Method renderTrajectoryPath

app/src/UI/Widgets/GPS.cpp:885–935

* @brief Renders the historical GPS trajectory polyline with tail-to-head gradient. */

 * @brief Renders the historical GPS trajectory polyline with tail-to-head gradient.
 */
void Widgets::GPS::renderTrajectoryPath(
  QPainter* painter, const QSize& view, int baseZoom, double scale, const QPointF& centerTileBase)
{
  const auto& series  = UI::Dashboard::instance().gpsSeries(m_index);
  const int tileSize  = 256;
  const double world  = qPow(2.0, baseZoom);
  const QPointF cTile = centerTileBase;

  auto project = [&](double lat, double lon) -> QPointF {
    QPointF tile = latLonToTile(lat, lon, baseZoom);

    double dx  = tile.x() - cTile.x();
    dx        -= std::round(dx / world) * world;

    QPointF delta(dx, tile.y() - cTile.y());
    return {view.width() * 0.5 + delta.x() * tileSize * scale,
            view.height() * 0.5 + delta.y() * tileSize * scale};
  };

  QVector<QPointF> path;
  auto pushIfValid = [&](double lat, double lon) {
    if (std::isnan(lat) || std::isnan(lon) || DSP::isZero(lat) || DSP::isZero(lon))
      return;

    path.append(project(lat, lon));
  };
  for (size_t i = 0; i < series.latitudes.size(); ++i)
    pushIfValid(series.latitudes[i], series.longitudes[i]);

  pushIfValid(m_latitude, m_longitude);

  const QRectF vp(0, 0, view.width(), view.height());
  const bool v =
    std::any_of(path.cbegin(), path.cend(), [&](const QPointF& p) { return vp.contains(p); });

  if (!v || path.size() <= 1)
    return;

  QLinearGradient grad(path.first(), path.last());
  grad.setColorAt(0.0, m_lineTailColor);
  grad.setColorAt(1.0, m_lineHeadColor);

  QPen pen(QBrush(grad), 2);
  painter->setPen(pen);

  for (int i = 1; i < path.size(); ++i) {
    const QPointF& p1 = path[i - 1];
    const QPointF& p2 = path[i];
    painter->drawLine(p1, p2);
  }
}

/**
 * @brief Renders the current-position indicator (halo, border, dot), wrapped 3x.