function stackViewer(stacks, nodes) {
  'use strict';

  // Constants used in rendering.
  const ROW = 20;
  const PADDING = 2;
  const MIN_WIDTH = 4;
  const MIN_TEXT_WIDTH = 16;
  const TEXT_MARGIN = 2;
  const FONT_SIZE = 12;
  const MIN_FONT_SIZE = 8;

  // Fields
  let pivots = [];          // Indices of currently selected data.Sources entries.
  let matches = new Set();  // Indices of sources that match search