Changed GTC file extension to SMLX

The GTC / GTCX file extension has been replaced by the (steel markup language).

In backward compatibility, the component will still recognize GTC / GTCX files.



The Export dialog contains the SMLX file format. Exports are only allowed with the new extension.



The Import dialog contains the following file formats: SMLX, GTCX and GTC.



Added global version information into SMLX files

Added a version to the SMLX file. It is written at the top of the file and it is an integer number.



If a newer version of the SMLX file is imported, an error message will appear and the file will not be imported.