diff -r 6de5ac1fb471 -r 3a9e761e4faa src/linetypes/subfilereference.h
--- a/src/linetypes/subfilereference.h	Sun Jan 19 14:25:57 2020 +0200
+++ b/src/linetypes/subfilereference.h	Wed Jan 22 00:23:29 2020 +0200
@@ -22,8 +22,10 @@
 	QString textRepresentation() const override;
 	void getPolygons(std::vector<gl::Polygon>& polygons, GetPolygonsContext* context) const override;
 	Point3D position() const;
+	void invert() override;
 private:
 	Model* resolve(DocumentManager* documents) const;
 	Matrix4x4 transformation;
 	QString referenceName;
+	bool isInverted = false;
 };