Ported regular_points() to XS and renamed it to equally_spaced_points()

xs/src/Polygon.cpp

@@ -53,6 +53,15 @@ Polygon::split_at_first_point() const
     return this->split_at_index(0);
 }
 
+Points
+Polygon::equally_spaced_points(double distance) const
+{
+    Polyline* polyline = this->split_at_first_point();
+    Points pts = polyline->equally_spaced_points(distance);
+    delete polyline;
+    return pts;
+}
+
 double
 Polygon::area() const
 {

xs/src/Polygon.hpp

@@ -16,6 +16,7 @@ class Polygon : public MultiPoint {
     Polyline* split_at(const Point* point) const;
     Polyline* split_at_index(int index) const;
     Polyline* split_at_first_point() const;
+    Points equally_spaced_points(double distance) const;
     double area() const;
     bool is_counter_clockwise() const;
     bool is_clockwise() const;

xs/src/Polyline.cpp

@@ -49,6 +49,37 @@ Polyline::clip_start(double distance)
     if (this->points.size() >= 2) this->reverse();
 }
 
+/* this method returns a collection of points picked on the polygon contour
+   so that they are evenly spaced according to the input distance */
+Points
+Polyline::equally_spaced_points(double distance) const
+{
+    Points pts;
+    pts.push_back(*this->first_point());
+    double len = 0;
+    
+    for (Points::const_iterator it = this->points.begin() + 1; it != this->points.end(); ++it) {
+        double segment_length = it->distance_to(&*(it-1));
+        len += segment_length;
+        if (len < distance) continue;
+        
+        if (len == distance) {
+            pts.push_back(*it);
+            len = 0;
+            continue;
+        }
+        
+        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));
+        it--;
+        len = -take;
+    }
+    
+    return pts;
+}
+
+
 #ifdef SLIC3RXS
 SV*
 Polyline::to_SV_ref()

xs/src/Polyline.hpp

@@ -12,6 +12,7 @@ class Polyline : public MultiPoint {
     Lines lines() const;
     void clip_end(double distance);
     void clip_start(double distance);
+    Points equally_spaced_points(double distance) const;
     
     #ifdef SLIC3RXS
     SV* to_SV_ref();

xs/xsp/Polygon.xsp

@@ -23,6 +23,7 @@
         %code{% const char* CLASS = "Slic3r::Polyline"; RETVAL = THIS->split_at_index(index); %};
     Polyline* split_at_first_point()
         %code{% const char* CLASS = "Slic3r::Polyline"; RETVAL = THIS->split_at_first_point(); %};
+    Points equally_spaced_points(double distance);
     double length();
     double area();
     bool is_counter_clockwise();

xs/xsp/Polyline.xsp

@@ -23,6 +23,7 @@
         %code{% const char* CLASS = "Slic3r::Point"; RETVAL = THIS->first_point(); %};
     Point* last_point()
         %code{% const char* CLASS = "Slic3r::Point"; RETVAL = THIS->last_point(); %};
+    Points equally_spaced_points(double distance);
     double length();
     bool is_valid();
     void clip_end(double distance);