sentry/static/app/views/performance/newTraceDetails/traceRenderers/virtualizedViewManager.tsx

import {mat3, vec2} from 'gl-matrix';

import {getDuration} from 'sentry/utils/formatters';
import clamp from 'sentry/utils/number/clamp';
import {requestAnimationTimeout} from 'sentry/utils/profiling/hooks/useVirtualizedTree/virtualizedTreeUtils';
import type {
  TraceTree,
  TraceTreeNode,
} from 'sentry/views/performance/newTraceDetails/traceModels/traceTree';
import {TraceRowWidthMeasurer} from 'sentry/views/performance/newTraceDetails/traceRenderers/traceRowWidthMeasurer';
import {TraceTextMeasurer} from 'sentry/views/performance/newTraceDetails/traceRenderers/traceTextMeasurer';
import {TraceView} from 'sentry/views/performance/newTraceDetails/traceRenderers/traceView';

const DIVIDER_WIDTH = 6;

function easeOutSine(x: number): number {
  return Math.sin((x * Math.PI) / 2);
}

type ViewColumn = {
  column_nodes: TraceTreeNode<TraceTree.NodeValue>[];
  column_refs: (HTMLElement | undefined)[];
  translate: [number, number];
  width: number;
};

type ArgumentTypes<F> = F extends (...args: infer A) => any ? A : never;
type EventStore = {
  [K in keyof VirtualizedViewManagerEvents]: Set<VirtualizedViewManagerEvents[K]>;
};
interface VirtualizedViewManagerEvents {
  ['divider resize end']: (list_width: number) => void;
  ['virtualized list init']: () => void;
}

/**
 * Tracks the state of the virtualized view and manages the resizing of the columns.
 * Children components should call the appropriate register*Ref methods to register their
 * HTML elements.
 */

export type ViewManagerScrollAnchor = 'top' | 'center if outside' | 'center';

export class VirtualizedViewManager {
  // Represents the space of the entire trace, for example
  // a trace starting at 0 and ending at 1000 would have a space of [0, 1000]
  to_origin: number = 0;
  trace_space: TraceView = TraceView.Empty();
  // The view defines what the user is currently looking at, it is a subset
  // of the trace space. For example, if the user is currently looking at the
  // trace from 500 to 1000, the view would be represented by [x, width] = [500, 500]
  trace_view: TraceView = TraceView.Empty();
  // Represents the pixel space of the entire trace - this is the container
  // that we render to. For example, if the container is 1000px wide, the
  // pixel space would be [0, 1000]
  trace_physical_space: TraceView = TraceView.Empty();
  container_physical_space: TraceView = TraceView.Empty();

  events: EventStore = {
    ['divider resize end']: new Set<VirtualizedViewManagerEvents['divider resize end']>(),
    ['virtualized list init']: new Set<
      VirtualizedViewManagerEvents['virtualized list init']
    >(),
  };

  row_measurer: TraceRowWidthMeasurer<TraceTreeNode<TraceTree.NodeValue>> =
    new TraceRowWidthMeasurer();
  indicator_label_measurer: TraceRowWidthMeasurer<TraceTree['indicators'][0]> =
    new TraceRowWidthMeasurer();
  text_measurer: TraceTextMeasurer = new TraceTextMeasurer();

  resize_observer: ResizeObserver | null = null;
  list: VirtualizedList | null = null;

  scrolling_source: 'list' | 'fake scrollbar' | null = null;
  start_virtualized_index: number = 0;

  // HTML refs that we need to keep track of such
  // that rendering can be done programmatically
  divider: HTMLElement | null = null;
  container: HTMLElement | null = null;
  horizontal_scrollbar_container: HTMLElement | null = null;
  indicator_container: HTMLElement | null = null;

  intervals: (number | undefined)[] = [];
  // We want to render an indicator every 100px, but because we dont track resizing
  // of the container, we need to precompute the number of intervals we need to render.
  // We'll oversize the count by 3x, assuming no user will ever resize the window to 3x the
  // original size.
  interval_bars = new Array(Math.ceil(window.innerWidth / 100) * 3).fill(0);
  indicators: ({indicator: TraceTree['indicators'][0]; ref: HTMLElement} | undefined)[] =
    [];
  timeline_indicators: (HTMLElement | undefined)[] = [];
  span_bars: ({color: string; ref: HTMLElement; space: [number, number]} | undefined)[] =
    [];
  span_patterns: ({ref: HTMLElement; space: [number, number]} | undefined)[][] = [];
  invisible_bars: ({ref: HTMLElement; space: [number, number]} | undefined)[] = [];
  span_arrows: (
    | {
        position: 0 | 1;
        ref: HTMLElement;
        space: [number, number];
        visible: boolean;
      }
    | undefined
  )[] = [];
  span_text: ({ref: HTMLElement; space: [number, number]; text: string} | undefined)[] =
    [];

  // Holds the span to px matrix so we dont keep recalculating it
  span_to_px: mat3 = mat3.create();
  row_depth_padding: number = 22;

  // Smallest of time that can be displayed across the entire view.
  private readonly MAX_ZOOM_PRECISION = 1;
  private readonly ROW_PADDING_PX = 16;

  // Column configuration
  columns: Record<'list' | 'span_list', ViewColumn>;

  constructor(columns: {
    list: Pick<ViewColumn, 'width'>;
    span_list: Pick<ViewColumn, 'width'>;
  }) {
    this.columns = {
      list: {...columns.list, column_nodes: [], column_refs: [], translate: [0, 0]},
      span_list: {
        ...columns.span_list,
        column_nodes: [],
        column_refs: [],
        translate: [0, 0],
      },
    };

    this.registerContainerRef = this.registerContainerRef.bind(this);
    this.registerHorizontalScrollBarContainerRef =
      this.registerHorizontalScrollBarContainerRef.bind(this);
    this.registerDividerRef = this.registerDividerRef.bind(this);
    this.registerIndicatorContainerRef = this.registerIndicatorContainerRef.bind(this);

    this.onDividerMouseDown = this.onDividerMouseDown.bind(this);
    this.onDividerMouseUp = this.onDividerMouseUp.bind(this);
    this.onDividerMouseMove = this.onDividerMouseMove.bind(this);
    this.onSyncedScrollbarScroll = this.onSyncedScrollbarScroll.bind(this);
    this.onWheel = this.onWheel.bind(this);
    this.onWheelEnd = this.onWheelEnd.bind(this);
    this.onWheelStart = this.onWheelStart.bind(this);
    this.onNewMaxRowWidth = this.onNewMaxRowWidth.bind(this);
    this.onHorizontalScrollbarScroll = this.onHorizontalScrollbarScroll.bind(this);
  }

