allow per-line configurability of the threshold used to determine if a PolyLine covers a given coordination

libs/canvas/canvas/poly_line.h

@@ -28,12 +28,21 @@ namespace ArdourCanvas {
 
 class LIBCANVAS_API PolyLine : public PolyItem
 {
-public:
+  public:
 	PolyLine (Group *);
-
+	
 	void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
-
+	
         bool covers (Duple const &) const;
+	/**
+	 * Set the distance at which a point will be considered to be covered
+	 * by the line. For the definition of "distance" see
+	 * utils.cc:distance_to_segment_squared()
+	 */
+	void set_covers_threshold (double);
+
+  private:
+	double _threshold;
 };
 	
 }

libs/canvas/poly_line.cc

@@ -28,6 +28,7 @@ using namespace ArdourCanvas;
 PolyLine::PolyLine (Group* parent)
 	: Item (parent)
 	, PolyItem (parent)
+	, _threshold (1.0)
 {
 
 }
@@ -59,7 +60,6 @@ PolyLine::covers (Duple const & point) const
 	/* 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) {
 
@@ -85,7 +85,7 @@ PolyLine::covers (Duple const & point) const
 			continue;
 		}
 		
-		if (d < threshold) {
+		if (d < _threshold + _outline_width) {
 			return true;
 		}
 		
@@ -93,3 +93,9 @@ PolyLine::covers (Duple const & point) const
 	
 	return false;
 }
+
+void
+PolyLine::set_covers_threshold (double t)
+{
+	_threshold = t;
+}