terion/Source/ArcKnob.cpp

#include "ArcKnob.h"

ArcKnob::ArcKnob(juce::RangedAudioParameter& param)
    : juce::Slider(juce::Slider::RotaryHorizontalVerticalDrag,
                   juce::Slider::NoTextBox),
      parameter(param)
{
}

void ArcKnob::paint(juce::Graphics& g)
{
    auto bounds = getLocalBounds().toFloat();
    float diameter = juce::jmin(bounds.getWidth(), bounds.getHeight());
    float radius = diameter * 0.42f;
    float cx = bounds.getCentreX();
    float cy = bounds.getCentreY();

    const float startAngle = juce::MathConstants<float>::pi * 1.25f;
    const float endAngle = juce::MathConstants<float>::pi * 2.75f;
    const float angleRange = endAngle - startAngle;

    float rangeMin = static_cast<float>(getMinimum());
    float rangeMax = static_cast<float>(getMaximum());
    float value = static_cast<float>(getValue());
    float normalizedValue = (rangeMax > rangeMin)
                                ? juce::jlimit(0.0f, 1.0f, (value - rangeMin) / (rangeMax - rangeMin))
                                : 0.0f;
    float valueAngle = startAngle + normalizedValue * angleRange;

    // Background arc (dim)
    juce::Path bgArc;
    bgArc.addArc(cx - radius, cy - radius, radius * 2.0f, radius * 2.0f,
                 startAngle, endAngle, true);
    g.setColour(juce::Colour(0xff333340));
    g.strokePath(bgArc, juce::PathStrokeType(1.5f));

    // Value arc
    if (normalizedValue > 0.001f)
    {
        juce::Path valueArc;
        valueArc.addArc(cx - radius, cy - radius, radius * 2.0f, radius * 2.0f,
                         startAngle, valueAngle, true);
        g.setColour(juce::Colour(0xff7ecfcf));
        g.strokePath(valueArc, juce::PathStrokeType(1.5f));
    }

    // Center dot
    g.setColour(juce::Colour(0xff7ecfcf));
    g.fillEllipse(cx - 2.0f, cy - 2.0f, 4.0f, 4.0f);
}