  once<K extends keyof VirtualizedViewManagerEvents>(eventName: K, cb: Function) {
    const wrapper = (...args: any[]) => {
      cb(...args);
      this.off(eventName, wrapper);
    };
    this.on(eventName, wrapper);
  }

  on<K extends keyof VirtualizedViewManagerEvents>(
    eventName: K,
    cb: VirtualizedViewManagerEvents[K]
  ): void {
    const set = this.events[eventName] as unknown as Set<VirtualizedViewManagerEvents[K]>;
    if (set.has(cb)) {
      return;
    }
    set.add(cb);
  }

  off<K extends keyof VirtualizedViewManagerEvents>(
    eventName: K,
    cb: VirtualizedViewManagerEvents[K]
  ): void {
    const set = this.events[eventName] as unknown as Set<VirtualizedViewManagerEvents[K]>;

    if (set.has(cb)) {
      set.delete(cb);
    }
  }

  dispatch<K extends keyof VirtualizedViewManagerEvents>(
    event: K,
    ...args: ArgumentTypes<VirtualizedViewManagerEvents[K]>
  ): void {
    for (const handler of this.events[event]) {
      // @ts-expect-error
      handler(...args);
    }
  }

  initializeTraceSpace(space: [x: number, y: number, width: number, height: number]) {
    this.to_origin = space[0];

    this.trace_space = new TraceView(0, 0, space[2], space[3]);
    this.trace_view = new TraceView(0, 0, space[2], space[3]);

    this.recomputeTimelineIntervals();
    this.recomputeSpanToPxMatrix();
  }

  initializePhysicalSpace(width: number, height: number) {
    this.container_physical_space = new TraceView(0, 0, width, height);
    this.trace_physical_space = new TraceView(
      0,
      0,
      width * this.columns.span_list.width,
      height
    );

    this.recomputeTimelineIntervals();
    this.recomputeSpanToPxMatrix();
  }

  dividerScale: 1 | undefined = undefined;
  dividerStartVec: [number, number] | null = null;
  previousDividerClientVec: [number, number] | null = null;

  onDividerMouseDown(event: MouseEvent) {
    if (!this.container) {
      return;
    }

    this.dividerScale = this.trace_view.width === this.trace_space.width ? 1 : undefined;
    this.dividerStartVec = [event.clientX, event.clientY];
    this.previousDividerClientVec = [event.clientX, event.clientY];

    document.body.style.cursor = 'ew-resize !important';
    document.body.style.userSelect = 'none';

    document.addEventListener('mouseup', this.onDividerMouseUp, {passive: true});
    document.addEventListener('mousemove', this.onDividerMouseMove, {
      passive: true,
    });
  }

  onDividerMouseUp(event: MouseEvent) {
    if (!this.container || !this.dividerStartVec) {
      return;
    }

    this.dividerScale = undefined;
    const distance = event.clientX - this.dividerStartVec[0];
    const distancePercentage = distance / this.container_physical_space.width;

    this.columns.list.width = this.columns.list.width + distancePercentage;
    this.columns.span_list.width = this.columns.span_list.width - distancePercentage;

    document.body.style.cursor = '';
    document.body.style.userSelect = '';

    this.dividerStartVec = null;
    this.previousDividerClientVec = null;

    this.enqueueOnScrollEndOutOfBoundsCheck();
    document.removeEventListener('mouseup', this.onDividerMouseUp);
    document.removeEventListener('mousemove', this.onDividerMouseMove);

    this.dispatch('divider resize end', this.columns.list.width);
  }

  onDividerMouseMove(event: MouseEvent) {
    if (!this.dividerStartVec || !this.divider || !this.previousDividerClientVec) {
      return;
    }

    const distance = event.clientX - this.dividerStartVec[0];
    const distancePercentage = distance / this.container_physical_space.width;

    this.trace_physical_space.width =
      (this.columns.span_list.width - distancePercentage) *
      this.container_physical_space.width;

    const physical_distance = this.previousDividerClientVec[0] - event.clientX;
    const config_distance_pct = physical_distance / this.trace_physical_space.width;
    const config_distance = this.trace_view.width * config_distance_pct;

    if (this.dividerScale) {
      // just recompute the draw matrix and let the view scale itself
      this.recomputeSpanToPxMatrix();
    } else {
      this.setTraceView({
        x: this.trace_view.x - config_distance,
        width: this.trace_view.width + config_distance,
      });
    }
    this.recomputeTimelineIntervals();
    this.draw({
      list: this.columns.list.width + distancePercentage,
      span_list: this.columns.span_list.width - distancePercentage,
    });

    this.previousDividerClientVec = [event.clientX, event.clientY];
  }

  private scrollbar_width: number = 0;
  onScrollbarWidthChange(width: number) {
    if (width === this.scrollbar_width) {
      return;
    }
    this.scrollbar_width = width;
    this.draw();
  }

  registerContainerRef(container: HTMLElement | null) {
    if (container) {
      this.initialize(container);
    } else {
      this.teardown();
    }
  }

  registerGhostRowRef(column: string, ref: HTMLElement | null) {
    if (column === 'list' && ref) {
      const scrollableElement = ref.children[0] as HTMLElement | undefined;
      if (scrollableElement) {
        ref.addEventListener('wheel', this.onSyncedScrollbarScroll, {passive: false});
      }
    }

    if (column === 'span_list' && ref) {
      ref.addEventListener('wheel', this.onWheel, {passive: false});
    }
  }

  registerList(list: VirtualizedList | null) {
    this.list = list;
  }

  registerIndicatorContainerRef(ref: HTMLElement | null) {
    if (ref) {
      const correction =
        (this.scrollbar_width / this.container_physical_space.width) *
        this.columns.span_list.width;
      ref.style.transform = `translateX(${-this.scrollbar_width}px)`;
      ref.style.width = (this.columns.span_list.width - correction) * 100 + '%';
    }
    this.indicator_container = ref;
  }

  registerDividerRef(ref: HTMLElement | null) {
    if (!ref) {
      if (this.divider) {
        this.divider.removeEventListener('mousedown', this.onDividerMouseDown);
      }
      this.divider = null;
      return;
    }

    this.divider = ref;
    this.divider.style.width = `${DIVIDER_WIDTH}px`;
    ref.addEventListener('mousedown', this.onDividerMouseDown, {passive: true});
  }

