Function createEventManager

src/interaction/createEventManager.ts:40–213

(canvas: HTMLCanvasElement, initialGridArea: GridArea)

const DEFAULT_TAP_MAX_TIME_MS = 500;

export function createEventManager(canvas: HTMLCanvasElement, initialGridArea: GridArea): EventManager {
  let disposed = false;
  let gridArea = initialGridArea;

  const listeners: ListenerRegistry = {
    mousemove: new Set<ChartGPUEventCallback>(),
    click: new Set<ChartGPUEventCallback>(),
    mouseleave: new Set<ChartGPUEventCallback>(),
  };

  let tapCandidate: TapCandidate | null = null;
  let suppressNextLostPointerCaptureId: number | null = null;

  const toPayload = (e: PointerEvent): ChartGPUEventPayload | null => {
    const rect = canvas.getBoundingClientRect();
    if (rect.width === 0 || rect.height === 0) return null;

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

    const plotLeftCss = gridArea.left;
    const plotTopCss = gridArea.top;
    const plotWidthCss = rect.width - gridArea.left - gridArea.right;
    const plotHeightCss = rect.height - gridArea.top - gridArea.bottom;

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

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

    return { x, y, gridX, gridY, plotWidthCss, plotHeightCss, isInGrid, originalEvent: e };
  };

  const emit = (eventName: ChartGPUEventName, e: PointerEvent): void => {
    const payload = toPayload(e);
    if (!payload) return;

    for (const cb of listeners[eventName]) cb(payload);
  };

  const clearTapCandidateIfMatches = (e: PointerEvent): void => {
    if (!tapCandidate) return;
    if (!e.isPrimary) return;
    if (e.pointerId !== tapCandidate.pointerId) return;
    tapCandidate = null;
  };

  const onPointerMove = (e: PointerEvent): void => {
    if (disposed) return;
    emit('mousemove', e);
  };

  const onPointerLeave = (e: PointerEvent): void => {
    if (disposed) return;