Cabl client interface

[quasart]

Hello,
And first of all, thanks for your work :-)

I own a Maschine MK1 controler, it's a very nice hardware and I would love to use it more.
I found out your nice reverse-enginieering and abstraction project, and I'm looking forward trying your lib.
I'm reading the code now, and would like to share some feedbacks and enhancement proposals (enhancements I may develop myself)

I see two uses-cases for cabl :

1. Wanting to bind any controller like a gamepad (for example 4 buttons and 4 knobs), ignoring hardware labels

2. Making a music software.

• Labels on hardware are very convenient : "Volume" knob should control client volume on every device.
• On key pressed, client wants to know what note it was.

As a reminder, here is the current abstraction interface :

Client.h

  virtual void buttonChanged(Device::Button button_, bool buttonState_, bool shiftPressed_);
  virtual void encoderChanged(unsigned encoder_, bool valueIncreased_, bool shiftPressed_);
  virtual void keyChanged(unsigned index_, double value_, bool shiftPressed);
  virtual void controlChanged(unsigned pot_, double value_, bool shiftPressed);

My remarks:

1. First use case is impossible to implement properly :

• because Client developer doesn't know which Device::Button is available on actual user hardware.
• About knobs and key, client may choose to listen to knob 0. However, does abstraction guarantee that ids should be contiguous and starting at 0?

2. About 2nd use case:

• When pressing shift-Play, the client will observe Device::Button::Play, however shift-Play is labeled "Metronome" on Maschine MK1
• There is an enum for button but not for encoder (Client cannot know changed encoder is the one labeled "MainVolume" on the device)
• The Volume may be controlled by an encoder on some device and by a pot on others.

Proposed interface:

virtual  void  buttonChanged(  unsigned  button_,  bool    buttonState_,     bool  shiftPressed_, Device::Label label_ );
virtual  void  encoderChanged( unsigned  encoder_, bool    valueIncreased_,  bool  shiftPressed_, Device::Label label_ );
virtual  void  keyChanged(     unsigned  index_,   double  value_,           bool  shiftPressed_, Device::Label label_ );
virtual  void  controlChanged( unsigned  pot_,     double  value_,           bool  shiftPressed_, Device::Label label_ );

the button/knob parameters would be integers in range [0..NbOfButton[, [0..NbOfEncodor[, [0..NbOfControl[

Device::Label would be an enum with all common Labels. pressing shift would change label_ value (but not button id)

Key index_ could simply be value of a MIDI note. Device implementation should choose the best octave range, but we could required them to implement at least C4.

Unfortunately, this change is a serious interface break for legacy clients.

I hope I'm clear.
Let me know what you think about this analysis, if I'm missing something, if your plans are incompatible with this proposal, or if I should start coding :-)