Function computeAdaptiveTimeXAxisTicks

src/core/createRenderCoordinator.ts:1102–1187

(params: {
  readonly axisMin: number | null;
  readonly axisMax: number | null;
  readonly xScale: LinearScale;
  readonly plotClipLeft: number;
  readonly plotClipRight: number;
  readonly canvasCssWidth: number;
  readonly visibleRangeMs: number;
  readonly measureCtx: CanvasRenderingContext2D | null;
  readonly measureCache?: Map<string, number>;
  readonly fontSize: number;
  readonly fontFamily: string;
})

};

const computeAdaptiveTimeXAxisTicks = (params: {
  readonly axisMin: number | null;
  readonly axisMax: number | null;
  readonly xScale: LinearScale;
  readonly plotClipLeft: number;
  readonly plotClipRight: number;
  readonly canvasCssWidth: number;
  readonly visibleRangeMs: number;
  readonly measureCtx: CanvasRenderingContext2D | null;
  readonly measureCache?: Map<string, number>;
  readonly fontSize: number;
  readonly fontFamily: string;
}): { readonly tickCount: number; readonly tickValues: readonly number[] } => {
  const {
    axisMin,
    axisMax,
    xScale,
    plotClipLeft,
    plotClipRight,
    canvasCssWidth,
    visibleRangeMs,
    measureCtx,
    measureCache,
    fontSize,
    fontFamily,
  } = params;

  // Domain fallback matches `createAxisRenderer` (use explicit min/max when provided).
  const domainMin = finiteOrNull(axisMin) ?? xScale.invert(plotClipLeft);
  const domainMax = finiteOrNull(axisMax) ?? xScale.invert(plotClipRight);

  if (!measureCtx || canvasCssWidth <= 0) {
    return { tickCount: DEFAULT_TICK_COUNT, tickValues: generateLinearTicks(domainMin, domainMax, DEFAULT_TICK_COUNT) };
  }

  // Ensure the measurement font matches the overlay labels.
  measureCtx.font = `${fontSize}px ${fontFamily}`;
  if (measureCache && measureCache.size > 2000) measureCache.clear();

  // Pre-construct the font part of the cache key to avoid repeated concatenation.
  const cacheKeyPrefix = measureCache ? `${fontSize}px ${fontFamily}@@` : null;

  for (let tickCount = MAX_TIME_X_TICK_COUNT; tickCount >= MIN_TIME_X_TICK_COUNT; tickCount--) {
    const tickValues = generateLinearTicks(domainMin, domainMax, tickCount);

    // Compute label extents in *canvas-local CSS px* and ensure adjacent labels don't overlap.
    let prevRight = Number.NEGATIVE_INFINITY;
    let ok = true;

    for (let i = 0; i < tickValues.length; i++) {
      const v = tickValues[i]!;
      const label = formatTimeTickValue(v, visibleRangeMs);
      if (label == null) continue;

      const w = (() => {
        if (!cacheKeyPrefix) return measureCtx.measureText(label).width;
        const key = cacheKeyPrefix + label;
        const cached = measureCache!.get(key);