  registerSpanBarRef(
    ref: HTMLElement | null,
    space: [number, number],
    color: string,
    index: number
  ) {
    if (ref) {
      this.span_bars[index] = {ref, space, color};
    }

    if (ref) {
      this.drawSpanBar(this.span_bars[index]!);
      this.span_bars[index]!.ref.style.backgroundColor = color;
    }
  }

  registerArrowRef(ref: HTMLElement | null, space: [number, number], index: number) {
    if (ref) {
      this.span_arrows[index] = {ref, space, visible: false, position: 0};
    }
  }

  registerSpanBarTextRef(
    ref: HTMLElement | null,
    text: string,
    space: [number, number],
    index: number
  ) {
    if (ref) {
      this.span_text[index] = {ref, text, space};
      this.drawSpanText(this.span_text[index]!, this.columns.list.column_nodes[index]);
    }
  }

  registerInvisibleBarRef(
    ref: HTMLElement | null,
    space: [number, number],
    index: number
  ) {
    if (ref) {
      this.invisible_bars[index] = ref ? {ref, space} : undefined;

      const span_transform = this.computeSpanCSSMatrixTransform(space);
      ref.style.transform = `matrix(${span_transform.join(',')}`;
      const inverseScale = Math.round((1 / span_transform[0]) * 1e4) / 1e4;
      ref.style.setProperty(
        '--inverse-span-scale',
        // @ts-expect-error this is a number
        isNaN(inverseScale) ? 1 : inverseScale
      );
    }
  }

  registerColumnRef(
    column: string,
    ref: HTMLElement | null,
    index: number,
    node: TraceTreeNode<any>
  ) {
    if (column === 'list' && ref) {
      const scrollableElement = ref.children[0] as HTMLElement | undefined;

      if (scrollableElement) {
        scrollableElement.style.transform = `translateX(${this.columns.list.translate[0]}px)`;
        this.row_measurer.enqueueMeasure(node, scrollableElement as HTMLElement);
        ref.addEventListener('wheel', this.onSyncedScrollbarScroll, {passive: false});
      }
    }

    if (column === 'span_list' && ref) {
      ref.addEventListener('wheel', this.onWheel, {passive: false});
    }

    if (ref && node) {
      this.columns[column].column_refs[index] = ref;
      this.columns[column].column_nodes[index] = node;
    }
  }

  registerIndicatorRef(
    ref: HTMLElement | null,
    index: number,
    indicator: TraceTree['indicators'][0]
  ) {
    if (!ref) {
      const element = this.indicators[index]?.ref;
      if (element) {
        element.removeEventListener('wheel', this.onWheel);
      }
    } else {
      this.indicators[index] = {ref, indicator};
    }

    if (ref) {
      const label = ref.children[0] as HTMLElement | undefined;
      if (label) {
        this.indicator_label_measurer.enqueueMeasure(indicator, label);
      }

      ref.addEventListener('wheel', this.onWheel, {passive: false});
      ref.style.transform = `translateX(${this.computeTransformXFromTimestamp(
        indicator.start
      )}px)`;
    }
  }

  registerTimelineIndicatorRef(ref: HTMLElement | null, index: number) {
    if (ref) {
      this.timeline_indicators[index] = ref;
      this.drawTimelineInterval(ref, index);
    }
  }

  getConfigSpaceCursor(cursor: {x: number; y: number}): [number, number] {
    const left_percentage = cursor.x / this.trace_physical_space.width;
    const left_view = left_percentage * this.trace_view.width;

    return [this.trace_view.x + left_view, 0];
  }

  onWheel(event: WheelEvent) {
    if (event.metaKey || event.ctrlKey) {
      event.preventDefault();
      if (!this.onWheelEndRaf) {
        this.onWheelStart();
      }
      this.enqueueOnWheelEndRaf();

      const scale = 1 - event.deltaY * 0.01 * -1;
      const configSpaceCursor = this.getConfigSpaceCursor({
        x: event.offsetX,
        y: event.offsetY,
      });

      const center = vec2.fromValues(configSpaceCursor[0], 0);
      const centerScaleMatrix = mat3.create();

      mat3.fromTranslation(centerScaleMatrix, center);
      mat3.scale(centerScaleMatrix, centerScaleMatrix, vec2.fromValues(scale, 1));
      mat3.translate(
        centerScaleMatrix,
        centerScaleMatrix,
        vec2.fromValues(-center[0], 0)
      );

      const newView = this.trace_view.transform(centerScaleMatrix);
      this.setTraceView({
        x: newView[0],
        width: newView[2],
      });
      this.draw();
    } else {
      if (!this.onWheelEndRaf) {
        this.onWheelStart();
      }
      this.enqueueOnWheelEndRaf();

      // Holding shift key allows for horizontal scrolling
      const distance = event.shiftKey ? event.deltaY : event.deltaX;
      if (
        event.shiftKey ||
        (!event.shiftKey && Math.abs(event.deltaX) > Math.abs(event.deltaY))
      ) {
        event.preventDefault();
      }

      const physical_delta_pct = distance / this.trace_physical_space.width;
      const view_delta = physical_delta_pct * this.trace_view.width;

      this.setTraceView({
        x: this.trace_view.x + view_delta,
      });
      this.draw();
    }
  }

  onBringRowIntoView(space: [number, number]) {
    if (this.zoomIntoSpaceRaf !== null) {
      window.cancelAnimationFrame(this.zoomIntoSpaceRaf);
      this.zoomIntoSpaceRaf = null;
    }

    if (space[0] - this.to_origin > this.trace_view.x) {
      this.onZoomIntoSpace([
        space[0] + space[1] / 2 - this.trace_view.width / 2,
        this.trace_view.width,
      ]);
    } else if (space[0] - this.to_origin < this.trace_view.x) {
      this.onZoomIntoSpace([
        space[0] + space[1] / 2 - this.trace_view.width / 2,
        this.trace_view.width,
      ]);
    }
  }

  animateViewTo(node_space: [number, number]) {
    const start = node_space[0];
    const width = node_space[1] > 0 ? node_space[1] : this.trace_view.width;
    const margin = 0.2 * width;

    this.setTraceView({x: start - margin - this.to_origin, width: width + margin * 2});
    this.draw();
  }

  zoomIntoSpaceRaf: number | null = null;
  onZoomIntoSpace(space: [number, number]) {
    let distance_x = space[0] - this.to_origin - this.trace_view.x;
    let final_x = space[0] - this.to_origin;
    let final_width = space[1];
    const distance_width = this.trace_view.width - space[1];

