For some formats, OpenMPT's loaders do some fixups to cater for automatic slide commands; most of the time this support breaks across any pattern boundaries, though. As yet another format is going to be added to this list (0001762), it really is about time to think about a better mechanism to support auto slides at runtime.

Formats and commands that need to be supported:

• ULT + XMF
  • Tone portamento (reset only by new note or tone portamento - not by porta up / down commands)
• 669
  • Portamento up / down, tone portamento (reset by any new command or note)
• STK
  • Some SoundTracker variants have automatic volume slides in addition to normal slides. They only continue as long as another effect is running on the same channel.
• FAR
  • Command 3 parameter indicates how many rows a slide should last.
  • Also has a similar weird volume slide.
• GMC
  • Portamento up / down
• STP
  • Portamento up / down (in addition to non-automatic variant, stopped by other portamentos but not tone portamento)
  • Fine portamento up / down (in addition to non-automatic variant, stopped by other portamentos but not tone portamento)
  • Tone portamento (stopped by parameter 0 or new note)
  • Fine volume slides (stopped by volume slides and Set Volume command or new note)
  • Global volume slide (stopped by Set Global Volume or parameter 0, NOT by new note)
  • Vibrato (stopped by parameter 0 or new note)
  • Tremolo (stopped by low nibble 0 or new note)
• Puma
  • Automatic portamento, but it stops at the end of the pattern and resets to the original note pitch

We need to investigate for each command which conditions reset the automatic command. For example, is auto tone portamento only reset by new notes or also by other pitch slides, or any other command?