Function getFitboundsLonRange

src/lib/geo_location_utils.js:419–445

* Pick a compact longitude range for `fitbounds`-style auto-framing when the * data straddles the antimeridian (±180°). * * Longitude is cyclic, so the naive [min, max] range used by the autorange * machinery can include a large empty span when points sit on both sides of * ±180° (e.g. lon = [1

(lons)

 *   more compact, otherwise null (caller keeps the autorange result).
 */
function getFitboundsLonRange(lons) {
    const sorted = lons.filter(isFinite).sort((a, b) => a - b);
    if (sorted.length < 2) return null;

    const n = sorted.length;
    const naiveSpan = sorted[n - 1] - sorted[0];
    // Data already wraps the whole globe; there is nothing to compact.
    if (naiveSpan >= 360) return null;

    // Widest gap between consecutive longitudes.
    let maxGap = -Infinity;
    let gapStart = -1;
    for (let i = 0; i < n - 1; i++) {
        const gap = sorted[i + 1] - sorted[i];
        if (gap > maxGap) {
            maxGap = gap;
            gapStart = i;
        }
    }

    // Only worth wrapping when an interior gap is wider than the gap that the
    // naive [min, max] range already leaves open across the antimeridian.
    const antimeridianGap = 360 - naiveSpan;
    if (maxGap <= antimeridianGap) return null;

    return [sorted[gapStart + 1], sorted[gapStart] + ANTIMERIDIAN_LON_SHIFT];
}

/**
 * Return an unwrapped version of a `[lon0, lon1]` longitude range.