Ported Polygon->is_valid() and ExPolygon->is_valid()

xs/src/ExPolygon.cpp

@@ -40,6 +40,16 @@ ExPolygon::area() const
     return a;
 }
 
+bool
+ExPolygon::is_valid() const
+{
+    if (!this->contour.is_valid() || !this->contour.is_counter_clockwise()) return false;
+    for (Polygons::const_iterator it = this->holes.begin(); it != this->holes.end(); ++it) {
+        if (!(*it).is_valid() || (*it).is_counter_clockwise()) return false;
+    }
+    return true;
+}
+
 SV*
 ExPolygon::to_SV() {
     const unsigned int num_holes = this->holes.size();

xs/src/ExPolygon.hpp

@@ -20,6 +20,7 @@ class ExPolygon
     void translate(double x, double y);
     void rotate(double angle, Point* center);
     double area() const;
+    bool is_valid() const;
 };
 
 typedef std::vector<ExPolygon> ExPolygons;

xs/src/Polygon.cpp

@@ -92,4 +92,10 @@ Polygon::make_clockwise()
     return false;
 }
 
+bool
+Polygon::is_valid() const
+{
+    return this->points.size() >= 3;
+}
+
 }

xs/src/Polygon.hpp

@@ -20,6 +20,7 @@ class Polygon : public MultiPoint {
     bool is_counter_clockwise() const;
     bool make_counter_clockwise();
     bool make_clockwise();
+    bool is_valid() const;
 };
 
 typedef std::vector<Polygon> Polygons;

xs/t/04_expolygon.t

@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 20;
+use Test::More tests => 21;
 
 use constant PI => 4 * atan2(1, 1);
 
@@ -23,6 +23,7 @@ my $hole_in_square = [  # cw
 
 my $expolygon = Slic3r::ExPolygon->new($square, $hole_in_square);
 
+ok $expolygon->is_valid, 'is_valid';
 is ref($expolygon->pp), 'ARRAY', 'expolygon pp is unblessed';
 is_deeply $expolygon->pp, [$square, $hole_in_square], 'expolygon roundtrip';
 

xs/t/06_polygon.t

@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 12;
+use Test::More tests => 13;
 
 my $square = [  # ccw
     [100, 100],
@@ -14,6 +14,7 @@ my $square = [  # ccw
 ];
 
 my $polygon = Slic3r::Polygon->new(@$square);
+ok $polygon->is_valid, 'is_valid';
 is_deeply $polygon->pp, $square, 'polygon roundtrip';
 
 is ref($polygon->arrayref), 'ARRAY', 'polygon arrayref is unblessed';

xs/xsp/ExPolygon.xsp

@@ -20,6 +20,7 @@
     void scale(double factor);
     void translate(double x, double y);
     double area();
+    bool is_valid();
 %{
 
 ExPolygon*

xs/xsp/Polygon.xsp

@@ -27,6 +27,7 @@
     bool is_counter_clockwise();
     bool make_counter_clockwise();
     bool make_clockwise();
+    bool is_valid();
 %{
 
 Polygon*