10 files changed, 1255 insertions, 455 deletions

diff --git a/platform/javascript/js/engine/config.js b/platform/javascript/js/engine/config.js
index 97fd718815..82ff273ecf 100644
--- a/platform/javascript/js/engine/config.js
+++ b/platform/javascript/js/engine/config.js
@@ -1,100 +1,320 @@
-/** @constructor */
-function EngineConfig(opts) {
-	// Module config
-	this.unloadAfterInit = true;
-	this.onPrintError = function () {
-		console.error.apply(console, Array.from(arguments)); // eslint-disable-line no-console
-	};
-	this.onPrint = function () {
-		console.log.apply(console, Array.from(arguments)); // eslint-disable-line no-console
+/**
+ * An object used to configure the Engine instance based on godot export options, and to override those in custom HTML
+ * templates if needed.
+ *
+ * @header Engine configuration
+ * @summary The Engine configuration object. This is just a typedef, create it like a regular object, e.g.:
+ *
+ * ``const MyConfig = { executable: 'godot', unloadAfterInit: false }``
+ *
+ * @typedef {Object} EngineConfig
+ */
+const EngineConfig = {}; // eslint-disable-line no-unused-vars
+
+/**
+ * @struct
+ * @constructor
+ * @ignore
+ */
+const InternalConfig = function (initConfig) { // eslint-disable-line no-unused-vars
+	const cfg = /** @lends {InternalConfig.prototype} */ {
+		/**
+		 * Whether the unload the engine automatically after the instance is initialized.
+		 *
+		 * @memberof EngineConfig
+		 * @default
+		 * @type {boolean}
+		 */
+		unloadAfterInit: true,
+		/**
+		 * The HTML DOM Canvas object to use.
+		 *
+		 * By default, the first canvas element in the document will be used is none is specified.
+		 *
+		 * @memberof EngineConfig
+		 * @default
+		 * @type {?HTMLCanvasElement}
+		 */
+		canvas: null,
+		/**
+		 * The name of the WASM file without the extension. (Set by Godot Editor export process).
+		 *
+		 * @memberof EngineConfig
+		 * @default
+		 * @type {string}
+		 */
+		executable: '',
+		/**
+		 * An alternative name for the game pck to load. The executable name is used otherwise.
+		 *
+		 * @memberof EngineConfig
+		 * @default
+		 * @type {?string}
+		 */
+		mainPack: null,
+		/**
+		 * Specify a language code to select the proper localization for the game.
+		 *
+		 * The browser locale will be used if none is specified. See complete list of
+		 * :ref:`supported locales <doc_locales>`.
+		 *
+		 * @memberof EngineConfig
+		 * @type {?string}
+		 * @default
+		 */
+		locale: null,
+		/**
+		 * The canvas resize policy determines how the canvas should be resized by Godot.
+		 *
+		 * ``0`` means Godot won't do any resizing. This is useful if you want to control the canvas size from
+		 * javascript code in your template.
+		 *
+		 * ``1`` means Godot will resize the canvas on start, and when changing window size via engine functions.
+		 *
+		 * ``2`` means Godot will adapt the canvas size to match the whole browser window.
+		 *
+		 * @memberof EngineConfig
+		 * @type {number}
+		 * @default
+		 */
+		canvasResizePolicy: 2,
+		/**
+		 * The arguments to be passed as command line arguments on startup.
+		 *
+		 * See :ref:`command line tutorial <doc_command_line_tutorial>`.
+		 *
