Function getNearestPointFromPointerEvent

src/ChartGPU.ts:837–972

(
    e: PointerEvent
  )

  const resize = (): void => resizeInternal(true);

  const getNearestPointFromPointerEvent = (
    e: PointerEvent
  ): { readonly match: HitTestMatch | null; readonly isInGrid: boolean } => {
    const rect = canvas.getBoundingClientRect();
    if (!(rect.width > 0) || !(rect.height > 0)) return { match: null, isInGrid: false };

    const x = e.clientX - rect.left;
    const y = e.clientY - rect.top;

    const plotLeftCss = resolvedOptions.grid.left;
    const plotTopCss = resolvedOptions.grid.top;
    const plotWidthCss = rect.width - resolvedOptions.grid.left - resolvedOptions.grid.right;
    const plotHeightCss = rect.height - resolvedOptions.grid.top - resolvedOptions.grid.bottom;
    if (!(plotWidthCss > 0) || !(plotHeightCss > 0)) return { match: null, isInGrid: false };

    const gridX = x - plotLeftCss;
    const gridY = y - plotTopCss;

    const isInGrid =
      gridX >= 0 &&
      gridX <= plotWidthCss &&
      gridY >= 0 &&
      gridY <= plotHeightCss;

    if (!isInGrid) return { match: null, isInGrid: false };

    const xMin = resolvedOptions.xAxis.min ?? cachedGlobalBounds.xMin;
    const xMax = resolvedOptions.xAxis.max ?? cachedGlobalBounds.xMax;
    const yMin = resolvedOptions.yAxis.min ?? cachedGlobalBounds.yMin;
    const yMax = resolvedOptions.yAxis.max ?? cachedGlobalBounds.yMax;

    // Make hit-testing zoom-aware (mirror coordinator percent->domain mapping).
    const baseXDomain = normalizeDomain(xMin, xMax);
    const zoomRange = coordinator?.getZoomRange() ?? null;
    const xDomain = (() => {
      if (!zoomRange) return baseXDomain;
      const span = baseXDomain.max - baseXDomain.min;
      if (!Number.isFinite(span) || span === 0) return baseXDomain;
      const start = zoomRange.start;
      const end = zoomRange.end;
      const zMin = baseXDomain.min + (start / 100) * span;
      const zMax = baseXDomain.min + (end / 100) * span;
      return normalizeDomain(zMin, zMax);
    })();
    const yDomain = normalizeDomain(yMin, yMax);

    // Cache hit-testing scales for identical (rect, grid, axis domain) inputs.
    const canReuseScales =
      interactionScalesCache !== null &&
      interactionScalesCache.rectWidthCss === rect.width &&
      interactionScalesCache.rectHeightCss === rect.height &&
      interactionScalesCache.plotWidthCss === plotWidthCss &&
      interactionScalesCache.plotHeightCss === plotHeightCss &&
      interactionScalesCache.xDomainMin === xDomain.min &&
      interactionScalesCache.xDomainMax === xDomain.max &&
      interactionScalesCache.yDomainMin === yDomain.min &&
      interactionScalesCache.yDomainMax === yDomain.max;