GNOME Bugzilla – Bug 341378
G_DECLARE_TYPE pendant to G_DEFINE_TYPE
Last modified: 2014-12-22 18:00:20 UTC
It would be neat to have a G_DECLARE_TYPE pendant to G_DEFINE_TYPE. E.g. G_DECLARE_TYPE(gtk_handle_box) would expand to GType gtk_handle_box_get_type (void); So the _get_type() functions would be completely abstracted away and not just magically defined by using the macro in the .c file.
Not sure how useful this is when it is only a tiny fraction of the boilerplate you need in the header file. Sadly (*), you can't define macros from macros, so all the cast macros and so forth can't be handled in that way. (*) I say sadly, but then again, at other times I'm quite happy that the C preprocessor isn't any more complex than it is....
Created attachment 82071 [details] glib-declare-type script Well, such a macro would be usefull, if it also generate all the usefull but ugly casting macros: #define SOME_TYPE_CUSTOM_TYPE (some_custom_type_get_type()) #define SOME_CUSTOM_TYPE(obj) (G_TYPE_CHECK_INSTANCE_CAST(obj, SOME_TYPE_CUSTOM_TYPE, SomeCustomType)) #define SOME_CUSTOM_TYPE_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST(klass, SOME_TYPE_CUSTOM_TYPE, SomeCustomTypeClass)) #define SOME_IS_CUSTOM_TYPE(obj) (G_TYPE_CHECK_INSTANCE_TYPE(obj, SOME_TYPE_CUSTOM_TYPE)) #define SOME_IS_CUSTOM_TYPE_CLASS(obj) (G_TYPE_CHECK_CLASS_TYPE(obj, SOME_TYPE_CUSTOM_TYPE)) #define SOME_CUSTOM_TYPE_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS((obj), SOME_TYPE_CUSTOM_TYPE, SomeCustomTypeClass)) GType some_custom_type_get_type(); Well, as the preprocessor really is not capable of generating this, I'd suggest to ship a tool called "glib-declare-type" (or "glib-mktype", but I prefer the first name) with glib. A potential implementation would look like the attached script. Hope it's ok, that this script is implemented in Python, as other utilities shipped with GTK+ are written in Perl. The output of that script currently looks like this: $ glib-declare-type some custom_type #ifndef SOME_CUSTOM_TYPE_INCLUDED #define SOME_CUSTOM_TYPE_INCLUDED #include <glib-object.h> #define SOME_TYPE_CUSTOM_TYPE (some_custom_type_get_type()) #define SOME_CUSTOM_TYPE(obj) (G_TYPE_CHECK_INSTANCE_CAST(obj, SOME_TYPE_CUSTOM_TYPE, SomeCustomType)) #define SOME_CUSTOM_TYPE_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST(klass, SOME_TYPE_CUSTOM_TYPE, SomeCustomTypeClass)) #define SOME_IS_CUSTOM_TYPE(obj) (G_TYPE_CHECK_INSTANCE_TYPE(obj, SOME_TYPE_CUSTOM_TYPE)) #define SOME_IS_CUSTOM_TYPE_CLASS(obj) (G_TYPE_CHECK_CLASS_TYPE(obj, SOME_TYPE_CUSTOM_TYPE)) #define SOME_CUSTOM_TYPE_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS((obj), SOME_TYPE_CUSTOM_TYPE, SomeCustomTypeClass)) GType some_custom_type_get_type(); #endif // vim: et sta sw=4
duplicate of bug 653865 — which points to a more featureful generator for GObject boilerplate. also, there's bug 389585 — which adds a macro to generate the boilerplate similar to G_DEFINE_TYPE. *** This bug has been marked as a duplicate of bug 653865 ***