efficient to add "fresh" stencils to what you're going to build.
* Do not create Stencil objects on the heap. That includes passing
- around Stencil* which are produced by Stencil::unsmob(). Either
+ around Stencil* which are produced by unsmob<Stencil>(). Either
copy Stencil objects, or use SCM references.
* Empty stencils have empty dimensions. If add_at_edge is used to