Function intervalScaleCalcNiceTicks

src/coord/axisNiceTicks.ts:118–150

(
    scale: IntervalScale,
    opt: Pick<ScaleCalcNiceMethodOpt, 'splitNumber' | 'minInterval' | 'maxInterval' | 'userInterval'>
)

// ------ START: IntervalScale Nice ------

function intervalScaleCalcNiceTicks(
    scale: IntervalScale,
    opt: Pick<ScaleCalcNiceMethodOpt, 'splitNumber' | 'minInterval' | 'maxInterval' | 'userInterval'>
): IntervalScaleConfig {
    const splitNumber = ensureValidSplitNumber(opt.splitNumber, 5);
    // Use the span in the innermost linear space to calculate nice ticks.
    const span = getScaleLinearSpanEffective(scale);

    if (__DEV__) {
        assert(isFinite(span) && span > 0); // It should have been ensured by `intervalScaleEnsureValidExtent`.
    }

    const minInterval = opt.minInterval;
    const maxInterval = opt.maxInterval;

    let interval = nice(span / splitNumber, true);
    if (minInterval != null && interval < minInterval) {
        interval = minInterval;
    }
    if (maxInterval != null && interval > maxInterval) {
        interval = maxInterval;
    }

    const intervalPrecision = getIntervalPrecision(interval);
    const extent = scale.getExtent();
    // By design, the `niceExtent` is inside the original extent
    const niceExtent = [
        round(mathCeil(extent[0] / interval) * interval, intervalPrecision),
        round(mathFloor(extent[1] / interval) * interval, intervalPrecision)
    ];

    return {interval, intervalPrecision, niceExtent};
};

// ------ END: IntervalScale Nice ------