1.17.02.53 MOD conversion vs FX commands

[Harbinger]

Full Version:
OpenMPT v1.17.2.53

Has the bug occured in previous versions? If yes, please specify version(s): (This option is optional, and doesn't need research. But in case you know...) Not sure.


Description of the bug: Found this while converting an IT file to MOD to test volume commands. Was warned about converting "down" to MOD format in dialog, but MPT changed IT's Vxx command to XM's Gxx command (both are Global Volume settings), but Gxx is not an official MOD command. It did set the Global Volume however. When saving as MPT MOD (did not test Compatible Export), the Gxx commands disappeared.
IMO either file conversion should not apply unequivalent commands, or the conversion should not be allowed (and perhaps explained why not in a dialog window).

How often does it happen?: Always.

How to reproduce (step by step description): Open an IT track (it may work with other formats). Make sure there are Global Volume commands; for IT, this would be Vxx. Go to Song Properties and change the format to MOD. A dialog will open reminding you that you lose some information -- fair enough. After the conversion, the Vxx commands will be changed to Gxx commands, which shouldn't be allowed in MOD format. It works, but is not saved.

[Saga Musix]

The converter does not remove most of the unusable formats because this gives the author a chance to fix them (although admittedly, he has to know what works and what doesn't with the new format). The mod conversion will be much better in the next version, but if anyone else finds this behavior annoying / irritating / whatever, please tell me and I will consider removing invalid commands.

[LPChip]

Although I will not use this functionality, I plead for removing it. It works more confusing rather than good, and if you want to keep it, at least change the warning box to explain that it is not right.

I would've blindly trusted OpenMPT to make a good conversion, then close OpenMPT to find out that my song is now screwed up.

[g]

I'm going to be a PITA and suggest to make it optional. I.e. "remove invalid commands? Y/N".

[bvanoudtshoorn]

Maybe it's worth highlighting dodgy commands with a red background or something to make them obvious to the user.

[Harbinger]

I would opt for a warning dialog showing what commands will be altered/deleted, with the chance to back out of the conversion one last chance.

[Saga Musix]

Please confirm that this has been fixed in OpenMPT 1.18 release candidate. You can set the thread status to S=C yourself then.