Method RecursionGuard

gui/MainWindow.cxx:243–246

{
public:
  RecursionGuard(bool* lock) : lock{lock && !*lock ? lock : nullptr}
  {
    if (this->lock) *this->lock = true;
  }

  RecursionGuard(RecursionGuard&& other) : RecursionGuard{other.take()} {}
  ~RecursionGuard() { if (this->lock) *this->lock = false; }