Ok, got a pair of CDJ-850s and out of curiosity, tested the deckadance remote control support. I mapped one deck to MIDI channel 10, one to channel 11.
+ Control CDs work as expected
- HID support obviously is just not implemented, but I guess this would be the best option in the long run
- MIDI support does not really work, see below
While I don't expect you to spend the time with HID support, at least MIDI support for CDJs would be nice to have. My findings about CDJ-850 MIDI and deckadance:
* Decks are correctly detected as separate units (different MIDI channels configured), as expected
* Buttons don't seem to send supported codes, for example play/pause is received but instead of stopping track when stopped, it fast-forwards ...
* Jog wheel seems to send different control codes for pitch (edge) and job (top), but I could only get it to adjust pitch, jog does not work
* Tempo slider value range is reversed, and deckadance does not have 'reverse slider values' function for midi sliders
Similar issues appear with my vestax VCI-100 (edge/jog can not be separately controlled), which is sending separate MIDI signals just fine for those controls. I guess the issue is combining the 'platter activated, sending jog data' commands handling? I guess fixing this with generic midi controller would require major changes to the deckadance MIDI mapping and control code, or at least the UI of these controls (I think your specialized controller support does more complicated things than the general mapping allows, so it seems like an UI issue, not framework issue?).
Did not really buy the CDJ's to control deckadance, so no great loss... I would just be happy if the MIDI/HID control would work, it might be handy sometimes.
If you need help for fixing these issues or adding at least rudimentary MIDI support for CDJ's (I guess 400 has similar issues?), I'm happy to collect you MIDI dumps from the various controls in the player and what they send in each use case, if you don't happen to have these players available. Of course, the most wonderful thing would be if you could team up with pioneer and officially create full CDJ HID support, bundling deckadance with the players
Anyway, this is not high priority request, please work on your current more important tasks and do this later if there is suitable time. Just wanted to report my findings if someone else is wondering about CDJ support.