I'd be careful exposing the tk canvas api from within Pd. It's a buggy interface, as evidenced by the off-by-one errors in the data-structure illustrations of Miller's book.
Hi Jonathan,
What do you mean by "exposing the tk canvas api" ? Is it about how I create GUI or about a specific object ? I made a lot of tests on Windows, Mac and Linux and it seems pretty stable. The fact is that I don't draw directly in the pd's canvas for many many reasons. You should have a look at the CICM wrapper.
Cheers