Some issues with the arpeggiator and the note sorting algorithms.

If you play an arpeggio over one note only, things generally work fine. There is the issue with occasionally dropped notes but if you use the function to skip notes and only arpeggiate over one note at a time, there is a chance that you will experience not a single glitch. If however you choose to arpeggiate over a chord, then you will most likely bump into a couple of the following issues.

Bug fixes/Basic functionality

• Skipped notes. Sometimes notes are skipped. (see picture below)
  Possibly related issue: Race condition in arpeggio processing #2606

• Extra notes. Sometimes an extra note is played at the end. Such an extra note can be the same as the actual note intended, increasing its volume. (see picture below)
  Fixed in: c39690d

Picture showing notes disappeared and extra notes added (as duplicates under the ordinary ones making them look bigger in this picture).
arpagain-01.mmp.zip

• The notes are only sorted after position and not after key. This is apparent in the arpeggiator when you're trying to arpeggiate over more than one key in Sort Mode. It's difficult to get the notes to follow a defined route. The common way is to start from the lowest note and then play the notes in order.
  Fixed in: 81966fa

• Sort mode. All notes are playing at the beginning of the notes. This is a regression from 1.1 and was introduced in 6650dd3.
  Fixed in 2d583db

• Sort mode. If the envelopes are off, the notes that should be silent are playing as ordinary notes while waiting for their turn. Solving this by using the same hack as the 'skip' algorithm as it had the same issue. Set as master note.
  Fixed in 6da8737

Internal changes

• Sorting notes is made both in Pattern::addNote(...) and in Pattern::rearrangeAllNotes(). The former is triggered on key 'on' and the latter on key 'off' but also works more generally on actions in the PianoRoll. The sort in Pattern::addNote(...) may thus be unnecessary. I've tested to drop this code and it seem to work just fine. Notes recorded through Midi keyboard are sorted only through Pattern::addNote so some rework seem to be needed to use Pattern::rearrangeAllNotes().
  Suggest: Wontfix.

• Pressing an existing note in the Piano Roll plays it back. When you release the key this triggers a note sort via Pattern::rearrangeAllNotes(): the same way as a drag/shift action. This even though nothing really has changed to the pattern. It may be a non issue as the extra cpu cycles involved doesn't appear to be screaming high.

Proposed functions

• Strict sync. Follow the quantized positions and don't play notes on key 'on'.
• Templates. Building templates in the Piano Roll and/or import Groove Templates.
• Convert a pattern played by the arpeggiator to notes in piano roll.