void motion (double, double);
double component_to_parent_x (double x) const;
double parent_to_component_x (double x) const;
double component_to_parent_y (double y) const;
double parent_to_component_y (double y) const;
void motion (double, double);
double component_to_parent_x (double x) const;
double parent_to_component_x (double x) const;
double component_to_parent_y (double y) const;
double parent_to_component_y (double y) const;