    if (space[1] < this.MAX_ZOOM_PRECISION) {
      distance_x -= this.MAX_ZOOM_PRECISION / 2 - space[1] / 2;
      final_x -= this.MAX_ZOOM_PRECISION / 2 - space[1] / 2;
      final_width = this.MAX_ZOOM_PRECISION;
    }

    const start_x = this.trace_view.x;
    const start_width = this.trace_view.width;

    const max_distance = Math.max(Math.abs(distance_x), Math.abs(distance_width));
    const p = max_distance !== 0 ? Math.log10(max_distance) : 1;
    // We need to clamp the duration to prevent the animation from being too slow,
    // sometimes the distances are very large as traces can be hours in duration
    const duration = clamp(200 + 70 * Math.abs(p), 200, 600);

    const start = performance.now();
    const rafCallback = (now: number) => {
      const elapsed = now - start;
      const progress = elapsed / duration;

      const eased = easeOutSine(progress);

      const x = start_x + distance_x * eased;
      const width = start_width - distance_width * eased;

      this.setTraceView({x, width});
      this.draw();

      if (progress < 1) {
        this.zoomIntoSpaceRaf = window.requestAnimationFrame(rafCallback);
      } else {
        this.zoomIntoSpaceRaf = null;
        this.setTraceView({x: final_x, width: final_width});
        this.draw();
      }
    };

    this.zoomIntoSpaceRaf = window.requestAnimationFrame(rafCallback);
  }

  resetZoom() {
    this.onZoomIntoSpace([this.to_origin, this.trace_space.width]);
  }

  onWheelEndRaf: number | null = null;
  enqueueOnWheelEndRaf() {
    if (this.onWheelEndRaf !== null) {
      window.cancelAnimationFrame(this.onWheelEndRaf);
    }

    const start = performance.now();
    const rafCallback = (now: number) => {
      const elapsed = now - start;
      if (elapsed > 200) {
        this.onWheelEnd();
      } else {
        this.onWheelEndRaf = window.requestAnimationFrame(rafCallback);
      }
    };

    this.onWheelEndRaf = window.requestAnimationFrame(rafCallback);
  }

  onWheelStart() {
    for (let i = 0; i < this.columns.span_list.column_refs.length; i++) {
      const span_list = this.columns.span_list.column_refs[i];
      if (span_list?.children?.[0]) {
        (span_list.children[0] as HTMLElement).style.pointerEvents = 'none';
      }
      const span_text = this.span_text[i];
      if (span_text) {
        span_text.ref.style.pointerEvents = 'none';
      }
    }

    for (let i = 0; i < this.indicators.length; i++) {
      const indicator = this.indicators[i];
      if (indicator?.ref) {
        indicator.ref.style.pointerEvents = 'none';
      }
    }
  }

  onWheelEnd() {
    this.onWheelEndRaf = null;

    for (let i = 0; i < this.columns.span_list.column_refs.length; i++) {
      const span_list = this.columns.span_list.column_refs[i];
      if (span_list?.children?.[0]) {
        (span_list.children[0] as HTMLElement).style.pointerEvents = 'auto';
      }
      const span_text = this.span_text[i];
      if (span_text) {
        span_text.ref.style.pointerEvents = 'auto';
      }
    }
    for (let i = 0; i < this.indicators.length; i++) {
      const indicator = this.indicators[i];
      if (indicator?.ref) {
        indicator.ref.style.pointerEvents = 'auto';
      }
    }
  }

  setTraceView(view: {width?: number; x?: number}) {
    // In cases where a trace might have a single error, there is no concept of a timeline
    if (this.trace_view.width === 0) {
      return;
    }
    const x = view.x ?? this.trace_view.x;
    const width = view.width ?? this.trace_view.width;

    this.trace_view.x = clamp(x, 0, this.trace_space.width - width);
    this.trace_view.width = clamp(
      width,
      this.MAX_ZOOM_PRECISION,
      this.trace_space.width - this.trace_view.x
    );

    this.recomputeTimelineIntervals();
    this.recomputeSpanToPxMatrix();
  }

  registerHorizontalScrollBarContainerRef(ref: HTMLElement | null) {
    if (ref) {
      ref.style.width = Math.round(this.columns.list.width * 100) + '%';
      ref.addEventListener('scroll', this.onHorizontalScrollbarScroll, {passive: false});
    } else {
      if (this.horizontal_scrollbar_container) {
        this.horizontal_scrollbar_container.removeEventListener(
          'scroll',
          this.onHorizontalScrollbarScroll
        );
      }
    }

    this.horizontal_scrollbar_container = ref;
  }

  onNewMaxRowWidth(max) {
    this.syncHorizontalScrollbar(max);
  }

  syncHorizontalScrollbar(max: number) {
    const child = this.horizontal_scrollbar_container?.children[0] as
      | HTMLElement
      | undefined;

    if (child) {
      child.style.width =
        Math.round(max - this.scrollbar_width + this.ROW_PADDING_PX) + 'px';
    }
  }

  onHorizontalScrollbarScroll(_event: Event) {
    if (!this.scrolling_source) {
      this.scrolling_source = 'fake scrollbar';
    }

    if (this.scrolling_source !== 'fake scrollbar') {
      return;
    }

    const scrollLeft = this.horizontal_scrollbar_container?.scrollLeft;
    if (typeof scrollLeft !== 'number') {
      return;
    }

    this.enqueueOnScrollEndOutOfBoundsCheck();
    this.columns.list.translate[0] = this.clampRowTransform(-scrollLeft);

    const rows = Array.from(
      document.querySelectorAll('.TraceRow .TraceLeftColumn > div')
    ) as HTMLElement[];

    for (const row of rows) {
      row.style.transform = `translateX(${this.columns.list.translate[0]}px)`;
    }
  }

  syncedRaf: number | null = null;
  onSyncedScrollbarScroll(event: WheelEvent) {
    if (!this.scrolling_source) {
      this.scrolling_source = 'list';
    }

    if (this.scrolling_source !== 'list') {
      return;
    }

    // Holding shift key allows for horizontal scrolling
    const distance = event.shiftKey ? event.deltaY : event.deltaX;

    if (Math.abs(event.deltaX) !== 0) {
      // Prevents firing back/forward navigation
      event.preventDefault();
    } else {
      return;
    }

    if (this.bringRowIntoViewAnimation !== null) {
      window.cancelAnimationFrame(this.bringRowIntoViewAnimation);
      this.bringRowIntoViewAnimation = null;
    }

    this.enqueueOnScrollEndOutOfBoundsCheck();

    const newTransform = this.clampRowTransform(
      this.columns.list.translate[0] - distance
    );

