http://bugs.winehq.org/show_bug.cgi?id=12464
--- Comment #12 from Dan Kegel dank@kegel.com 2012-05-30 12:59:10 CDT --- Created attachment 40341 --> http://bugs.winehq.org/attachment.cgi?id=40341 An old patch that does something similar
Here's an old patch from Jeff Miller that did something similar (though it uses gnome-open instead of xdg-open, maybe you'd want to try one and then the other).