[3.7.0] Parameter Function Name - VST 3 Developer Portal

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[3.7.0] Parameter Function Name

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Introduction
Current defined function names
Example

Introduction

Edit controller component interface extension: Vst:: IParameterFunctionName.

[plug imp]
[extends Vst:: IEditController]
[released: 3.7.0]
[optional]

This interface allows the host to get a parameter associated to a specific meaning (a functionName) for a given unit. The host can use this information, for example, for drawing a Gain Reduction meter in its own UI. In order to get the plain value of this parameter, the host should use the Vst:: IEditController::normalizedParamToPlain. The host can automatically map parameters to dedicated UI controls, such as the wet-dry mix knob or the Randomize button. If a parameter provided by this interface is marked with the kReadOnly flag, the host should ignore this parameter.

Current defined function names

Name	Comment
Gain Reduction
kCompGainReduction
kCompGainReductionMax
kCompGainReductionPeakHold
kCompResetGainReductionMax
Randomize
kRandomize	Assigns randomized values across the full parameter range.
kRandomizeAroundCurrent	Assigns randomized values around the current parameter values (e.g. ±5% of the current value).
Panner
kPanPosCenterX	Gravity point X-axis [0, 1]=>[L-R] (for stereo: middle between left and right).
kPanPosCenterY	Gravity point Y-axis [0, 1]=>[Front-Rear].
kPanPosCenterZ	Gravity point Z-axis [0, 1]=>[Bottom-Top].
Other
kLowLatencyMode	Useful for live situation where low latency is required: 0 means LowLatency disable, 1 means LowLatency enable
kDryWetMix	Allowing to mix the original (Dry) Signal with the processed one (Wet): 0.0 means Dry Signal only, 0.5 means 50% Dry Signal + 50% Wet Signal, 1.0 means Wet Signal only

Example

In mycontroller.h

//------------------------------------------------------------------------
// here an example of how a VST 3 plug-in could support this IParameterFunctionName interface.
// we need to define somewhere the iids (in mycontroller.cpp):
  
#include "pluginterfaces/vst/ivstparameterfunctionname.h"

//in MyController class declaration
class MyController : public Vst::EditController, public Vst::IParameterFunctionName
{
    // ...
    tresult PLUGIN_API getParameterIDFromFunctionName (UnitID unitID, FIDString functionName,
                                                    Vst::ParamID& paramID) override;
    // ...
  
    OBJ_METHODS (MyController, Vst::EditController)
    DEFINE_INTERFACES
        // ...
        DEF_INTERFACE (Vst::IParameterFunctionName)
    END_DEFINE_INTERFACES (Vst::EditController)
    //...
}

In mycontroller.cpp

namespace Steinberg {
    namespace Vst {
        DEF_CLASS_IID (IParameterFunctionName)
    }
}
  
//------------------------------------------------------------------------
tresult PLUGIN_API MyController::getParameterIDFromFunctionName (UnitID unitID, FIDString functionName,
                                                                 Vst::ParamID& paramID)
{
    using namespace Vst;
  
    paramID = kNoParamId;
  
    if (unitID == kRootUnitId && FIDStringsEqual (functionName, kCompGainReduction))
        paramID = kMyGainReductionId;
  
    return (paramID != kNoParamId) ? kResultOk : kResultFalse;
}

Example of host implementation

if (auto functionName = Steinberg::U::cast<Vst::IParameterFunctionName> (mEditController->getIEditController ())
{
    Vst::ParamID paramID;
    if (functionName->getParameterIDFromFunctionName (Vst::FunctionNameType::kCompGainReduction, paramID) == kResultTrue)
    {
        // paramID could be cached for performance issue
        Vst::ParamValue norm = mEditController->getIEditController ()->getParamNormalized (paramID);
        Vst::ParamValue plain = mEditController->getIEditController ()->normalizedParamToPlain (paramID, norm);
        // plain is something like -6 (-6dB)
    }
}