    if (newTransform === this.columns.list.translate[0]) {
      return;
    }

    this.columns.list.translate[0] = newTransform;

    const rows = Array.from(
      document.querySelectorAll('.TraceRow .TraceLeftColumn > div')
    ) as HTMLElement[];

    for (const row of rows) {
      row.style.transform = `translateX(${this.columns.list.translate[0]}px)`;
    }
    this.horizontal_scrollbar_container!.scrollLeft = -Math.round(
      this.columns.list.translate[0]
    );
  }

  clampRowTransform(transform: number): number {
    const columnWidth = this.columns.list.width * this.container_physical_space.width;
    const max = this.row_measurer.max - columnWidth + this.ROW_PADDING_PX;

    if (this.row_measurer.queue.length > 0) {
      this.row_measurer.drain();
    }

    if (this.row_measurer.max < columnWidth) {
      return 0;
    }

    // Sometimes the wheel event glitches or jumps to a very high value
    if (transform > 0) {
      return 0;
    }
    if (transform < -max) {
      return -max;
    }

    return transform;
  }

  scrollEndSyncRaf: {id: number} | null = null;
  enqueueOnScrollEndOutOfBoundsCheck() {
    if (this.bringRowIntoViewAnimation !== null) {
      // Dont enqueue updates while view is scrolling
      return;
    }

    window.cancelAnimationFrame(this.scrollEndSyncRaf?.id ?? 0);

    this.scrollEndSyncRaf = requestAnimationTimeout(() => {
      this.onScrollEndOutOfBoundsCheck();
    }, 300);
  }

  onScrollEndOutOfBoundsCheck() {
    this.scrollEndSyncRaf = null;
    this.scrolling_source = null;

    const translation = this.columns.list.translate[0];
    let min = Number.POSITIVE_INFINITY;
    let max = Number.NEGATIVE_INFINITY;
    let innerMostNode: TraceTreeNode<any> | undefined;

    for (let i = 5; i < this.columns.span_list.column_refs.length - 5; i++) {
      const width = this.row_measurer.cache.get(this.columns.list.column_nodes[i]);
      if (width === undefined) {
        // this is unlikely to happen, but we should trigger a sync measure event if it does
        continue;
      }

      min = Math.min(min, width);
      max = Math.max(max, width);
      innerMostNode =
        !innerMostNode || this.columns.list.column_nodes[i].depth < innerMostNode.depth
          ? this.columns.list.column_nodes[i]
          : innerMostNode;
    }

    if (innerMostNode) {
      if (translation + max < 0) {
        this.scrollRowIntoViewHorizontally(innerMostNode);
      } else if (
        translation + innerMostNode.depth * this.row_depth_padding >
        this.columns.list.width * this.container_physical_space.width
      ) {
        this.scrollRowIntoViewHorizontally(innerMostNode);
      }
    }
  }

  isOutsideOfViewOnKeyDown(node: TraceTreeNode<any>): boolean {
    const width = this.row_measurer.cache.get(node);
    if (width === undefined) {
      // this is unlikely to happen, but we should trigger a sync measure event if it does
      return false;
    }

    const translation = this.columns.list.translate[0];

    return (
      translation + node.depth * this.row_depth_padding < 0 ||
      translation + node.depth * this.row_depth_padding >
        (this.columns.list.width * this.container_physical_space.width) / 2
    );
  }

  scrollRowIntoViewHorizontally(
    node: TraceTreeNode<any>,
    duration: number = 600,
    offset_px: number = 0,
    position: 'exact' | 'measured' = 'measured'
  ) {
    const depth_px = -node.depth * this.row_depth_padding + offset_px;
    const newTransform =
      position === 'exact' ? depth_px : this.clampRowTransform(depth_px);

    this.animateScrollColumnTo(newTransform, duration);
  }

  bringRowIntoViewAnimation: number | null = null;
  animateScrollColumnTo(x: number, duration: number) {
    const start = performance.now();

    const startPosition = this.columns.list.translate[0];
    const distance = x - startPosition;

    if (duration === 0) {
      const rows = Array.from(
        document.querySelectorAll('.TraceRow .TraceLeftColumn > div')
      ) as HTMLElement[];

      for (const row of rows) {
        row.style.transform = `translateX(${this.columns.list.translate[0]}px)`;
      }

      this.columns.list.translate[0] = x;
      if (this.horizontal_scrollbar_container) {
        this.horizontal_scrollbar_container.scrollLeft = -x;
      }
      dispatchJestScrollUpdate(this.horizontal_scrollbar_container!);
      return;
    }

    const animate = (now: number) => {
      const elapsed = now - start;
      const progress = duration > 0 ? elapsed / duration : 1;
      const eased = easeOutSine(progress);

      const pos = startPosition + distance * eased;

      const rows = Array.from(
        document.querySelectorAll('.TraceRow .TraceLeftColumn > div')
      ) as HTMLElement[];

      for (const row of rows) {
        row.style.transform = `translateX(${this.columns.list.translate[0]}px)`;
      }

      if (progress < 1) {
        this.columns.list.translate[0] = pos;
        this.bringRowIntoViewAnimation = window.requestAnimationFrame(animate);
      } else {
        this.bringRowIntoViewAnimation = null;
        this.horizontal_scrollbar_container!.scrollLeft = -x;
        this.columns.list.translate[0] = x;
      }

      dispatchJestScrollUpdate(this.horizontal_scrollbar_container!);
    };

    this.bringRowIntoViewAnimation = window.requestAnimationFrame(animate);
  }

  initialize(container: HTMLElement) {
    if (this.container !== container && this.resize_observer !== null) {
      this.teardown();
      return;
    }

    this.container = container;
    this.drawContainers(this.container, {
      list_width: this.columns.list.width,
      span_list_width: this.columns.span_list.width,
    });

    this.row_measurer.on('max', this.onNewMaxRowWidth);
    this.resize_observer = new ResizeObserver(entries => {
      const entry = entries[0];
      if (!entry) {
        throw new Error('ResizeObserver entry is undefined');
      }

      this.initializePhysicalSpace(entry.contentRect.width, entry.contentRect.height);
      this.draw();
    });

    this.resize_observer.observe(container);
  }

  recomputeSpanToPxMatrix() {
    const traceViewToSpace = this.trace_space.between(this.trace_view);
    const tracePhysicalToView = this.trace_physical_space.between(this.trace_space);

    this.span_to_px = mat3.multiply(
      this.span_to_px,
      traceViewToSpace,
      tracePhysicalToView
    );
  }

