Method countRun

app/src/UI/Widgets/PlotCurve.cpp:455–487

* @brief Counts one run's vertices and indices; the walk, direction fallback and fanSegments() * call MUST stay textually identical to emitRun or the passes disagree and overrun the * geometry buffer. qsizetype accumulators tolerate an undecimated raw series. */

 *        geometry buffer. qsizetype accumulators tolerate an undecimated raw series.
 */
void Widgets::PlotCurve::countRun(const QPointF* px,
                                  const qsizetype start,
                                  const qsizetype len,
                                  qsizetype& vertexCount,
                                  qsizetype& indexCount) const
{
  Q_ASSERT(px != 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);
    vertexCount       += 8;
    indexCount        += 18;

    if (i + 2 < len) {
      const QPointF dOut = dirAt(i + 1, dir);
      const int nFan     = fanSegments(dir, dOut);
      if (nFan >= 1) {
        vertexCount += 2 * nFan + 3;
        indexCount  += 9 * nFan;
      }
    }

    prevDir = dir;
  }
}

/**
 * @brief Counts ribbon vertices and indices over each visible run of two or more points, by