[Inkscape-devel] traits class specializations in header files

One of Peter's recent commits (moving Traits::TreeIterator<SPObject *> into a separate header file) started me thinking more about what should go in a separate header file and what shouldn't.

In _general_, I think "one class, one header" is the right approach, but some auxiliary classes (for example, traits specializations) have a more intimate relationship than most classes, and don't introduce any dependencies of their own.

Any thoughts on where a good place to draw the line might be, in general?

-mental