  computeRelativeLeftPositionFromOrigin(
    timestamp: number,
    entire_space: [number, number]
  ) {
    return (timestamp - entire_space[0]) / entire_space[1];
  }

  recomputeTimelineIntervals() {
    if (this.trace_view.width === 0) {
      this.intervals[0] = 0;
      this.intervals[1] = 0;
      for (let i = 2; i < this.intervals.length; i++) {
        this.intervals[i] = undefined;
      }
      return;
    }
    const tracePhysicalToView = this.trace_physical_space.between(this.trace_view);
    const time_at_100 =
      tracePhysicalToView[0] * (100 * window.devicePixelRatio) +
      tracePhysicalToView[6] -
      this.trace_view.x;

    computeTimelineIntervals(this.trace_view, time_at_100, this.intervals);
  }

  readonly span_matrix: [number, number, number, number, number, number] = [
    1, 0, 0, 1, 0, 0,
  ];

  computeSpanCSSMatrixTransform(
    space: [number, number]
  ): [number, number, number, number, number, number] {
    const scale = space[1] / this.trace_view.width;
    this.span_matrix[0] = Math.max(scale, this.span_to_px[0] / this.trace_view.width);
    this.span_matrix[4] =
      (space[0] - this.to_origin) / this.span_to_px[0] -
      this.trace_view.x / this.span_to_px[0];

    return this.span_matrix;
  }

  scrollToRow(index: number, anchor?: ViewManagerScrollAnchor) {
    if (!this.list) {
      return;
    }
    this.list.scrollToRow(index, anchor);
  }

  computeTransformXFromTimestamp(timestamp: number): number {
    return (timestamp - this.to_origin - this.trace_view.x) / this.span_to_px[0];
  }

  computeSpanTextPlacement(
    node: TraceTreeNode<TraceTree.NodeValue>,
    span_space: [number, number],
    text: string
  ): [number, number] {
    const text_left = span_space[0] > this.to_origin + this.trace_space.width * 0.8;
    const width = this.text_measurer.measure(text);

    const has_profiles = node && node.profiles.length > 0;
    const has_error_icons =
      node &&
      (node.profiles.length > 0 ||
        node.errors.size > 0 ||
        node.performance_issues.size > 0);

    const has_icons = has_profiles || has_error_icons;

    const node_width = span_space[1] / this.span_to_px[0];
    const TEXT_PADDING = 2;
    // This is inaccurate in the case of left anchored text. In order to determine a true overlap, we would need to compute
    // the distance between the min timestamp of an icon and beginning of the span. Once we determine the distance, we can compute
    // the width and see if there is an actual overlap. Since this is a rare case which only happens in the case where we anchor the text
    // to the left (20% of the time) and the node may have many errors, this could be computationally expensive to do on every frame.
    // We'll live with the inaccuracy for now as it is purely visual and just make sure to handle a single error case as it will be easy
    // to determine if there is an overlap.
    const TEXT_PADDING_LEFT = text_left && has_icons ? 10 : TEXT_PADDING;

    const TEXT_PADDING_RIGHT =
      !text_left && has_icons
        ? node_width < 10
          ? // If the node is too small, we need to make sure the text is anchored to the right edge of the icon.
            // We take the distance from the right edge of the node to the right edge of the icon and subtract it from
            // the base width (10) and the base padding when (expanded) to get the correct padding. If we take only 10px
            // as our padding, the text can be anchored directly to the right edge of our icon - we want to preserve
            // a min padding of 2px.
            12 - node_width
          : TEXT_PADDING
        : TEXT_PADDING;

    // precompute all anchor points aot, so we make the control flow more readable.
    // this wastes some cycles, but it's not a big deal as computers go brrrr when it comes to simple arithmetic.
    /// |---| text
    const right_outside =
      this.computeTransformXFromTimestamp(span_space[0] + span_space[1]) +
      TEXT_PADDING_RIGHT;
    /// text |---|
    const left_outside =
      this.computeTransformXFromTimestamp(span_space[0]) - TEXT_PADDING_LEFT - width;

    // |   text|
    const right_inside =
      this.computeTransformXFromTimestamp(span_space[0] + span_space[1]) -
      width -
      TEXT_PADDING;
    // |text   |
    const left_inside = this.computeTransformXFromTimestamp(span_space[0]) + TEXT_PADDING;

    // Right edge of the window (when span extends beyond the view)
    const window_right =
      this.computeTransformXFromTimestamp(
        this.to_origin + this.trace_view.left + this.trace_view.width
      ) -
      width -
      TEXT_PADDING;
    const window_left =
      this.computeTransformXFromTimestamp(this.to_origin + this.trace_view.left) +
      TEXT_PADDING;

    const view_left = this.trace_view.x;
    const view_right = view_left + this.trace_view.width;

    const span_left = span_space[0] - this.to_origin;
    const span_right = span_left + span_space[1];

    const space_right = view_right - span_right;
    const space_left = span_left - view_left;

    // Span is completely outside of the view on the left side
    if (span_right < this.trace_view.x) {
      return text_left ? [1, right_inside] : [0, right_outside];
    }

    // Span is completely outside of the view on the right side
    if (span_left > this.trace_view.right) {
      return text_left ? [0, left_outside] : [1, left_inside];
    }

    // Span "spans" the entire view
    if (span_left <= this.trace_view.x && span_right >= this.trace_view.right) {
      return text_left ? [1, window_left] : [1, window_right];
    }

    const full_span_px_width = span_space[1] / this.span_to_px[0];

    if (text_left) {
      // While we have space on the left, place the text there
      if (space_left > 0) {
        return [0, left_outside];
      }

      const distance = span_right - this.trace_view.left;
      const visible_width = distance / this.span_to_px[0] - TEXT_PADDING;

      // If the text fits inside the visible portion of the span, anchor it to the left
      // side of the window so that it is visible while the user pans the view
      if (visible_width - TEXT_PADDING >= width) {
        return [1, window_left];
      }

      // If the text doesnt fit inside the visible portion of the span,
      // anchor it to the inside right place in the span.
      return [1, right_inside];
    }

    // While we have space on the right, place the text there
    if (space_right > 0) {
      if (
        // If the right edge of the span is within 10% to the right edge of the space,
        // try and fit the text inside the span if possible. In case the span is too short
        // to fit the text, text_left case above will take care of anchoring it to the left
        // of the view.

