react-infinite-cursor/build/utils/infiniteHelpers.js

A browser-ready efficient scrolling container based on UITableView. Takes a cursor for rendering.

'use strict';

var ConstantInfiniteComputer = require('../computers/constantInfiniteComputer.js');
var ArrayInfiniteComputer = require('../computers/arrayInfiniteComputer.js');
var React = global.React || require('react');

function createInfiniteComputer(data, list) {
  var computer;
  var numberOfChildren = list.length;

  // This should be guaranteed by checkProps
  if (Array.isArray(data)) {
    computer = new ArrayInfiniteComputer(data, numberOfChildren);
  } else {
    computer = new ConstantInfiniteComputer(data, numberOfChildren);
  }
  return computer;
}

// Given the scrollTop of the container, computes the state the
// component should be in. The goal is to abstract all of this
// from any actual representation in the DOM.
// The window is the block with any preloadAdditionalHeight
// added to it.
function recomputeApertureStateFromOptionsAndScrollTop(_ref, scrollTop) {
  var preloadBatchSize = _ref.preloadBatchSize;
  var preloadAdditionalHeight = _ref.preloadAdditionalHeight;
  var infiniteComputer = _ref.infiniteComputer;
  return (function () {
    var blockNumber = preloadBatchSize === 0 ? 0 : Math.floor(scrollTop / preloadBatchSize),
        blockStart = preloadBatchSize * blockNumber,
        blockEnd = blockStart + preloadBatchSize,
        apertureTop = Math.max(0, blockStart - preloadAdditionalHeight),
        apertureBottom = Math.min(infiniteComputer.getTotalScrollableHeight(), blockEnd + preloadAdditionalHeight);

    return {
      displayIndexStart: infiniteComputer.getDisplayIndexStart(apertureTop),
      displayIndexEnd: infiniteComputer.getDisplayIndexEnd(apertureBottom)
    };
  })();
}

module.exports = {
  createInfiniteComputer: createInfiniteComputer,
  recomputeApertureStateFromOptionsAndScrollTop: recomputeApertureStateFromOptionsAndScrollTop
};