react-resizable-panels/src/utils/calculateAriaValues.ts

React components for resizable panel groups/layouts

import { PanelData } from "../Panel";
import { assert } from "./assert";

export function calculateAriaValues({
  layout,
  panelsArray,
  pivotIndices,
}: {
  layout: number[];
  panelsArray: PanelData[];
  pivotIndices: number[];
}) {
  let currentMinSize = 0;
  let currentMaxSize = 100;
  let totalMinSize = 0;
  let totalMaxSize = 0;

  const firstIndex = pivotIndices[0];
  assert(firstIndex != null, "No pivot index found");

  // A panel's effective min/max sizes also need to account for other panel's sizes.
  panelsArray.forEach((panelData, index) => {
    const { constraints } = panelData;
    const { maxSize = 100, minSize = 0 } = constraints;

    if (index === firstIndex) {
      currentMinSize = minSize;
      currentMaxSize = maxSize;
    } else {
      totalMinSize += minSize;
      totalMaxSize += maxSize;
    }
  });

  const valueMax = Math.min(currentMaxSize, 100 - totalMinSize);
  const valueMin = Math.max(currentMinSize, 100 - totalMaxSize);

  const valueNow = layout[firstIndex];

  return {
    valueMax,
    valueMin,
    valueNow,
  };
}