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[3.6.12] MIDI Learn

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Introduction

MIDI Learn Interface: Vst:: IMidiLearn.

If this interface is implemented by the edit controller, the host will call this method whenever there is live MIDI-CC input for the plug-in. This way, the plug-in can change its MIDI-CC parameter mapping and inform the host via the Vst:: IComponentHandler::restartComponent with the kMidiCCAssignmentChanged flag. Use this if you want to implement custom MIDI-Learn functionality in your plug-in.

Example

In mycontroller.h

//------------------------------------------------------------------------
// here an example of how a VST 3 plug-in could support this IMidiLearn interface.
// we need to define somewhere the iids:
  
//in MyController class declaration
class MyController : public Vst::EditController, public Vst::IMidiLearn
{
    // ...
    //--- IMidiLearn ---------------------------------
    tresult PLUGIN_API onLiveMIDIControllerInput (int32 busIndex, int16 channel,
                                                  CtrlNumber midiCC) SMTG_OVERRIDE;
    // ...
  
    OBJ_METHODS (MyController, Vst::EditController)
    DEFINE_INTERFACES
        // ...
        DEF_INTERFACE (Vst::IMidiLearn)
    END_DEFINE_INTERFACES (Vst::EditController)
    //...
}

In mycontroller.cpp

#include "pluginterfaces/vst/ivstmidilearn.h
 
namespace Steinberg {
    namespace Vst {
        DEF_CLASS_IID (IMidiLearn)
    }
}
  
//------------------------------------------------------------------------
tresult PLUGIN_API MyController::onLiveMIDIControllerInput (int32 busIndex, int16 channel, CtrlNumber midiCC)
{
    // if we are not in doMIDILearn (triggered by a UI button for example) or wrong channel then return
    if (!doMIDILearn || busIndex != 0 || channel != 0 || midiLearnParamID == InvalidParamID)
        return kResultFalse;
 
    // adapt our internal MIDICC -> parameterID mapping
    midiCCMapping[midiCC] = midiLearnParamID;
 
    // new mapping then inform the host that our MIDI assignment has changed
    if (auto componentHandler = getComponentHandler ())
    {
        componentHandler->restartComponent (kMidiCCAssignmentChanged);
    }
    return kResultTrue;
}