+		 * **Note**: :js:meth:`startGame <Engine.prototype.startGame>` will always add the ``--main-pack`` argument.
+		 *
+		 * @memberof EngineConfig
+		 * @type {Array<string>}
+		 * @default
+		 */
+		args: [],
+		/**
+		 * @ignore
+		 * @type {Array.<string>}
+		 */
+		persistentPaths: ['/userfs'],
+		/**
+		 * @ignore
+		 * @type {Array.<string>}
+		 */
+		gdnativeLibs: [],
+		/**
+		 * @ignore
+		 * @type {Array.<string>}
+		 */
+		fileSizes: [],
+		/**
+		 * A callback function for handling Godot's ``OS.execute`` calls.
+		 *
+		 * This is for example used in the Web Editor template to switch between project manager and editor, and for running the game.
+		 *
+		 * @callback EngineConfig.onExecute
+		 * @param {string} path The path that Godot's wants executed.
+		 * @param {Array.<string>} args The arguments of the "command" to execute.
+		 */
+		/**
+		 * @ignore
+		 * @type {?function(string, Array.<string>)}
+		 */
+		onExecute: null,
+		/**
+		 * A callback function for being notified when the Godot instance quits.
+		 *
+		 * **Note**: This function will not be called if the engine crashes or become unresponsive.
+		 *
+		 * @callback EngineConfig.onExit
+		 * @param {number} status_code The status code returned by Godot on exit.
+		 */
+		/**
+		 * @ignore
+		 * @type {?function(number)}
+		 */
+		onExit: null,
+		/**
+		 * A callback function for displaying download progress.
+		 *
+		 * The function is called once per frame while downloading files, so the usage of ``requestAnimationFrame()``
+		 * is not necessary.
+		 *
+		 * If the callback function receives a total amount of bytes as 0, this means that it is impossible to calculate.
+		 * Possible reasons include:
+		 *
+		 * -  Files are delivered with server-side chunked compression
+		 * -  Files are delivered with server-side compression on Chromium
+		 * -  Not all file downloads have started yet (usually on servers without multi-threading)
+		 *
+		 * @callback EngineConfig.onProgress
+		 * @param {number} current The current amount of downloaded bytes so far.
+		 * @param {number} total The total amount of bytes to be downloaded.
+		 */
+		/**
+		 * @ignore
+		 * @type {?function(number, number)}
+		 */
+		onProgress: null,
+		/**
+		 * A callback function for handling the standard output stream. This method should usually only be used in debug pages.
+		 *
+		 * By default, ``console.log()`` is used.
+		 *
+		 * @callback EngineConfig.onPrint
+		 * @param {...*} [var_args] A variadic number of arguments to be printed.
+		 */
+		/**
+		 * @ignore
+		 * @type {?function(...*)}
+		 */
+		onPrint: function () {
+			console.log.apply(console, Array.from(arguments)); // eslint-disable-line no-console
+		},
+		/**
+		 * A callback function for handling the standard error stream. This method should usually only be used in debug pages.
+		 *
+		 * By default, ``console.error()`` is used.
+		 *
+		 * @callback EngineConfig.onPrintError
+		 * @param {...*} [var_args] A variadic number of arguments to be printed as errors.
+		*/
+		/**
+		 * @ignore
+		 * @type {?function(...*)}
+		 */
+		onPrintError: function (var_args) {
+			console.error.apply(console, Array.from(arguments)); // eslint-disable-line no-console
+		},
 	};
-	this.onProgress = null;
 
