BTW, The SANE header is available here: http://anonscm.debian.org/gitweb/?p=sane/sane-backends.git;a=blob;f=include/sane/sane.h
And while doing this someone should try updating twain.h too: http://www.twain.org/devfiles/twain.h cheers, Pedro. (No it's not urgent, of course)
