Add plugin to control playback speed like in YouTube (from 0.25 to 2)

plugins/playback-speed/front.js

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+const { watchDOMElement } = require("../../providers/dom-elements");
+const { ElementFromFile, templatePath } = require("../utils");
+
+const slider = ElementFromFile(templatePath(__dirname, "slider.html"));
+
+const MIN_PLAYBACK_SPEED = 0.25;
+const MAX_PLAYBACK_SPEED = 2;
+
+let videoElement;
+let playbackSpeedPercentage = 50; // = Playback speed of 1
+
+const computePlayBackSpeed = () => {
+	if (playbackSpeedPercentage <= 50) {
+		// Slow down video by setting a playback speed between MIN_PLAYBACK_SPEED and 1
+		return (
+			MIN_PLAYBACK_SPEED +
+			((1 - MIN_PLAYBACK_SPEED) / 50) * playbackSpeedPercentage
+		);
+	}
+
+	// Accelerate video by setting a playback speed between 1 and MAX_PLAYBACK_SPEED
+	return 1 + ((MAX_PLAYBACK_SPEED - 1) / 50) * (playbackSpeedPercentage - 50);
+};
+
+const updatePlayBackSpeed = () => {
+	const playbackSpeed = Math.round(computePlayBackSpeed() * 100) / 100;
+
+	if (!videoElement || videoElement.playbackRate === playbackSpeed) {
+		return;
+	}
+
+	videoElement.playbackRate = playbackSpeed;
+
+	const playbackSpeedElement = document.querySelector("#playback-speed-value");
+	if (playbackSpeedElement) {
+		playbackSpeedElement.innerHTML = playbackSpeed;
+	}
+};
+
+module.exports = () => {
+	watchDOMElement(
+		"video",
+		(document) => document.querySelector("video"),
+		(element) => {
+			videoElement = element;
+			updatePlayBackSpeed();
+		}
+	);
+
+	watchDOMElement(
+		"menu",
+		(document) =>
+			document.querySelector("ytmusic-menu-popup-renderer paper-listbox"),
+		(menuElement) => {
+			if (!menuElement.contains(slider)) {
+				menuElement.prepend(slider);
+			}
+
+			const playbackSpeedElement = document.querySelector(
+				"#playback-speed-slider #sliderKnob .slider-knob-inner"
+			);
+
+			const playbackSpeedObserver = new MutationObserver((mutations) => {
+				mutations.forEach(function (mutation) {
+					if (mutation.type == "attributes") {
+						const value = playbackSpeedElement.getAttribute("value");
+						playbackSpeedPercentage = parseInt(value, 10);
+						if (isNaN(playbackSpeedPercentage)) {
+							playbackSpeedPercentage = 50;
+						}
+						updatePlayBackSpeed();
+						return;
+					}
+				});
+			});
+			playbackSpeedObserver.observe(playbackSpeedElement, {
+				attributes: true,
+			});
+		}
+	);
+};

plugins/playback-speed/templates/slider.html

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+<div
+	class="menu-item ytmusic-menu-popup-renderer"
+	role="option"
+	tabindex="-1"
+	aria-disabled="false"
+	aria-selected="false"
+>
+	<paper-slider
+		id="playback-speed-slider"
+		class="volume-slider style-scope ytmusic-player-bar on-hover"
+		max="100"
+		min="0"
+		step="5"
+		dir="ltr"
+		title="Playback speed"
+		aria-label="Playback speed"
+		role="slider"
+		tabindex="0"
+		aria-valuemin="0"
+		aria-valuemax="100"
+		aria-valuenow="50"
+		aria-disabled="false"
+		value="50"
+		><!--css-build:shady-->
+		<div id="sliderContainer" class="style-scope paper-slider">
+			<div class="bar-container style-scope paper-slider">
+				<paper-progress
+					id="sliderBar"
+					aria-hidden="true"
+					class="style-scope paper-slider"
+					role="progressbar"
+					value="50"
+					aria-valuenow="50"
+					aria-valuemin="0"
+					aria-valuemax="100"
+					aria-disabled="false"
+					style="touch-action: none;"
+					><!--css-build:shady-->
+
+					<div id="progressContainer" class="style-scope paper-progress">
+						<div
+							id="secondaryProgress"
+							class="style-scope paper-progress"
+							hidden="true"
+							style="transform: scaleX(0);"
+						></div>
+						<div
+							id="primaryProgress"
+							class="style-scope paper-progress"
+							style="transform: scaleX(0.5);"
+						></div>
+					</div>
+				</paper-progress>
+			</div>
+			<dom-if class="style-scope paper-slider"
+				><template is="dom-if"></template
+			></dom-if>
+			<div
+				id="sliderKnob"
+				class="slider-knob style-scope paper-slider"
+				style="left: 50%; touch-action: none;"
+			>
+				<div
+					class="slider-knob-inner style-scope paper-slider"
+					value="50"
+				></div>
+				<paper-ripple
+					id="ink"
+					center=""
+					class="circle style-scope paper-slider"
+					style="display: none;"
+					><!--css-build:shady-->
+
+					<div
+						id="background"
+						class="style-scope paper-ripple"
+						style="opacity: 0.006008;"
+					></div>
+					<div id="waves" class="style-scope paper-ripple"></div>
+				</paper-ripple>
+			</div>
+		</div>
+		<dom-if class="style-scope paper-slider"
+			><template is="dom-if"></template
+		></dom-if>
+	</paper-slider>
+
+	<div
+		class="text style-scope ytmusic-toggle-menu-service-item-renderer"
+		id="ytmcustom-playback-speed"
+	>
+		Speed (<span id="playback-speed-value">1</span>)
+	</div>
+</div>

providers/dom-elements.js

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+let domElements = {};
+
+const watchDOMElement = (name, selectorFn, cb) => {
+	const observer = new MutationObserver((mutations, observer) => {
+		if (!domElements[name]) {
+			domElements[name] = selectorFn(document);
+		}
+
+		if (domElements[name]) {
+			cb(domElements[name]);
+		}
+	});
+
+	observer.observe(document, {
+		childList: true,
+		subtree: true,
+	});
+};
+
+module.exports = { watchDOMElement };