-	// Godot Config
-	this.canvas = null;
-	this.executable = '';
-	this.mainPack = null;
-	this.locale = null;
-	this.canvasResizePolicy = false;
-	this.persistentPaths = ['/userfs'];
-	this.gdnativeLibs = [];
-	this.args = [];
-	this.onExecute = null;
-	this.onExit = null;
-	this.update(opts);
-}
+	/**
+	 * @ignore
+	 * @struct
+	 * @constructor
+	 * @param {EngineConfig} opts
+	 */
+	function Config(opts) {
+		this.update(opts);
+	}
+
+	Config.prototype = cfg;
 
-EngineConfig.prototype.update = function (opts) {
-	const config = opts || {};
-	function parse(key, def) {
-		if (typeof (config[key]) === 'undefined') {
-			return def;
+	/**
+	 * @ignore
+	 * @param {EngineConfig} opts
+	 */
+	Config.prototype.update = function (opts) {
+		const config = opts || {};
+		function parse(key, def) {
+			if (typeof (config[key]) === 'undefined') {
+				return def;
+			}
+			return config[key];
 		}
-		return config[key];
-	}
-	// Module config
-	this.unloadAfterInit = parse('unloadAfterInit', this.unloadAfterInit);
-	this.onPrintError = parse('onPrintError', this.onPrintError);
-	this.onPrint = parse('onPrint', this.onPrint);
-	this.onProgress = parse('onProgress', this.onProgress);
+		// Module config
+		this.unloadAfterInit = parse('unloadAfterInit', this.unloadAfterInit);
+		this.onPrintError = parse('onPrintError', this.onPrintError);
+		this.onPrint = parse('onPrint', this.onPrint);
+		this.onProgress = parse('onProgress', this.onProgress);
 
-	// Godot config
-	this.canvas = parse('canvas', this.canvas);
-	this.executable = parse('executable', this.executable);
-	this.mainPack = parse('mainPack', this.mainPack);
-	this.locale = parse('locale', this.locale);
-	this.canvasResizePolicy = parse('canvasResizePolicy', this.canvasResizePolicy);
-	this.persistentPaths = parse('persistentPaths', this.persistentPaths);
-	this.gdnativeLibs = parse('gdnativeLibs', this.gdnativeLibs);
-	this.args = parse('args', this.args);
-	this.onExecute = parse('onExecute', this.onExecute);
-	this.onExit = parse('onExit', this.onExit);
-};
+		// Godot config
+		this.canvas = parse('canvas', this.canvas);
+		this.executable = parse('executable', this.executable);
+		this.mainPack = parse('mainPack', this.mainPack);
+		this.locale = parse('locale', this.locale);
+		this.canvasResizePolicy = parse('canvasResizePolicy', this.canvasResizePolicy);
+		this.persistentPaths = parse('persistentPaths', this.persistentPaths);
+		this.gdnativeLibs = parse('gdnativeLibs', this.gdnativeLibs);
+		this.fileSizes = parse('fileSizes', this.fileSizes);
+		this.args = parse('args', this.args);
+		this.onExecute = parse('onExecute', this.onExecute);
+		this.onExit = parse('onExit', this.onExit);
+	};
 
-EngineConfig.prototype.getModuleConfig = function (loadPath, loadPromise) {
-	const me = this;
-	return {
-		'print': this.onPrint,
-		'printErr': this.onPrintError,
-		'locateFile': Utils.createLocateRewrite(loadPath),
-		'instantiateWasm': Utils.createInstantiatePromise(loadPromise),
-		'thisProgram': me.executable,
-		'noExitRuntime': true,
-		'dynamicLibraries': [`${me.executable}.side.wasm`],
+	/**
+	 * @ignore
+	 * @param {string} loadPath
+	 * @param {Response} response
+	 */
+	Config.prototype.getModuleConfig = function (loadPath, response) {
+		let r = response;
+		return {
+			'print': this.onPrint,
+			'printErr': this.onPrintError,
+			'thisProgram': this.executable,
+			'noExitRuntime': true,
+			'dynamicLibraries': [`${loadPath}.side.wasm`],
+			'instantiateWasm': function (imports, onSuccess) {
+				function done(result) {
+					onSuccess(result['instance'], result['module']);
+				}
+				if (typeof (WebAssembly.instantiateStreaming) !== 'undefined') {
+					WebAssembly.instantiateStreaming(Promise.resolve(r), imports).then(done);
+				} else {
+					r.arrayBuffer().then(function (buffer) {
+						WebAssembly.instantiate(buffer, imports).then(done);
+					});
+				}
+				r = null;
+				return {};
+			},
+			'locateFile': function (path) {
+				if (path.endsWith('.worker.js')) {
+					return `${loadPath}.worker.js`;
+				} else if (path.endsWith('.audio.worklet.js')) {
+					return `${loadPath}.audio.worklet.js`;
+				} else if (path.endsWith('.js')) {
+					return `${loadPath}.js`;
+				} else if (path.endsWith('.side.wasm')) {
+					return `${loadPath}.side.wasm`;
+				} else if (path.endsWith('.wasm')) {
+					return `${loadPath}.wasm`;
+				}
+				return path;
+			},
+		};
 	};
-};
 
