Editing the types file
If your library or application includes GObjects, you want their signals, arguments/parameters and position in the hierarchy to be shown in the documentation. All you need to do, is to list the xxx_get_type functions together with their include inside the <package>.types file.
#include <gtk/gtk.h> gtk_accel_label_get_type gtk_adjustment_get_type gtk_alignment_get_type gtk_arrow_get_type
Since GTK-Doc 1.8 gtkdoc-scan can generate this list for you. Just add "--rebuild-types" to SCAN_OPTIONS in Makefile.am. If you use this approach you should not dist the types file nor have it under version control.