Method emitRun

app/src/UI/Widgets/PlotCurve.cpp:560–610

* @brief Emits one run [start, start+len) as constant-width body quads with round joins: each * segment is a flat-capped quad extruded hw along its own normal (width never varies with * bend angle, sharp tips stay full-width), and each interior vertex gets an outer-side * round-join fan. Carries the previous direction across degenerate (zero-length) segments. */

 *        round-join fan. Carries the previous direction across degenerate (zero-length) segments.
 */
void Widgets::PlotCurve::emitRun(QSGGeometry::ColoredPoint2D* vertices,
                                 quint32* indices,
                                 int& v,
                                 int& idx,
                                 const QPointF* px,
                                 const qsizetype start,
                                 const qsizetype len,
                                 const double hw) const
{
  Q_ASSERT(vertices != nullptr);
  Q_ASSERT(indices != nullptr);
  Q_ASSERT(len >= 2);

  auto dirAt = [&](const qsizetype i, const QPointF& fallback) {
    QPointF dir = fallback;
    (void)unitDir(px[start + i], px[start + i + 1], dir);
    return dir;
  };

  QPointF prevDir = dirAt(0, QPointF(1, 0));
  for (qsizetype i = 0; i + 1 < len; ++i) {
    const QPointF dir = dirAt(i, prevDir);
    const QPointF n(-dir.y(), dir.x());

    const int body = v;
    emitCapSection(vertices, v, px[start + i], n, hw, m_color);
    emitCapSection(vertices, v, px[start + i + 1], n, hw, m_color);
    emitJoinIndices(indices, idx, body, body + 4);

    if (i + 2 < len) {
      const QPointF dOut = dirAt(i + 1, dir);
      const int nFan     = fanSegments(dir, dOut);
      if (nFan >= 1) {
        const double s = (dir.x() * dOut.y() - dir.y() * dOut.x()) < 0.0 ? 1.0 : -1.0;
        const QPointF nOut(-dOut.y(), dOut.x());
        emitFan(vertices,
                indices,
                v,
                idx,
                px[start + i + 1],
                QPointF(n.x() * s, n.y() * s),
                QPointF(nOut.x() * s, nOut.y() * s),
                nFan,
                hw,
                m_color);
      }
    }

    prevDir = dir;
  }
}

/**
 * @brief Rebuilds the ribbon node from the source series: project to pixels once, one