Method _updateHash

modules/core/MapSystem.js:402–450

* _updateHash * Push changes in map state to the urlhash. * This gets called on 'draw', so fairly frequently

()

   * This gets called on 'draw', so fairly frequently
   */
  _updateHash() {
    const context = this.context;
    const scene = context.systems.gfx.scene;
    const urlhash = context.systems.urlhash;
    const viewport = context.viewport;

    // map
    const [lon, lat] = viewport.centerLoc();
    const transform = viewport.transform;
    const zoom = transform.zoom;
    // Why a '-' here?  Because "bearing" is the angle that the user points, not the angle that north points.
    const ang = numWrap(-transform.r * RAD2DEG, 0, 360);
    const precision = Math.max(0, Math.ceil(Math.log(zoom) / Math.LN2));
    const EPSILON = 0.1;

    const zoomStr = zoom.toFixed(2);
    const latStr = lat.toFixed(precision);
    const lonStr = lon.toFixed(precision);
    const angStr = ang.toFixed(1);  // degrees

    let val = `${zoomStr}/${latStr}/${lonStr}`;
    if (Math.abs(ang) > EPSILON) {
      val += `/${angStr}`;
    }

    urlhash.setParam('map', val);


    // note
    const layer = scene.layers.get('notes');
    let noteID;
    const [pair] = context.selectedData();  // get the first thing in the Map()
    const [datumID, datum] = pair || [];
    if (datum instanceof QAItem && datum.service === 'osm') {
      noteID = datumID;
    }

    // `note=true` -or- `note=<noteID>`
    if (layer?.enabled) {
      if (noteID) {
        urlhash.setParam('note', noteID);
      } else {
        urlhash.setParam('note', 'true');
      }
    } else {
      urlhash.setParam('note', null);
    }

  }


  /**