-EngineConfig.prototype.getGodotConfig = function (cleanup) {
-	if (!(this.canvas instanceof HTMLCanvasElement)) {
-		this.canvas = Utils.findCanvas();
-		if (!this.canvas) {
-			throw new Error('No canvas found in page');
+	/**
+	 * @ignore
+	 * @param {function()} cleanup
+	 */
+	Config.prototype.getGodotConfig = function (cleanup) {
+		// Try to find a canvas
+		if (!(this.canvas instanceof HTMLCanvasElement)) {
+			const nodes = document.getElementsByTagName('canvas');
+			if (nodes.length && nodes[0] instanceof HTMLCanvasElement) {
+				this.canvas = nodes[0];
+			}
+			if (!this.canvas) {
+				throw new Error('No canvas found in page');
+			}
+		}
+		// Canvas can grab focus on click, or key events won't work.
+		if (this.canvas.tabIndex < 0) {
+			this.canvas.tabIndex = 0;
 		}
-	}
 
-	// Canvas can grab focus on click, or key events won't work.
-	if (this.canvas.tabIndex < 0) {
-		this.canvas.tabIndex = 0;
-	}
+		// Browser locale, or custom one if defined.
+		let locale = this.locale;
+		if (!locale) {
+			locale = navigator.languages ? navigator.languages[0] : navigator.language;
+			locale = locale.split('.')[0];
+		}
+		const onExit = this.onExit;
 
-	// Browser locale, or custom one if defined.
-	let locale = this.locale;
-	if (!locale) {
-		locale = navigator.languages ? navigator.languages[0] : navigator.language;
-		locale = locale.split('.')[0];
-	}
-	const onExit = this.onExit;
-	// Godot configuration.
-	return {
-		'canvas': this.canvas,
-		'canvasResizePolicy': this.canvasResizePolicy,
-		'locale': locale,
-		'onExecute': this.onExecute,
-		'onExit': function (p_code) {
-			cleanup(); // We always need to call the cleanup callback to free memory.
-			if (typeof (onExit) === 'function') {
-				onExit(p_code);
-			}
-		},
+		// Godot configuration.
+		return {
+			'canvas': this.canvas,
+			'canvasResizePolicy': this.canvasResizePolicy,
+			'locale': locale,
+			'onExecute': this.onExecute,
+			'onExit': function (p_code) {
+				cleanup(); // We always need to call the cleanup callback to free memory.
+				if (typeof (onExit) === 'function') {
+					onExit(p_code);
+				}
+			},
+		};
 	};
+	return new Config(initConfig);
 };
diff --git a/platform/javascript/js/engine/engine.externs.js b/platform/javascript/js/engine/engine.externs.js
index 1a94dd15ec..35a66a93ae 100644
--- a/platform/javascript/js/engine/engine.externs.js
+++ b/platform/javascript/js/engine/engine.externs.js
@@ -1,3 +1,4 @@
 var Godot;
 var WebAssembly = {};
 WebAssembly.instantiate = function(buffer, imports) {};
+WebAssembly.instantiateStreaming = function(response, imports) {};
diff --git a/platform/javascript/js/engine/engine.js b/platform/javascript/js/engine/engine.js
index d14e0e5806..19a0552c8c 100644
--- a/platform/javascript/js/engine/engine.js
+++ b/platform/javascript/js/engine/engine.js
@@ -1,3 +1,13 @@
+/**
+ * Projects exported for the Web expose the :js:class:`Engine` class to the JavaScript environment, that allows
+ * fine control over the engine's start-up process.
+ *
+ * This API is built in an asynchronous manner and requires basic understanding
+ * of `Promises <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises>`__.
+ *
+ * @module Engine
+ * @header HTML5 shell class reference
+ */
 const Engine = (function () {
 	const preloader = new Preloader();
 
@@ -5,139 +15,259 @@ const Engine = (function () {
 	let loadPath = '';
 	let initPromise = null;
 
