jtBaseApp/node_modules/@cesium/widgets/Source/Timeline/TimelineTrack.js

import { Color, defined, JulianDate } from "@cesium/engine";

/**
 * @private
 */
function TimelineTrack(interval, pixelHeight, color, backgroundColor) {
  this.interval = interval;
  this.height = pixelHeight;
  this.color = color || new Color(0.5, 0.5, 0.5, 1.0);
  this.backgroundColor = backgroundColor || new Color(0.0, 0.0, 0.0, 0.0);
}

TimelineTrack.prototype.render = function (context, renderState) {
  const startInterval = this.interval.start;
  const stopInterval = this.interval.stop;

  const spanStart = renderState.startJulian;
  const spanStop = JulianDate.addSeconds(
    renderState.startJulian,
    renderState.duration,
    new JulianDate()
  );

  if (
    JulianDate.lessThan(startInterval, spanStart) &&
    JulianDate.greaterThan(stopInterval, spanStop)
  ) {
    //The track takes up the entire visible span.
    context.fillStyle = this.color.toCssColorString();
    context.fillRect(0, renderState.y, renderState.timeBarWidth, this.height);
  } else if (
    JulianDate.lessThanOrEquals(startInterval, spanStop) &&
    JulianDate.greaterThanOrEquals(stopInterval, spanStart)
  ) {
    //The track only takes up some of the visible span, compute that span.
    let x;
    let start, stop;
    for (x = 0; x < renderState.timeBarWidth; ++x) {
      const currentTime = JulianDate.addSeconds(
        renderState.startJulian,
        (x / renderState.timeBarWidth) * renderState.duration,
        new JulianDate()
      );
      if (
        !defined(start) &&
        JulianDate.greaterThanOrEquals(currentTime, startInterval)
      ) {
        start = x;
      } else if (
        !defined(stop) &&
        JulianDate.greaterThanOrEquals(currentTime, stopInterval)
      ) {
        stop = x;
      }
    }

    context.fillStyle = this.backgroundColor.toCssColorString();
    context.fillRect(0, renderState.y, renderState.timeBarWidth, this.height);

    if (defined(start)) {
      if (!defined(stop)) {
        stop = renderState.timeBarWidth;
      }
      context.fillStyle = this.color.toCssColorString();
      context.fillRect(
        start,
        renderState.y,
        Math.max(stop - start, 1),
        this.height
      );
    }
  }
};
export default TimelineTrack;