49 lines
1.3 KiB
JavaScript
49 lines
1.3 KiB
JavaScript
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// @flow
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import { isIconUrl } from './functions';
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/**
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* Tries to preload an image.
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*
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* @param {string | Object} src - Source of the avatar.
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* @param {boolean} useCORS - Whether to use CORS or not.
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* @param {boolean} tryOnce - If true we try to load the image only using the specified CORS mode. Otherwise both modes
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* (CORS and no CORS) will be used to load the image if the first attempt fails.
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* @returns {Promise}
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*/
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export function preloadImage(
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src: string | Object,
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useCORS: ?boolean = false,
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tryOnce: ?boolean = false
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): Promise<Object> {
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if (isIconUrl(src)) {
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return Promise.resolve({ src });
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}
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return new Promise((resolve, reject) => {
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const image = document.createElement('img');
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if (useCORS) {
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image.setAttribute('crossOrigin', '');
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}
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image.onload = () => resolve({
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src,
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isUsingCORS: useCORS
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});
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image.onerror = error => {
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if (tryOnce) {
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reject(error);
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} else {
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preloadImage(src, !useCORS, true)
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.then(resolve)
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.catch(reject);
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}
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};
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// $FlowExpectedError
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image.referrerPolicy = 'no-referrer';
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image.src = src;
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});
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}
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