Ruler (Canvas*, const Metric& m);
Ruler (Canvas*, const Metric& m, Rect const&);
Ruler (Item*, const Metric& m);
Ruler (Item*, const Metric& m, Rect const&);
Ruler (Canvas*, const Metric& m);
Ruler (Canvas*, const Metric& m, Rect const&);
Ruler (Item*, const Metric& m);
Ruler (Item*, const Metric& m, Rect const&);