        // Note: the accurate way for us to determine if the text fits to the right side
        // of the view would have been to compute the scaling matrix for a non zoomed view at 0,0
        // origin and check if it fits into the distance of space right edge - span right edge. In practice
        // however, it seems that a magical number works just fine.
        span_right > this.trace_space.right * 0.9 &&
        space_right / this.span_to_px[0] < width
      ) {
        return [1, right_inside];
      }
      return [0, right_outside];
    }

    // If text fits inside the span
    if (full_span_px_width > width) {
      const distance = span_right - this.trace_view.right;
      const visible_width =
        (span_space[1] - distance) / this.span_to_px[0] - TEXT_PADDING;

      // If the text fits inside the visible portion of the span, anchor it to the right
      // side of the window so that it is visible while the user pans the view
      if (visible_width - TEXT_PADDING >= width) {
        return [1, window_right];
      }

      // If the text doesnt fit inside the visible portion of the span,
      // anchor it to the inside left of the span
      return [1, left_inside];
    }

    return [0, right_outside];
  }

  last_indicator_width = 0;
  draw(options: {list?: number; span_list?: number} = {}) {
    const list_width = options.list ?? this.columns.list.width;
    const span_list_width = options.span_list ?? this.columns.span_list.width;

    this.drawContainers(this.container, {
      list_width,
      span_list_width,
    });

    for (let i = 0; i < this.columns.list.column_refs.length; i++) {
      this.drawSpanBar(this.span_bars[i]);
      this.drawSpanText(this.span_text[i], this.columns.list.column_nodes[i]);
      this.drawSpanArrow(this.span_bars[i], this.span_arrows[i]);
    }

    this.drawInvisibleBars();

    let start_indicator = 0;
    let end_indicator = this.indicators.length;

    while (start_indicator < this.indicators.length - 1) {
      const indicator = this.indicators[start_indicator];
      if (!indicator?.indicator) {
        start_indicator++;
        continue;
      }

      if (indicator.indicator.start < this.to_origin + this.trace_view.left) {
        start_indicator++;
        continue;
      }

      break;
    }

    while (end_indicator > start_indicator) {
      const last_indicator = this.indicators[end_indicator - 1];
      if (!last_indicator) {
        end_indicator--;
        continue;
      }
      if (last_indicator.indicator.start > this.to_origin + this.trace_view.right) {
        end_indicator--;
        continue;
      }
      break;
    }

    start_indicator = Math.max(0, start_indicator - 1);
    end_indicator = Math.min(this.indicators.length - 1, end_indicator);

    for (let i = 0; i < this.indicators.length; i++) {
      const entry = this.indicators[i];
      if (!entry) {
        continue;
      }

      if (i < start_indicator || i > end_indicator) {
        entry.ref.style.opacity = '0';
        continue;
      }

      const transform = this.computeTransformXFromTimestamp(entry.indicator.start);
      const label = entry.ref.children[0] as HTMLElement | undefined;

      const indicator_max = this.trace_physical_space.width + 1;
      const indicator_min = -1;

      const label_width = this.indicator_label_measurer.cache.get(entry.indicator);
      const clamped_transform = clamp(transform, -1, indicator_max);

      if (label_width === undefined) {
        entry.ref.style.transform = `translate(${clamp(transform, indicator_min, indicator_max)}px, 0)`;
        continue;
      }

      if (label) {
        const PADDING = 2;
        const label_window_left = PADDING;
        const label_window_right = -label_width - PADDING;

        if (transform < -1) {
          label.style.transform = `translateX(${label_window_left}px)`;
        } else if (transform >= indicator_max) {
          label.style.transform = `translateX(${label_window_right}px)`;
        } else {
          const space_left = transform - PADDING - label_width / 2;
          const space_right = transform + label_width / 2;

          if (space_left < 0) {
            const left = -label_width / 2 + Math.abs(space_left);
            label.style.transform = `translateX(${left - 1}px)`;
          } else if (space_right > this.trace_physical_space.width) {
            const right =
              -label_width / 2 - (space_right - this.trace_physical_space.width) - 1;
            label.style.transform = `translateX(${right}px)`;
          } else {
            label.style.transform = `translateX(${-label_width / 2}px)`;
          }
        }
      }

      entry.ref.style.opacity = '1';
      entry.ref.style.transform = `translate(${clamped_transform}px, 0)`;
    }

    this.drawTimelineIntervals();
  }

  // DRAW METHODS

  drawSpanBar(span_bar: this['span_bars'][0]) {
    if (!span_bar) return;

    const span_transform = this.computeSpanCSSMatrixTransform(span_bar?.space);
    span_bar.ref.style.transform = `matrix(${span_transform.join(',')}`;
    const inverseScale = Math.round((1 / span_transform[0]) * 1e4) / 1e4;
    span_bar.ref.style.setProperty(
      '--inverse-span-scale',
      // @ts-expect-error we set number value type on purpose
      isNaN(inverseScale) ? 1 : inverseScale
    );
  }

  drawSpanText(span_text: this['span_text'][0], node: TraceTreeNode<any> | undefined) {
    if (!span_text) return;

    const [inside, text_transform] = this.computeSpanTextPlacement(
      node!,
      span_text.space,
      span_text.text
    );

    if (text_transform === null) {
      return;
    }

    span_text.ref.style.color = inside ? 'white' : '';
    span_text.ref.style.transform = `translateX(${text_transform}px)`;
  }

  drawSpanArrow(span_bar: this['span_bars'][0], span_arrow: this['span_arrows'][0]) {
    if (!span_arrow || !span_bar) return;

    const outside_left =
      span_bar.space[0] - this.to_origin + span_bar.space[1] < this.trace_view.x;
    const outside_right = span_bar.space[0] - this.to_origin > this.trace_view.right;
    const visible = outside_left || outside_right;

    if (visible !== span_arrow.visible) {
      span_arrow.visible = visible;
      span_arrow.position = outside_left ? 0 : 1;

      if (visible) {
        span_arrow.ref.className = `TraceArrow Visible ${span_arrow.position === 0 ? 'Left' : 'Right'}`;
      } else {
        span_arrow.ref.className = 'TraceArrow';
      }
    }
  }

  drawTimelineInterval(ref: HTMLElement | undefined, index: number) {
    if (!ref) {
      return;
    }

    const interval = this.intervals[index];
    if (interval === undefined) {
      ref.style.opacity = '0';
      return;
    }

    const placement = this.computeTransformXFromTimestamp(this.to_origin + interval);

    ref.style.opacity = '1';
    ref.style.transform = `translateX(${placement}px)`;
    const label = ref.children[0] as HTMLElement | undefined;
    const duration = getDuration(interval / 1000, 2, true);

    if (label && label?.textContent !== duration) {
      label.textContent = duration;
    }
  }

  drawTimelineIntervals() {
    if (this.intervals[0] === 0 && this.intervals[1] === 0) {
      this.drawEmptyTimelineIntervals();

      for (let i = 2; i < this.timeline_indicators.length; i++) {
        const indicator = this.timeline_indicators[i];
        if (indicator) {
          indicator.style.opacity = '0';
        }
      }
      return;
    }
    for (let i = 0; i < this.timeline_indicators.length; i++) {
      this.drawTimelineInterval(this.timeline_indicators[i], i);
    }
  }

