Method paintEvent

src/gui/StripChainWidget.cpp:342–521

}

void StripChainWidget::paintEvent(QPaintEvent*)
{
    rebuildLayout();

    QPainter p(this);
    p.setRenderHint(QPainter::Antialiasing, true);
    p.fillRect(rect(), AetherSDR::ThemeManager::instance().color("color.background.0"));

    if (m_boxes.isEmpty()) return;

    // Connector lines between adjacent boxes — handles three cases:
    //   - same row, both visual-left-to-right (even row)
    //   - same row, both visual-right-to-left (odd row)
    //   - row transition: a small L / U bend with a downward arrow
    auto drawArrowHead = [&](QPointF tip, QPointF from) {
        // Filled triangle pointing from `from` toward `tip`.
        const QPointF dir = tip - from;
        const qreal   len = std::hypot(dir.x(), dir.y());
        if (len < 0.01) return;
        const QPointF u(dir.x() / len, dir.y() / len);
        const QPointF perp(-u.y(), u.x());
        QPainterPath head;
        head.moveTo(tip);
        head.lineTo(tip.x() - u.x() * kArrowTip + perp.x() * kArrowTip,
                    tip.y() - u.y() * kArrowTip + perp.y() * kArrowTip);
        head.lineTo(tip.x() - u.x() * kArrowTip - perp.x() * kArrowTip,
                    tip.y() - u.y() * kArrowTip - perp.y() * kArrowTip);
        head.closeSubpath();
        p.setBrush(kConnector());
        p.setPen(Qt::NoPen);
        p.drawPath(head);
    };

    p.setPen(QPen(kConnector(), 2.0));
    for (int i = 0; i + 1 < m_boxes.size(); ++i) {
        const QRectF a = m_boxes[i].rect;
        const QRectF b = m_boxes[i + 1].rect;
        const bool sameRow = qFuzzyCompare(a.center().y(), b.center().y());
        if (sameRow) {
            // Horizontal connector — direction depends on row parity.
            // Even row: a is left, b is right → arrow into b's left edge.
            // Odd row: a is right, b is left → arrow into b's right edge.
            const bool rtl = a.center().x() > b.center().x();
            QPointF from, to;
            if (rtl) {
                from = QPointF(a.left(), a.center().y());
                to   = QPointF(b.right() + 1, b.center().y());
            } else {
                from = QPointF(a.right(), a.center().y());
                to   = QPointF(b.left() - 1, b.center().y());
            }
            p.setPen(QPen(kConnector(), 2.0));
            p.drawLine(from, to);
            drawArrowHead(to, from);
        } else {
            // Row transition — snake layout always turns at whichever
            // side of the widget the boxes currently occupy.  Compare
            // the box centre to the widget centre: right half → turn