1 files changed, 56 insertions, 0 deletions
diff --git a/libs/canvas/poly_line.cc b/libs/canvas/poly_line.cc
index bdc4af9c10..7118e47555 100644
--- a/libs/canvas/poly_line.cc
+++ b/libs/canvas/poly_line.cc
@@ -17,7 +17,11 @@
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
+#include <algorithm>
+
 #include "canvas/poly_line.h"
+#include "canvas/canvas.h"
+#include "canvas/utils.h"
 
 using namespace ArdourCanvas;
 
@@ -37,3 +41,55 @@ PolyLine::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) cons
 		context->stroke ();
 	}
 }
+
+bool
+PolyLine::covers (Duple const & point) const
+{
+	Duple p = canvas_to_item (point);
+
+	const Points::size_type npoints = _points.size();
+	
+	if (npoints < 2) {
+		return false;
+	}
+
+	Points::size_type i;
+	Points::size_type j;
+
+	/* repeat for each line segment */
+
+	const Rect visible (_canvas->visible_area());
+	static const double threshold = 2.0;
+
+	for (i = 1, j = 0; i < npoints; ++i, ++j) {
+
+		Duple at;
+		double t;
+		Duple a (_points[j]);
+		Duple b (_points[i]);
+		
+		/*
+		  Clamp the line endpoints to the visible area of the canvas. If we do
+		  not do this, we may have a line segment extending to COORD_MAX and our
+		  math goes wrong.
+		*/
+		
+		a.x = std::min (a.x, visible.x1);
+		a.y = std::min (a.y, visible.y1);
+		b.x = std::min (b.x, visible.x1);
+		b.y = std::min (b.y, visible.y1);
+		
+		double d = distance_to_segment_squared (p, a, b, t, at);
+		
+		if (t < 0.0 || t > 1.0) {
+			return false;
+		}
+		
+		if (d < threshold) {
+			return true;
+		}
+		
+	}
+	
+	return false;
+}