@wordpress/block-library/build-module/cover/edit/use-cover-is-dark.js

Block library for the WordPress editor.

/**
 * External dependencies
 */
import { FastAverageColor } from 'fast-average-color';
import { colord } from 'colord';
/**
 * WordPress dependencies
 */

import { useEffect, useState } from '@wordpress/element';

function retrieveFastAverageColor() {
  if (!retrieveFastAverageColor.fastAverageColor) {
    retrieveFastAverageColor.fastAverageColor = new FastAverageColor();
  }

  return retrieveFastAverageColor.fastAverageColor;
}
/**
 * useCoverIsDark is a hook that returns a boolean variable specifying if the cover
 * background is dark or not.
 *
 * @param {?string} url          Url of the media background.
 * @param {?number} dimRatio     Transparency of the overlay color. If an image and
 *                               color are set, dimRatio is used to decide what is used
 *                               for background darkness checking purposes.
 * @param {?string} overlayColor String containing the overlay color value if one exists.
 * @param {?Object} elementRef   If a media background is set, elementRef should contain a reference to a
 *                               dom element that renders that media.
 *
 * @return {boolean} True if the cover background is considered "dark" and false otherwise.
 */


export default function useCoverIsDark(url) {
  let dimRatio = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 50;
  let overlayColor = arguments.length > 2 ? arguments[2] : undefined;
  let elementRef = arguments.length > 3 ? arguments[3] : undefined;
  const [isDark, setIsDark] = useState(false);
  useEffect(() => {
    // If opacity is lower than 50 the dominant color is the image or video color,
    // so use that color for the dark mode computation.
    if (url && dimRatio <= 50 && elementRef.current) {
      retrieveFastAverageColor().getColorAsync(elementRef.current, {
        // Previously the default color was white, but that changed
        // in v6.0.0 so it has to be manually set now.
        defaultColor: [255, 255, 255, 255],
        // Errors that come up don't reject the promise, so error
        // logging has to be silenced with this option.
        silent: process.env.NODE_ENV === 'production'
      }).then(color => setIsDark(color.isDark));
    }
  }, [url, url && dimRatio <= 50 && elementRef.current, setIsDark]);
  useEffect(() => {
    // If opacity is greater than 50 the dominant color is the overlay color,
    // so use that color for the dark mode computation.
    if (dimRatio > 50 || !url) {
      if (!overlayColor) {
        // If no overlay color exists the overlay color is black (isDark )
        setIsDark(true);
        return;
      }

      setIsDark(colord(overlayColor).isDark());
    }
  }, [overlayColor, dimRatio > 50 || !url, setIsDark]);
  useEffect(() => {
    if (!url && !overlayColor) {
      // Reset isDark.
      setIsDark(false);
    }
  }, [!url && !overlayColor, setIsDark]);
  return isDark;
}
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