mirror of https://github.com/jitsi/jitsi-meet
ref(screenshot-capture): move screenshot processing on a web worker (#14015)
Improvement for the screenshot capture feature by using a web worker to process the differences between the screenshots, and some code adjustments.pull/14038/head jitsi-meet_9080
Gabriel Borlea
1 year ago
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GitHub
parent
0b6705610c
commit
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@ -1,40 +1,44 @@ |
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/** |
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* Percent of pixels that signal if two images should be considered different. |
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*/ |
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export const PERCENTAGE_LOWER_BOUND = 5; |
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export const PERCENTAGE_LOWER_BOUND = 4; |
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/** |
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* Number of milliseconds that represent how often screenshots should be taken. |
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*/ |
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export const POLL_INTERVAL = 4000; |
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export const POLL_INTERVAL = 2000; |
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/** |
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* SET_INTERVAL constant is used to set interval and it is set in |
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* SET_TIMEOUT constant is used to set interval and it is set in |
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* the id property of the request.data property. TimeMs property must |
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* also be set. Request.data example: |
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* |
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* { |
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* id: SET_INTERVAL, |
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* id: SET_TIMEOUT, |
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* timeMs: 33 |
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* }. |
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*/ |
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export const SET_INTERVAL = 1; |
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export const SET_TIMEOUT = 1; |
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/** |
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* CLEAR_INTERVAL constant is used to clear the interval and it is set in |
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* CLEAR_TIMEOUT constant is used to clear the interval and it is set in |
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* the id property of the request.data property. |
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* |
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* { |
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* id: CLEAR_INTERVAL |
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* id: CLEAR_TIMEOUT |
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* }. |
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*/ |
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export const CLEAR_INTERVAL = 2; |
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export const CLEAR_TIMEOUT = 2; |
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/** |
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* INTERVAL_TIMEOUT constant is used as response and it is set in the id property. |
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* TIMEOUT_TICK constant is used as response and it is set in the id property. |
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* |
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* { |
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* id: INTERVAL_TIMEOUT |
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* id: TIMEOUT_TICK |
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* }. |
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*/ |
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export const INTERVAL_TIMEOUT = 3; |
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export const TIMEOUT_TICK = 3; |
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export const SCREENSHOT_QUEUE_LIMIT = 3; |
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export const MAX_FILE_SIZE = 1000000; |
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@ -1,10 +1,10 @@ |
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/** |
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* Helper method used to process screenshots captured by the {@code ScreenshotCaptureEffect}. |
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* |
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* @param {HTMLCanvasElement} canvas - The canvas containing a screenshot to be processed. |
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* @param {Blob} imageBlob - The blob of the screenshot that has to be processed. |
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* @param {Object} options - Custom options required for processing. |
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* @returns {void} |
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* @returns {Promise<void>} |
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*/ |
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export function processScreenshot(canvas, options) { // eslint-disable-line no-unused-vars
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export async function processScreenshot(imageBlob, options) { // eslint-disable-line no-unused-vars
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return; |
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} |
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@ -1,29 +1,132 @@ |
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import pixelmatch from 'pixelmatch'; |
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import { |
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CLEAR_INTERVAL, |
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INTERVAL_TIMEOUT, |
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SET_INTERVAL |
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CLEAR_TIMEOUT, |
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MAX_FILE_SIZE, |
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PERCENTAGE_LOWER_BOUND, |
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SET_TIMEOUT, |
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TIMEOUT_TICK |
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} from './constants'; |
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const code = ` |
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var timer; |
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onmessage = function(request) { |
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switch (request.data.id) { |
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case ${SET_INTERVAL}: { |
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timer = setInterval(() => { |
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postMessage({ id: ${INTERVAL_TIMEOUT} }); |
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}, request.data.timeMs); |
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break; |
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} |
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case ${CLEAR_INTERVAL}: { |
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if (timer) { |
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clearInterval(timer); |
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let timer: ReturnType<typeof setTimeout>; |
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const canvas = new OffscreenCanvas(0, 0); |
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const ctx = canvas.getContext('2d'); |
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let storedImageData: ImageData | undefined; |
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/** |
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* Sends Blob with the screenshot to main thread. |
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* |
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* @param {ImageData} imageData - The image of the screenshot. |
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* @returns {void} |
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*/ |
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async function sendBlob(imageData: ImageData) { |
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let imageBlob = await canvas.convertToBlob({ type: 'image/jpeg' }); |
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if (imageBlob.size > MAX_FILE_SIZE) { |
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const quality = Number((MAX_FILE_SIZE / imageBlob.size).toFixed(2)) * 0.92; |
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imageBlob = await canvas.convertToBlob({ type: 'image/jpeg', |
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quality }); |
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} |
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storedImageData = imageData; |
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postMessage({ |
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id: TIMEOUT_TICK, |
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imageBlob |
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}); |
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} |
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/** |
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* Sends empty message to main thread. |
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* |
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* @returns {void} |
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*/ |
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function sendEmpty() { |
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postMessage({ |
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id: TIMEOUT_TICK |
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}); |
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} |
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/** |
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* Draws the image bitmap on the canvas and checks the difference percent with the previous image |
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* if there is no previous image the percentage is not calculated. |
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* |
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* @param {ImageBitmap} imageBitmap - The image bitmap that is drawn on canvas. |
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* @returns {void} |
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*/ |
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function checkScreenshot(imageBitmap: ImageBitmap) { |
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const { height, width } = imageBitmap; |
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if (canvas.width !== width) { |
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canvas.width = width; |
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} |
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if (canvas.height !== height) { |
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canvas.height = height; |
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} |
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ctx?.drawImage(imageBitmap, 0, 0, width, height); |
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const imageData = ctx?.getImageData(0, 0, width, height); |
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imageBitmap.close(); |
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if (!imageData) { |
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sendEmpty(); |
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return; |
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} |
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if (!storedImageData || imageData.data.length !== storedImageData.data.length) { |
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sendBlob(imageData); |
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return; |
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} |
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let numOfPixels = 0; |
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try { |
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numOfPixels = pixelmatch( |
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imageData.data, |
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storedImageData.data, |
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null, |
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width, |
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height); |
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} catch { |
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sendEmpty(); |
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return; |
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} |
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const percent = numOfPixels / imageData.data.length * 100; |
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if (percent >= PERCENTAGE_LOWER_BOUND) { |
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sendBlob(imageData); |
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} else { |
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sendEmpty(); |
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} |
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} |
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onmessage = function(request) { |
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switch (request.data.id) { |
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case SET_TIMEOUT: { |
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timer = setTimeout(async () => { |
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const imageBitmap = request.data.imageBitmap; |
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if (imageBitmap) { |
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checkScreenshot(imageBitmap); |
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} else { |
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sendEmpty(); |
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} |
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break; |
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} |
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}, request.data.timeMs); |
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break; |
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} |
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case CLEAR_TIMEOUT: { |
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if (timer) { |
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clearTimeout(timer); |
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} |
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}; |
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`;
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// @ts-ignore
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export const timerWorkerScript = URL.createObjectURL(new Blob([ code ], { type: 'application/javascript' })); |
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break; |
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} |
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} |
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}; |
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