lighthouse/helpers/icons.js

> Stops you crashing into the rocks; lights the way

/**
 * @license
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
'use strict';

/**
 * @param {!Manifest=} manifest
 * @return {boolean} Does the manifest have any icons?
 */
function doExist(manifest) {
  if (!manifest || !manifest.icons) {
    return false;
  }
  if (!manifest.icons.value) {
    return false;
  }
  if (manifest.icons.value.length === 0) {
    return false;
  }
  return true;
}

/**
 * @param {number} sizeRequirement
 * @param {!Manifest} manifest
 * @return {!Array<string>} Value of satisfactory sizes (eg. ['192x192', '256x256'])
 */
function sizeAtLeast(sizeRequirement, manifest) {
  // An icon can be provided for a single size, or for multiple sizes.
  // To handle both, we flatten all found sizes into a single array.
  const iconValues = /** @type {!Array<!ManifestImageNode>} */ (manifest.icons.value);
  const nestedSizes = iconValues.map(icon => icon.value.sizes.value);
  const flattenedSizes = [].concat.apply([], nestedSizes);

  return flattenedSizes
      // First, filter out any undefined values, in case an icon was defined without a size
      .filter(size => typeof size === 'string')
      // discard sizes that are not AAxBB (eg. "any")
      .filter(size => /\d+x\d+/.test(size))
      .filter(size => {
        // Split the '24x24' strings into ['24','24'] arrays
        const sizeStrs = size.split(/x/i);
        // Cast the ['24','24'] strings into [24,24] numbers
        const sizeNums = [parseFloat(sizeStrs[0]), parseFloat(sizeStrs[1])];
        // Only keep sizes that are as big as our required size
        const areIconsBigEnough = sizeNums[0] >= sizeRequirement && sizeNums[1] >= sizeRequirement;
        // Square is required: https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/manifest/manifest_icon_selector.cc&q=ManifestIconSelector::IconSizesContainsBiggerThanMinimumSize&sq=package:chromium
        const areIconsSquare = sizeNums[0] === sizeNums[1];
        return areIconsBigEnough && areIconsSquare;
      });
}

module.exports = {
  doExist,
  sizeAtLeast
};