Expose 2D polygon boolean operations in Geometry singleton

Clipper 6.4.2 is used internally to perform polypaths clipping, as well
as inflating/deflating polypaths. The following methods were added:

```
Geometry.merge_polygons_2d(poly_a, poly_b) # union
Geometry.clip_polygons_2d(poly_a, poly_b) # difference
Geometry.intersect_polygons_2d(poly_a, poly_b) # intersection
Geometry.exclude_polygons_2d(poly_a, poly_b) # xor

Geometry.clip_polyline_with_polygon_2d(poly_a, poly_b)
Geometry.intersect_polyline_with_polygon_2d(poly_a, poly_b)

Geometry.offset_polygon_2d(polygon, delta) # inflate/deflate
Geometry.offset_polyline_2d(polyline, delta) # returns polygons

// This one helps to implement CSG-like behaviour:
Geometry.transform_points_2d(points, transform)
```

All the methods return an array of polygons/polylines. The resulting
polygons could possibly be holes which could be checked with
`Geometry.is_polygon_clockwise()` which was exposed to scripting as well.

1 files changed, 39 insertions, 0 deletions

diff --git a/core/bind/core_bind.h b/core/bind/core_bind.h
index 2906de4a4a..561449f29e 100644
--- a/core/bind/core_bind.h
+++ b/core/bind/core_bind.h
@@ -402,15 +402,54 @@ public:
 	real_t segment_intersects_circle(const Vector2 &p_from, const Vector2 &p_to, const Vector2 &p_circle_pos, real_t p_circle_radius);
 	int get_uv84_normal_bit(const Vector3 &p_vector);
 
+	bool is_polygon_clockwise(const Vector<Vector2> &p_polygon);
 	Vector<int> triangulate_polygon(const Vector<Vector2> &p_polygon);
 	Vector<Point2> convex_hull_2d(const Vector<Point2> &p_points);
 	Vector<Vector3> clip_polygon(const Vector<Vector3> &p_points, const Plane &p_plane);
 
+	enum PolyBooleanOperation {
+		OPERATION_UNION,
+		OPERATION_DIFFERENCE,
+		OPERATION_INTERSECTION,
+		OPERATION_XOR
+	};
+	// 2D polygon boolean operations
+	Array merge_polygons_2d(const Vector<Vector2> &p_polygon_a, const Vector<Vector2> &p_polygon_b); // union (add)
+	Array clip_polygons_2d(const Vector<Vector2> &p_polygon_a, const Vector<Vector2> &p_polygon_b); // difference (subtract)
+	Array intersect_polygons_2d(const Vector<Vector2> &p_polygon_a, const Vector<Vector2> &p_polygon_b); // common area (multiply)
+	Array exclude_polygons_2d(const Vector<Vector2> &p_polygon_a, const Vector<Vector2> &p_polygon_b); // all but common area (xor)
+
+	// 2D polyline vs polygon operations
+	Array clip_polyline_with_polygon_2d(const Vector<Vector2> &p_polyline, const Vector<Vector2> &p_polygon); // cut
+	Array intersect_polyline_with_polygon_2d(const Vector<Vector2> &p_polyline, const Vector<Vector2> &p_polygon); // chop
+
+	// 2D offset polygons/polylines
+	enum PolyJoinType {
+		JOIN_SQUARE,
+		JOIN_ROUND,
+		JOIN_MITER
+	};
+	enum PolyEndType {
+		END_POLYGON,
+		END_JOINED,
+		END_BUTT,
+		END_SQUARE,
+		END_ROUND
+	};
+	Array offset_polygon_2d(const Vector<Vector2> &p_polygon, real_t p_delta, PolyJoinType p_join_type = JOIN_SQUARE);
+	Array offset_polyline_2d(const Vector<Vector2> &p_polygon, real_t p_delta, PolyJoinType p_join_type = JOIN_SQUARE, PolyEndType p_end_type = END_SQUARE);
+
+	Vector<Point2> transform_points_2d(const Vector<Point2> &p_points, const Transform2D &p_mat);
+
 	Dictionary make_atlas(const Vector<Size2> &p_rects);
 
 	_Geometry();
 };
 
+VARIANT_ENUM_CAST(_Geometry::PolyBooleanOperation);
+VARIANT_ENUM_CAST(_Geometry::PolyJoinType);
+VARIANT_ENUM_CAST(_Geometry::PolyEndType);
+
 class _File : public Reference {
 
 	GDCLASS(_File, Reference);