Dear friend GrblGru,
It doesn't matter which version of DXF.
In the file “autocad_2012_pdf_dxf-reference_enu.pdf”, attached, look for the word “bulge”.
See attached a part of the source code.
See some references:
https://cambamcnc.com/forum/index.ph...49830#msg49830
https://cambamcnc.com/forum/index.ph...64299#msg64299