Forcing named return value optimization.
You want them to go first, but you also want to deduce them.
You can get a little bit of the way there.
Avoiding the need to invoke the operator explicitly as a specialized template, among other things.
Extending to std::weak_ptr.
Working out the boilerplate.
Assessing the state of affairs.
There are the obvious arguments, the non-obvious arguments, and the invisible arguments.
this pointer too late
Once destruction begins, strong references mean nothing.
You still need to filter to your window, so you don't mess up another window on the same thread.