if CANVAS_DEBUG is defined, then the env variable CANVAS_HARLEQUIN_DEBUGGING will...

[ardour.git] / libs / canvas / poly_line.cc

diff --git a/libs/canvas/poly_line.cc b/libs/canvas/poly_line.cc
index 2441e4e3dc4a31d771567b091132dc77a4b88994..60bca6bccf87011de9afbc28f6a12d679d49184f 100644 (file)
--- a/libs/canvas/poly_line.cc
+++ b/libs/canvas/poly_line.cc
@@ -17,15 +17,24 @@
     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;
 
-PolyLine::PolyLine (Group* parent)
-       : Item (parent)
-       , PolyItem (parent)
+PolyLine::PolyLine (Canvas* c)
+       : PolyItem (c)
+       , _threshold (1.0)
 {
+}
 
+PolyLine::PolyLine (Item* parent)
+       : PolyItem (parent)
+       , _threshold (1.0)
+{
 }
 
 void
@@ -41,7 +50,7 @@ PolyLine::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) cons
 bool
 PolyLine::covers (Duple const & point) const
 {
-       Duple p = canvas_to_item (point);
+       Duple p = window_to_item (point);
 
        const Points::size_type npoints = _points.size();
        
@@ -53,21 +62,44 @@ PolyLine::covers (Duple const & point) const
        Points::size_type j;
 
        /* repeat for each line segment */
-       
+
+       const Rect visible (window_to_item (_canvas->visible_area()));
+
        for (i = 1, j = 0; i < npoints; ++i, ++j) {
 
-               /* compute area of triangle computed by the two line points and the one
-                  we are being asked about. If zero (within a given tolerance), the
-                  points are co-linear and the argument is on the line.
+               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.
                */
-
-               double area = fabs (_points[j].x * (_points[j].y - p.y)) + 
-                                  (_points[i].x * (p.y - _points[j].y)) + 
-                                  (p.x * (_points[j].y - _points[i].y));
-               if (area < 0.001) {
+               
+               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) {
+                       continue;
+               }
+               
+               if (d < _threshold + _outline_width) {
                        return true;
                }
+               
        }
-
+       
        return false;
 }
+
+void
+PolyLine::set_covers_threshold (double t)
+{
+       _threshold = t;
+}