add Ruler to Canvas fwd.h

diff --git a/libs/canvas/canvas/fwd.h b/libs/canvas/canvas/fwd.h
index b8242e86bbf226d3689432460211154b1e87805c..728e6988d45fc30a4db10dcdfe76b7be0742077e 100644 (file)
--- a/libs/canvas/canvas/fwd.h
+++ b/libs/canvas/canvas/fwd.h
@@ -26,6 +26,7 @@ namespace ArdourCanvas {
        class Line;
         class LineSet;
        class Rectangle;
+        class Ruler;
        class Polygon;
        class PolyLine;
        class GtkCanvas;