-	function load(basePath) {
+	/**
+	 * @classdesc The ``Engine`` class provides methods for loading and starting exported projects on the Web. For default export
+	 * settings, this is already part of the exported HTML page. To understand practical use of the ``Engine`` class,
+	 * see :ref:`Custom HTML page for Web export <doc_customizing_html5_shell>`.
+	 *
+	 * @description Create a new Engine instance with the given configuration.
+	 *
+	 * @global
+	 * @constructor
+	 * @param {EngineConfig} initConfig The initial config for this instance.
+	 */
+	function Engine(initConfig) { // eslint-disable-line no-shadow
+		this.config = new InternalConfig(initConfig);
+		this.rtenv = null;
+	}
+
+	/**
+	 * Load the engine from the specified base path.
+	 *
+	 * @param {string} basePath Base path of the engine to load.
+	 * @param {number=} [size=0] The file size if known.
+	 * @returns {Promise} A Promise that resolves once the engine is loaded.
+	 *
+	 * @function Engine.load
+	 */
+	Engine.load = function (basePath, size) {
 		if (loadPromise == null) {
 			loadPath = basePath;
-			loadPromise = preloader.loadPromise(`${loadPath}.wasm`);
+			loadPromise = preloader.loadPromise(`${loadPath}.wasm`, size, true);
 			requestAnimationFrame(preloader.animateProgress);
 		}
 		return loadPromise;
-	}
+	};
 
-	function unload() {
+	/**
+	 * Unload the engine to free memory.
+	 *
+	 * This method will be called automatically depending on the configuration. See :js:attr:`unloadAfterInit`.
+	 *
+	 * @function Engine.unload
+	 */
+	Engine.unload = function () {
 		loadPromise = null;
-	}
+	};
 
-	/** @constructor */
-	function Engine(opts) { // eslint-disable-line no-shadow
-		this.config = new EngineConfig(opts);
-		this.rtenv = null;
-	}
+	/**
+	 * Check whether WebGL is available. Optionally, specify a particular version of WebGL to check for.
+	 *
+	 * @param {number=} [majorVersion=1] The major WebGL version to check for.
+	 * @returns {boolean} If the given major version of WebGL is available.
+	 * @function Engine.isWebGLAvailable
+	 */
+	Engine.isWebGLAvailable = function (majorVersion = 1) {
+		try {
+			return !!document.createElement('canvas').getContext(['webgl', 'webgl2'][majorVersion - 1]);
+		} catch (e) { /* Not available */ }
+		return false;
+	};
 
