This accompanies the main
gtkmm merge requests at gtkmm#33 (closed)
This performs creation and manage()ment in a single step and therefore avoids the user having to write the discouraged new operator, looks more like Standard C++ things like make_shared(), etc. So, move our examples to it, and elaborate on why it is preferable to manage() or new/delete.
I got sidetracked and tacked on a subsequent commit that uses
auto a lot more, in the new code and elsewhere. I can split that if anyone want.