@tamagui/react-native-web-lite/dist/esm/vendor/react-native/ViewabilityHelper/index.mjs

React Native for Web

import { invariant } from "@tamagui/react-native-web-internals";
class ViewabilityHelper {
  _config;
  _hasInteracted = false;
  _timers = /* @__PURE__ */new Set();
  _viewableIndices = [];
  _viewableItems = /* @__PURE__ */new Map();
  constructor(config = {
    viewAreaCoveragePercentThreshold: 0
  }) {
    this._config = config;
  }
  /**
   * Cleanup, e.g. on unmount. Clears any pending timers.
   */
  dispose() {
    this._timers.forEach(clearTimeout);
  }
  /**
   * Determines which items are viewable based on the current metrics and config.
   */
  computeViewableItems(props, scrollOffset, viewportHeight, getFrameMetrics, renderRange) {
    const itemCount = props.getItemCount(props.data);
    const {
      itemVisiblePercentThreshold,
      viewAreaCoveragePercentThreshold
    } = this._config;
    const viewAreaMode = viewAreaCoveragePercentThreshold != null;
    const viewablePercentThreshold = viewAreaMode ? viewAreaCoveragePercentThreshold : itemVisiblePercentThreshold;
    invariant(viewablePercentThreshold != null && itemVisiblePercentThreshold != null !== (viewAreaCoveragePercentThreshold != null), "Must set exactly one of itemVisiblePercentThreshold or viewAreaCoveragePercentThreshold");
    const viewableIndices = [];
    if (itemCount === 0) {
      return viewableIndices;
    }
    let firstVisible = -1;
    const {
      first,
      last
    } = renderRange || {
      first: 0,
      last: itemCount - 1
    };
    if (last >= itemCount) {
      console.warn("Invalid render range computing viewability " + JSON.stringify({
        renderRange,
        itemCount
      }));
      return [];
    }
    for (let idx = first; idx <= last; idx++) {
      const metrics = getFrameMetrics(idx, props);
      if (!metrics) {
        continue;
      }
      const top = metrics.offset - scrollOffset;
      const bottom = top + metrics.length;
      if (top < viewportHeight && bottom > 0) {
        firstVisible = idx;
        if (_isViewable(viewAreaMode, viewablePercentThreshold, top, bottom, viewportHeight, metrics.length)) {
          viewableIndices.push(idx);
        }
      } else if (firstVisible >= 0) {
        break;
      }
    }
    return viewableIndices;
  }
  /**
   * Figures out which items are viewable and how that has changed from before and calls
   * `onViewableItemsChanged` as appropriate.
   */
  onUpdate(props, scrollOffset, viewportHeight, getFrameMetrics, createViewToken, onViewableItemsChanged, renderRange) {
    const itemCount = props.getItemCount(props.data);
    if (this._config.waitForInteraction && !this._hasInteracted || itemCount === 0 || !getFrameMetrics(0, props)) {
      return;
    }
    let viewableIndices = [];
    if (itemCount) {
      viewableIndices = this.computeViewableItems(props, scrollOffset, viewportHeight, getFrameMetrics, renderRange);
    }
    if (this._viewableIndices.length === viewableIndices.length && this._viewableIndices.every((v, ii) => v === viewableIndices[ii])) {
      return;
    }
    this._viewableIndices = viewableIndices;
    if (this._config.minimumViewTime) {
      const handle = setTimeout(() => {
        this._timers.delete(handle);
        this._onUpdateSync(props, viewableIndices, onViewableItemsChanged, createViewToken);
      }, this._config.minimumViewTime);
      this._timers.add(handle);
    } else {
      this._onUpdateSync(props, viewableIndices, onViewableItemsChanged, createViewToken);
    }
  }
  /**
   * clean-up cached _viewableIndices to evaluate changed items on next update
   */
  resetViewableIndices() {
    this._viewableIndices = [];
  }
  /**
   * Records that an interaction has happened even if there has been no scroll.
   */
  recordInteraction() {
    this._hasInteracted = true;
  }
  _onUpdateSync(props, viewableIndicesToCheck, onViewableItemsChanged, createViewToken) {
    viewableIndicesToCheck = viewableIndicesToCheck.filter(ii => this._viewableIndices.includes(ii));
    const prevItems = this._viewableItems;
    const nextItems = new Map(viewableIndicesToCheck.map(ii => {
      const viewable = createViewToken(ii, true, props);
      return [viewable.key, viewable];
    }));
    const changed = [];
    for (const [key, viewable] of nextItems) {
      if (!prevItems.has(key)) {
        changed.push(viewable);
      }
    }
    for (const [key, viewable] of prevItems) {
      if (!nextItems.has(key)) {
        changed.push({
          ...viewable,
          isViewable: false
        });
      }
    }
    if (changed.length > 0) {
      this._viewableItems = nextItems;
      onViewableItemsChanged({
        viewableItems: Array.from(nextItems.values()),
        changed,
        viewabilityConfig: this._config
      });
    }
  }
}
function _isViewable(viewAreaMode, viewablePercentThreshold, top, bottom, viewportHeight, itemLength) {
  if (_isEntirelyVisible(top, bottom, viewportHeight)) {
    return true;
  } else {
    const pixels = _getPixelsVisible(top, bottom, viewportHeight);
    const percent = 100 * (viewAreaMode ? pixels / viewportHeight : pixels / itemLength);
    return percent >= viewablePercentThreshold;
  }
}
function _getPixelsVisible(top, bottom, viewportHeight) {
  const visibleHeight = Math.min(bottom, viewportHeight) - Math.max(top, 0);
  return Math.max(0, visibleHeight);
}
function _isEntirelyVisible(top, bottom, viewportHeight) {
  return top >= 0 && bottom <= viewportHeight && bottom > top;
}
var ViewabilityHelper_default = ViewabilityHelper;
export { ViewabilityHelper, ViewabilityHelper_default as default };
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