I tried to port a Python application with a custom TextBuffer serializer and deserializer to GTK+ 3 with introspection. But the introspection seems broken, so that the deserializer gets a number instead of a string, amongst other things:

1. TypeError: register_deserialize_format() takes exactly 4 arguments (3 given)

The C signature is: (GtkTextBuffer *buffer,
                     const gchar *mime_type,                                
                     GtkTextBufferDeserializeFunc function,
                     gpointer user_data,
                     GDestroyNotify user_data_destroy);

As such the function should take 3 arguments. Same for register_serialize_format()


2. Deserialize callback gets 7 arguments:

The argument types (in Python) are 'TextBuffer', 'TextBuffer', 'TextIter', 'int', 'long', 'bool', 'int'. The correct one would be:

'TextBuffer', 'TextBuffer', 'TextIter', string / array of characters, bool


based on the signature of the callback:

    GtkTextBuffer *register_buffer,
    GtkTextBuffer *content_buffer,
    GtkTextIter *iter,
    const guint8 *data,
    gsize length,
    gboolean create_tags,
    gpointer user_data,
    GError **error);

Bindings for Vala and Mono are broken too, they seem to ignore the '*' in the callback typedef, thus having a single char as the return value for the serializer, instead of an array of characters:

public delegate uchar TextBufferSerializeFunc (Gtk.TextBuffer register_buffer, Gtk.TextBuffer content_buffer, Gtk.TextIter start, Gtk.TextIter end, size_t length);

Vala also does not note that the length argument is a pointer to size_t. But those are probably other bugs caused somewhere in Vala (and Mono). I'm going to report this separately for Vala, I don't care about Mono, though.