Code review comment for lp:~robertcarr/mir/client-focus-notifications

352 + class Impediment
353 + {
354 + public:
355 + ~Impediment()
356 + {
357 + remove_callback();
358 + }
359 + protected:
360 + friend class CloggableEventSink;
361 + Impediment(std::function<void()> const& remove) :
362 + remove_callback(remove)
363 + {
364 + }
365 + private:
366 + std::function<void()> const remove_callback;
367 + };
368 +
369 + std::unique_ptr<Impediment> clog()
370 + {
371 + std::unique_lock<std::mutex> lg(lock);
372 + clogged = true;
373 +
374 + return std::unique_ptr<Impediment>(new Impediment(
375 + std::bind(std::mem_fn(&CloggableEventSink::unclog), this)));
376 + }

This approach seems complicated to me. C.f.

template<class Cloggee>
class Clogger
{
public:
    Clogger(Cloggee& cloggee) : cloggee{cloggee} { cloggee.clog(); }
    ~Clogger() { cloggee.unclog(); }
private:
    Cloggee& cloggee;
    Clogger(Clogger const&) = delete;
    Clogger& operator=(Clogger const&) = delete;
};