Generating the .defs files.
| Appendix G. Wrapping C Libraries with gmmproc |

## Generating the .defs files.

The `.defs` files are text files, in a lisp format, that describe the API of a C library, including its

- objects (GObjects, widgets, interfaces, boxed-types and plain structs)

- functions

- enums

- signals

- properties

- vfuncs

At the moment, we have separate tools for generating different parts of these `.defs`, so we split them up into separate files. For instance, in the `gtk/src` directory of the gtkmm sources, you will find these files:

`gtk.defs`

  Includes the other files.

`gtk_methods.defs`

  Objects and functions.

`gtk_enums.defs`

  Enumerations.

`gtk_signals.defs`

  Signals and properties.

`gtk_vfuncs.defs`

  vfuncs (function pointer member fields in structs), written by hand.

### Generating the methods .defs

This `.defs` file describes objects and their functions. It is generated by the h2def.py script which you can find in glibmm's `tools/defs_gen` directory. For instance,

    $ ./h2def.py /usr/include/gtk-3.0/gtk/*.h > gtk_methods.defs

### Generating the enums .defs

This `.defs` file describes enum types and their possible values. It is generated by the `enum.pl` script which you can find in glibmm's `tools` directory. For instance,

    $ ./enum.pl /usr/include/gtk-3.0/gtk/*.h > gtk_enums.defs

### Generating the signals and properties .defs

This `.defs` file describes signals and properties. It is generated by the special `extra_defs` utility that is in every wrapping project, such as `gtkmm/tools/extra_defs_gen/`. For instance

    $ cd tools/extra_defs_gen
    $ ./generate_extra_defs > gtk_signals.defs

You must edit the source code of your own `generate_extra_defs` tool in order to generate the `.defs` for the GObject C types that you wish to wrap. In the skeleton source tree, the source file is named `codegen/extradefs/generate_extra_defs_skeleton.cc`. If not done so already, the file should be renamed, with the basename of your new binding substituted for the `skeleton` placeholder. The `codegen/Makefile.am` file should also mention the new source filename.

Then edit the `.cc` file to specify the correct types. For instance, your `main()` function might look like this:

    #include <libsomething.h>

    int main(int, char**)
    {
      something_init();

      std::cout << get_defs(EXAMPLE_TYPE_SOMETHING)
                << get_defs(EXAMPLE_TYPE_THING);
      return 0;
    }

### Writing the vfuncs .defs

This `.defs` file describes virtual functions (vfuncs). It must be written by hand. There is no skeleton to start from. You can look at gtkmm's `gtk/src/gtk_vfuncs.defs` file.

Appendix G. Wrapping C Libraries with gmmproc |  | The .hg and .ccg files