Ported ExPolygon->area()

xs/src/ExPolygon.cpp

@@ -30,6 +30,16 @@ ExPolygon::rotate(double angle, Point* center)
     }
 }
 
+double
+ExPolygon::area() const
+{
+    double a = this->contour.area();
+    for (Polygons::const_iterator it = this->holes.begin(); it != this->holes.end(); ++it) {
+        a -= -(*it).area();  // holes have negative area
+    }
+    return a;
+}
+
 SV*
 ExPolygon::to_SV() {
     const unsigned int num_holes = this->holes.size();

xs/src/ExPolygon.hpp

@@ -19,6 +19,7 @@ class ExPolygon
     void scale(double factor);
     void translate(double x, double y);
     void rotate(double angle, Point* center);
+    double area() const;
 };
 
 typedef std::vector<ExPolygon> ExPolygons;

xs/src/Polygon.cpp

@@ -55,7 +55,7 @@ Polygon::split_at_first_point()
 }
 
 double
-Polygon::area()
+Polygon::area() const
 {
     ClipperLib::Polygon p;
     Slic3rPolygon_to_ClipperPolygon(*this, p);
@@ -63,7 +63,7 @@ Polygon::area()
 }
 
 bool
-Polygon::is_counter_clockwise()
+Polygon::is_counter_clockwise() const
 {
     ClipperLib::Polygon* p = new ClipperLib::Polygon();
     Slic3rPolygon_to_ClipperPolygon(*this, *p);

xs/src/Polygon.hpp

@@ -16,8 +16,8 @@ class Polygon : public MultiPoint {
     Polyline* split_at(const Point* point);
     Polyline* split_at_index(int index);
     Polyline* split_at_first_point();
-    double area();
-    bool is_counter_clockwise();
+    double area() const;
+    bool is_counter_clockwise() const;
     bool make_counter_clockwise();
     bool make_clockwise();
 };