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 The class header: .PP 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 from { }". For example: .nf class Gtk:New:Button from Gtk:Button { } .fi .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 identifier allowed per typename unlike in normal C. Example: .nf public int i; private GtkWidget *h; .fi .PP Public datamembers 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 where 'h' is the private data member (as in the above example): .nf object->_priv->h = NULL; .fi Note that the _priv structure is defined in the \fB-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. 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 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 define ARG to which you assign the data or get the data. You can also use the identifier "self" as pointer to the object instance. The type is defined as one of the gtk type enums, but without the GTK_TYPE_ prefix. For example: .nf public int height; argument INT height set { self->height = ARG; } get { ARG = self->height; }; .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 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 .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 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 to add code to the constructors or you can just leave them out. .PP Argument lists: .PP For all but the init and init_class 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 ':' .nf or (check ) .fi .PP 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, " " which tests numeric arguments for being a certain value. The test can be a <,>,<=,>= != or ==. Example: .nf public int foo(self, int h (check > 0 < 11), Gtk:Widget *w (check null type)) .fi .PP 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 checked. .PP Error return: .PP 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 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 .nf public void * get_something(self, int i (check >= 0)) onerror NULL { ... } .fi .PP Virtual methods: .PP Virtual methods are basically pointers in the class structure, so that one can override the method in derived methods. 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. .PP Signals: .PP 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 gtk enum types (again without the GTK_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 " ()". 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: .nf signal first INT(POINTER,INT) int do_something(self, Gtk:Widget *w (check null type), int length) { ... } or signal last NONE(NONE) void foo(self); .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. .PP If you don't define a "first" or a "last", the default will be taken as "last". .PP Override methods: .PP 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. Example: .nf override (Gtk:Container) void add (Gtk:Container *self (check null type), Gtk:Widget *wid (check null type)) { /* some code here */ PARENT_HANDLER(self, wid); } .fi .PP Calling methods: .PP Inside the code, pointers are set for the methods, so that you don't have to type the class name before each call, just the name of the method. Example: .nf private int foo(self) { return self->len; } private int bar(self,int i) { return foo(self) + i; } .fi .PP Making new objects: .PP 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: .nf public GtkObject * new(void) { GtkObject *ret; ret = GTK_OBJECT (GET_NEW); return ret; } .fi .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 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 BUGS .PP Also 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. .PP Another thing is that gob ignores preprocessor macros. Since gob counts braces, the following code won't work: .nf #ifdef SOME_DEFINE if(foo) { #else if(bar) { #endif blah(); } .fi To make this work, you'd have to do this: .nf #ifdef SOME_DEFINE if(foo) #else if(bar) #endif { blah(); } .fi 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. .SH AUTHOR .PP George Lebl