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Twitch - Disable automatic video downscale

Disables the automatic downscaling of Twitch streams while tabbed away

// ==UserScript==
// @name         Twitch - Disable automatic video downscale
// @namespace    CommanderRoot
// @copyright    CommanderRoot
// @license      Unlicense
// @version      1.2.5
// @description  Disables the automatic downscaling of Twitch streams while tabbed away
// @author       https://twitter.com/CommanderRoot
// @match        https://www.twitch.tv/*
// @match        https://m.twitch.tv/*
// @match        https://player.twitch.tv/*
// @grant        none
// @run-at       document-start
// ==/UserScript==
"use strict";

// Try to trick the site into thinking it's never hidden
Object.defineProperty(document, 'visibilityState', { value: 'visible', writable: false });
Object.defineProperty(document, 'webkitVisibilityState', { value: 'visible', writable: false });
document.hasFocus = function () { return true; };
document.dispatchEvent(new Event('visibilitychange'));
const initialHidden = document.hidden;
let didInitialPlay = false;
let lastVideoPlaying = null;

// visibilitychange events are captured and stopped
document.addEventListener('visibilitychange', function (e) {
  if (initialHidden === true && didInitialPlay === false) {
    // Allow propagation to prevent black screen when a stream was opened in a new tab
  } else {
    e.stopImmediatePropagation();
  }

  // Try to play the video on Chrome
  if (typeof chrome !== 'undefined') {
    if (document.hidden) {
      const videos = document.getElementsByTagName('video');
      if (videos.length > 0) {
        lastVideoPlaying = !videos[0].paused && !videos[0].ended;
      } else {
        lastVideoPlaying = false;
      }
    } else {
      playVideo();
    }
  }
}, true);

function setQualitySettings() {
  // Set the player quality to "Source"
  try {
    window.localStorage.setItem('s-qs-ts', Math.floor(Date.now()));
    window.localStorage.setItem('video-quality', '{"default":"chunked"}');
  } catch (e) {
    console.log(e);
  }
}

function playVideo() {
  const videos = document.getElementsByTagName('video');
  if (videos.length > 0) {
    if ((didInitialPlay === false || lastVideoPlaying === true) && !videos[0].ended) {
      videos[0].play();
      didInitialPlay = true;
    }
  }
}

setQualitySettings();

// Add event handler for when we switch between pages
// This is useful when we switch for example from a Clip
// without "Source" to a livestream
window.addEventListener('popstate', () => {
  setQualitySettings();
});