Method paintEvent

src/gui/ClientCompKnob.cpp:237–356

}

void ClientCompKnob::paintEvent(QPaintEvent*)
{
    QPainter p(this);
    p.setRenderHint(QPainter::Antialiasing, true);

    const int w = width();
    const int h = height();
    // Center-label mode reclaims the 12-px label row above the ring.
    // The ring uses almost all remaining height — the 270° arc sweep
    // (225° → -45°) leaves a 90° gap at the bottom (4:30 → 7:30),
    // which is where the value readout lives.  Reserving a separate
    // "row" below the ring creates a visible gap; overlapping the
    // empty arc sector keeps the readout snug against the knob.
    const int topRow    = m_centerLabel ?  0 : 12;
    const int bottomRow = 4;
    const int diameter  = std::min(w - 4, h - topRow - bottomRow);
    const QRectF ring((w - diameter) * 0.5f,
                      static_cast<float>(topRow),
                      diameter, diameter);

    // Label — above the ring in classic mode, centred inside the
    // ring in center-label mode.  Centred text is rendered AFTER
    // the arc + pointer so it reads on top cleanly.
    QFont labelFont = p.font();
    labelFont.setPixelSize(9);
    labelFont.setBold(true);
    if (!m_centerLabel) {
        // Shrink-to-fit: longer labels ("Threshold", "Release") on
        // narrow knobs would otherwise truncate with "..." — scale
        // the font down in 1-px steps until the rendered width fits
        // the widget, floor at 7 px.
        int pixelSize = 9;
        QFontMetrics fm(labelFont);
        const float maxWidth = std::max(8.0f, static_cast<float>(w) - 2.0f);
        while (fm.horizontalAdvance(m_label) > maxWidth && pixelSize > 7) {
            --pixelSize;
            labelFont.setPixelSize(pixelSize);
            fm = QFontMetrics(labelFont);
        }
        p.setFont(labelFont);
        p.setPen(kLabelColor(this));
        p.drawText(QRectF(0, 0, w, 12), Qt::AlignCenter, m_label);
    }

    // Background ring.
    const qreal thick = std::max(2.0, diameter * 0.10);
    QPen bgPen(kRingBg(this), thick);
    bgPen.setCapStyle(Qt::FlatCap);
    p.setPen(bgPen);
    p.drawArc(ring.adjusted(thick * 0.5, thick * 0.5,
                            -thick * 0.5, -thick * 0.5),
              static_cast<int>(kArcStartDeg * 16.0f),
              static_cast<int>(kArcSpanDeg * 16.0f));

    // Value arc.
    QPen arcPen(kRingArc(this), thick);
    arcPen.setCapStyle(Qt::FlatCap);
    p.setPen(arcPen);