First naive prototype of seam painter

src/libslic3r/GCode.hpp

@@ -70,6 +70,15 @@ private:
 };
 
 
+struct CustomSeam {
+    std::vector<ExPolygons> enforcers;
+    std::vector<ExPolygons> blockers;
+
+    // Finds whether the point is inside an enforcer/blockers.
+    // Returns +1, 0 or -1.
+    int get_point_status(const Point& pt, size_t layer_id) const;
+};
+
 class OozePrevention {
 public:
     bool enable;
@@ -339,6 +348,9 @@ private:
     std::string     unretract() { return m_writer.unlift() + m_writer.unretract(); }
     std::string     set_extruder(unsigned int extruder_id, double print_z);
 
+    // Cache for custom seam enforcers/blockers for each layer.
+    CustomSeam                          m_custom_seam;
+
     /* Origin of print coordinates expressed in unscaled G-code coordinates.
        This affects the input arguments supplied to the extrude*() and travel_to()
        methods. */