  // Special case for when the timeline is empty - we want to show the first and last
  // timeline indicators as 0ms instead of just a single 0ms indicator as it gives better
  // context to the user that start and end are both 0ms. If we were to draw a single 0ms
  // indicator, it leaves ambiguity for the user to think that the end might be missing
  drawEmptyTimelineIntervals() {
    const first = this.timeline_indicators[0];
    const last = this.timeline_indicators[1];

    if (first && last) {
      first.style.opacity = '1';
      last.style.opacity = '1';
      first.style.transform = `translateX(0)`;

      // 43 px offset is the width of a 0.00ms label, since we usually anchor the label to the right
      // side of the indicator, we need to offset it by the width of the label to make it look like
      // it is at the end of the timeline
      last.style.transform = `translateX(${this.trace_physical_space.width - 43}px)`;
      const firstLabel = first.children[0] as HTMLElement | undefined;
      if (firstLabel) {
        firstLabel.textContent = '0.00ms';
      }
      const lastLabel = last.children[0] as HTMLElement | undefined;
      const lastLine = last.children[1] as HTMLElement | undefined;
      if (lastLine && lastLabel) {
        lastLabel.textContent = '0.00ms';
        lastLine.style.opacity = '0';
      }
    }
  }

  drawContainers(
    container: HTMLElement | null,
    options: {list_width: number; span_list_width: number}
  ) {
    if (!container) return;

    if (this.last_list_column_width !== options.list_width) {
      container.style.setProperty(
        '--list-column-width',
        // @ts-expect-error we set number value type on purpose
        Math.round(options.list_width * 1000) / 1000
      );
      this.last_list_column_width = options.list_width;
    }
    if (this.last_span_column_width !== options.span_list_width) {
      container.style.setProperty(
        '--span-column-width',
        // @ts-expect-error we set number value type on purpose
        Math.round(options.span_list_width * 1000) / 1000
      );
      this.last_span_column_width = options.span_list_width;
    }

    if (this.indicator_container) {
      const correction =
        (this.scrollbar_width / this.container_physical_space.width) *
        options.span_list_width;
      this.indicator_container.style.transform = `transform(${-this.scrollbar_width}px, 0)`;
      const new_indicator_container_width = options.span_list_width - correction;
      if (this.last_indicator_width !== new_indicator_container_width) {
        this.indicator_container.style.width = new_indicator_container_width * 100 + '%';
        this.last_indicator_width = new_indicator_container_width;
      }
    }

    if (this.divider) {
      this.divider.style.transform = `translate(
        ${
          Math.round(
            (options.list_width *
              (this.container_physical_space.width - this.scrollbar_width) -
              DIVIDER_WIDTH / 2 -
              1) *
              10
          ) / 10
        }px, 0)`;
    }
  }
  last_list_column_width = 0;
  last_span_column_width = 0;

  drawInvisibleBars() {
    for (let i = 0; i < this.invisible_bars.length; i++) {
      const invisible_bar = this.invisible_bars[i];
      if (invisible_bar) {
        const span_transform = this.computeSpanCSSMatrixTransform(invisible_bar?.space);
        invisible_bar.ref.style.transform = `matrix(${span_transform.join(',')}`;
        const inverseScale = Math.round((1 / span_transform[0]) * 1e4) / 1e4;
        invisible_bar.ref.style.setProperty(
          '--inverse-span-scale',
          // @ts-expect-error we set number value type on purpose
          isNaN(inverseScale) ? 1 : inverseScale
        );
      }
    }
  }

  // END DRAW METHODS

  teardown() {
    this.row_measurer.off('max', this.onNewMaxRowWidth);

    if (this.resize_observer) {
      this.resize_observer.disconnect();
      this.resize_observer = null;
      this.container = null;
    }
  }
}

// Jest does not implement scroll updates, however since we have the
// middleware to handle scroll updates, we can dispatch a scroll event ourselves
function dispatchJestScrollUpdate(container: HTMLElement) {
  if (!container) return;
  if (process.env.NODE_ENV !== 'test') return;
  // since we do not tightly control how browsers handle event dispatching, dispatch it async
  window.requestAnimationFrame(() => {
    container.dispatchEvent(new CustomEvent('scroll'));
  });
}

function computeTimelineIntervals(
  view: TraceView,
  targetInterval: number,
  results: (number | undefined)[]
): void {
  const minInterval = Math.pow(10, Math.floor(Math.log10(targetInterval)));
  let interval = minInterval;

  if (targetInterval / interval > 5) {
    interval *= 5;
  } else if (targetInterval / interval > 2) {
    interval *= 2;
  }

  let x = Math.ceil(view.x / interval) * interval;
  let idx = -1;
  if (x > 0) {
    x -= interval;
  }
  while (x <= view.right) {
    results[++idx] = x;
    x += interval;
  }

  while (idx < results.length - 1 && results[idx + 1] !== undefined) {
    results[++idx] = undefined;
  }
}

export class VirtualizedList {
  container: HTMLElement | null = null;

  scrollHeight: number = 0;
  scrollTop: number = 0;

  scrollToRow(index: number, anchor?: ViewManagerScrollAnchor) {
    if (!this.container) {
      return;
    }

    let position = index * 24;

    const top = this.container.scrollTop;
    const height = this.scrollHeight;

    if (anchor === 'top') {
      position = index * 24;
    } else if (anchor === 'center') {
      position = position - height / 2;
    } else if (anchor === 'center if outside') {
      if (position < top) {
        // Element is above the view
        position = position - height / 2;
      } else if (position > top + height) {
        // Element below the view
        position = position - height / 2;
      } else {
        // Element is inside the view
        return;
      }
    } else {
      // If no anchor is provided, we default to 'auto'
      if (position < top) {
        position = position;
      } else if (position > top + height) {
        position = index * 24 - height + 24;
      } else {
        return;
      }
    }

    this.container.scrollTop = position;
    dispatchJestScrollUpdate(this.container);
  }
}