How to control the decimal places in a parameter added by ValueTree?

General JUCE discussion
1

I’ve been experimenting with the AudioProcessorValueTreeState for adding parameters in a plugin, and I’m wondering: If you have a float parameter, how do you specify the number of decimal places displayed, and how do you specify the increment value?

For example, I added a float parameter into a ValueTree initialization:

               std::make_unique<AudioParameterFloat> ("rep",            // parameterID
                                                       "Replications",            // parameter name
                                                       0.0f,              // minimum value
                                                       10.0f,              // maximum value
                                                       3.0f),             // default value

I want this parameter to display a single decimal place, and to increment by single decimal places, i.e. 0.1.

I tried:

    replicationsSlider.setNumDecimalPlacesToDisplay (1);

But it doesn’t have any effect. It still displays 2 decimal places and increments by 0.01.

2

There are two things, first, if you use the constructor, where you supply the NormalisableRange, you have much more control, e.g. step size and even logarithmic scales:

std::make_unique<AudioParameterFloat> ("rep",            // parameterID
                                       "Replications",                   // parameter name
                                       NormalisableRange<float> (0.0f,   // minimum value
                                                                10.0f,   // maximum value
                                                                 0.1f),  // step size
                                       3.0f),                            // default value
                                       String(),       // label
                                       AudioProcessorParameter::genericParameter,
                                       [](float value, int) { return String (value, 1); },
                                       [](const String& text) { return text.getFloatValue(); }

And furthermore you can add the lambdas for the number conversion. The SliderAttachment will propagate those to the Slider (and it probably overwrote your decimalsToDisplay settings)

1 Like
3

Try using NormalisableRange - intervalValue

NormalisableRange<<#typename ValueType#>>(<#ValueType rangeStart#>, <#ValueType rangeEnd#>, <#ValueType intervalValue#>, <#ValueType skewFactor#>)

like so:

auto normRange = NormalisableRange<float>(0.0f, 10.0f, 0.1f);
std::make_unique<AudioParameterFloat> ("rep",            // parameterID
                                       "Replications",            // parameter name
                                        normRange,
                                        3.0f),             // default value
4

Thanks, I appreciate the help!