Extend medial axis endpoints to fill the entire length. Includes fix for a minor memory leak caused by usage of old signature for Line::point_at()

xs/src/ExPolygon.cpp

@@ -148,6 +148,12 @@ ExPolygon::medial_axis(double max_width, double min_width, Polylines* polylines)
     // compute the Voronoi diagram
     ma.build(polylines);
     
+    // extend initial and final segments of each polyline (they will be clipped)
+    for (Polylines::iterator polyline = polylines->begin(); polyline != polylines->end(); ++polyline) {
+        polyline->extend_start(max_width);
+        polyline->extend_end(max_width);
+    }
+    
     // clip segments to our expolygon area
     intersection(*polylines, *this, *polylines);
 }

xs/src/Line.cpp

@@ -62,15 +62,22 @@ Line::midpoint() const
     return new Point ((this->a.x + this->b.x) / 2.0, (this->a.y + this->b.y) / 2.0);
 }
 
-Point*
-Line::point_at(double distance) const
+void
+Line::point_at(double distance, Point* point) const
 {
     double len = this->length();
-    Point* p = new Point(this->a);
+    *point = this->a;
     if (this->a.x != this->b.x)
-        p->x = this->a.x + (this->b.x - this->a.x) * distance / len;
+        point->x = this->a.x + (this->b.x - this->a.x) * distance / len;
     if (this->a.y != this->b.y)
-        p->y = this->a.y + (this->b.y - this->a.y) * distance / len;
+        point->y = this->a.y + (this->b.y - this->a.y) * distance / len;
+}
+
+Point
+Line::point_at(double distance) const
+{
+    Point p;
+    this->point_at(distance, &p);
     return p;
 }
 

xs/src/Line.hpp

@@ -25,7 +25,8 @@ class Line
     void reverse();
     double length() const;
     Point* midpoint() const;
-    Point* point_at(double distance) const;
+    void point_at(double distance, Point* point) const;
+    Point point_at(double distance) const;
     bool coincides_with(const Line* line) const;
     double distance_to(const Point* point) const;
     double atan2_() const;

xs/src/Polyline.cpp

@@ -43,7 +43,7 @@ Polyline::clip_end(double distance)
         }
         
         Line segment(last_point, *this->last_point());
-        this->points.push_back(*segment.point_at(distance));
+        this->points.push_back(segment.point_at(distance));
         distance = 0;
     }
 }
@@ -57,6 +57,23 @@ Polyline::clip_start(double distance)
     if (this->points.size() >= 2) this->reverse();
 }
 
+void
+Polyline::extend_end(double distance)
+{
+    // relocate last point by extending the last segment by the specified length
+    Line line(this->points[ this->points.size()-2 ], this->points.back());
+    this->points.pop_back();
+    this->points.push_back(line.point_at(line.length() + distance));
+}
+
+void
+Polyline::extend_start(double distance)
+{
+    // relocate first point by extending the first segment by the specified length
+    Line line(this->points[1], this->points.front());
+    this->points[0] = line.point_at(line.length() + distance);
+}
+
 /* this method returns a collection of points picked on the polygon contour
    so that they are evenly spaced according to the input distance */
 Points
@@ -79,7 +96,7 @@ Polyline::equally_spaced_points(double distance) const
         
         double take = segment_length - (len - distance);  // how much we take of this segment
         Line segment(*(it-1), *it);
-        pts.push_back(*segment.point_at(take));
+        pts.push_back(segment.point_at(take));
         it--;
         len = -take;
     }

xs/src/Polyline.hpp

@@ -16,6 +16,8 @@ class Polyline : public MultiPoint {
     Lines lines() const;
     void clip_end(double distance);
     void clip_start(double distance);
+    void extend_end(double distance);
+    void extend_start(double distance);
     Points equally_spaced_points(double distance) const;
     void simplify(double tolerance);
     

xs/t/09_polyline.t

@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 7;
+use Test::More tests => 10;
 
 my $points = [
     [100, 100],
@@ -42,4 +42,13 @@ is_deeply $polyline->pp, [ @$points, @$points ], 'append_polyline';
     is_deeply $polyline->pp, [ [0, 0], [50, 50], [125, -25], [150, 50] ], 'Douglas-Peucker';
 }
 
+{
+    my $polyline = Slic3r::Polyline->new(@$points);
+    is $polyline->length, 100*2, 'length';
+    $polyline->extend_end(50);
+    is $polyline->length, 100*2 + 50, 'extend_end';
+    $polyline->extend_start(50);
+    is $polyline->length, 100*2 + 50 + 50, 'extend_start';
+}
+
 __END__

xs/xsp/Line.xsp

@@ -26,7 +26,7 @@
     Point* midpoint()
          %code{% const char* CLASS = "Slic3r::Point"; RETVAL = THIS->midpoint(); %};
     Point* point_at(double distance)
-         %code{% const char* CLASS = "Slic3r::Point"; RETVAL = THIS->point_at(distance); %};
+         %code{% const char* CLASS = "Slic3r::Point"; RETVAL = new Point(THIS->point_at(distance)); %};
     Polyline* as_polyline()
         %code{% const char* CLASS = "Slic3r::Polyline"; RETVAL = new Polyline(*THIS); %};
 %{

xs/xsp/Polyline.xsp

@@ -29,6 +29,8 @@
     bool is_valid();
     void clip_end(double distance);
     void clip_start(double distance);
+    void extend_end(double distance);
+    void extend_start(double distance);
     void simplify(double tolerance);
 %{