-	Engine.prototype.init = /** @param {string=} basePath */ function (basePath) {
-		if (initPromise) {
-			return initPromise;
-		}
-		if (loadPromise == null) {
-			if (!basePath) {
-				initPromise = Promise.reject(new Error('A base path must be provided when calling `init` and the engine is not loaded.'));
+	/**
+	 * Safe Engine constructor, creates a new prototype for every new instance to avoid prototype pollution.
+	 * @ignore
+	 * @constructor
+	 */
+	function SafeEngine(initConfig) {
+		const proto = /** @lends Engine.prototype */ {
+			/**
+			 * Initialize the engine instance. Optionally, pass the base path to the engine to load it,
+			 * if it hasn't been loaded yet. See :js:meth:`Engine.load`.
+			 *
+			 * @param {string=} basePath Base path of the engine to load.
+			 * @return {Promise} A ``Promise`` that resolves once the engine is loaded and initialized.
+			 */
+			init: function (basePath) {
+				if (initPromise) {
+					return initPromise;
+				}
+				if (loadPromise == null) {
+					if (!basePath) {
+						initPromise = Promise.reject(new Error('A base path must be provided when calling `init` and the engine is not loaded.'));
+						return initPromise;
+					}
+					Engine.load(basePath, this.config.fileSizes[`${basePath}.wasm`]);
+				}
+				const me = this;
+				function doInit(promise) {
+					return promise.then(function (response) {
+						return Godot(me.config.getModuleConfig(loadPath, response.clone()));
+					}).then(function (module) {
+						const paths = me.config.persistentPaths;
+						return module['initFS'](paths).then(function (err) {
+							return Promise.resolve(module);
+						});
+					}).then(function (module) {
+						me.rtenv = module;
+						if (me.config.unloadAfterInit) {
+							Engine.unload();
+						}
+						return Promise.resolve();
+					});
+				}
+				preloader.setProgressFunc(this.config.onProgress);
+				initPromise = doInit(loadPromise);
 				return initPromise;
-			}
-			load(basePath);
-		}
-		preloader.setProgressFunc(this.config.onProgress);
-		let config = this.config.getModuleConfig(loadPath, loadPromise);
-		const me = this;
-		initPromise = new Promise(function (resolve, reject) {
-			Godot(config).then(function (module) {
-				module['initFS'](me.config.persistentPaths).then(function (fs_err) {
-					me.rtenv = module;
-					if (me.config.unloadAfterInit) {
-						unload();
+			},
+
+			/**
+			 * Load a file so it is available in the instance's file system once it runs. Must be called **before** starting the
+			 * instance.
+			 *
+			 * If not provided, the ``path`` is derived from the URL of the loaded file.
+			 *
+			 * @param {string|ArrayBuffer} file The file to preload.
+			 *
+			 * If a ``string`` the file will be loaded from that path.
+			 *
+			 * If an ``ArrayBuffer`` or a view on one, the buffer will used as the content of the file.
+			 *
+			 * @param {string=} path Path by which the file will be accessible. Required, if ``file`` is not a string.
+			 *
+			 * @returns {Promise} A Promise that resolves once the file is loaded.
+			 */
+			preloadFile: function (file, path) {
+				return preloader.preload(file, path, this.config.fileSizes[file]);
+			},
+
+			/**
+			 * Start the engine instance using the given override configuration (if any).
+			 * :js:meth:`startGame <Engine.prototype.startGame>` can be used in typical cases instead.
+			 *
+			 * This will initialize the instance if it is not initialized. For manual initialization, see :js:meth:`init <Engine.prototype.init>`.
+			 * The engine must be loaded beforehand.
+			 *
+			 * Fails if a canvas cannot be found on the page, or not specified in the configuration.
+			 *
+			 * @param {EngineConfig} override An optional configuration override.
+			 * @return {Promise} Promise that resolves once the engine started.
+			 */
+			start: function (override) {
+				this.config.update(override);
+				const me = this;
+				return me.init().then(function () {
+					if (!me.rtenv) {
+						return Promise.reject(new Error('The engine must be initialized before it can be started'));
 					}
-					resolve();
-					config = null;
-				});
-			});
-		});
-		return initPromise;
-	};
 
-	/** @type {function(string, string):Object} */
-	Engine.prototype.preloadFile = function (file, path) {
-		return preloader.preload(file, path);
-	};
+					let config = {};
+					try {
+						config = me.config.getGodotConfig(function () {
+							me.rtenv = null;
+						});
+					} catch (e) {
+						return Promise.reject(e);
+					}
+					// Godot configuration.
+					me.rtenv['initConfig'](config);
 
-	/** @type {function(...string):Object} */
-	Engine.prototype.start = function (override) {
-		this.config.update(override);
-		const me = this;
-		return me.init().then(function () {
-			if (!me.rtenv) {
-				return Promise.reject(new Error('The engine must be initialized before it can be started'));
-			}
-
-			let config = {};
-			try {
-				config = me.config.getGodotConfig(function () {
-					me.rtenv = null;
-				});
-			} catch (e) {
-				return Promise.reject(e);
-			}
-			// Godot configuration.
-			me.rtenv['initConfig'](config);
-
-			// Preload GDNative libraries.
-			const libs = [];
-			me.config.gdnativeLibs.forEach(function (lib) {
-				libs.push(me.rtenv['loadDynamicLibrary'](lib, { 'loadAsync': true }));
-			});
-			return Promise.all(libs).then(function () {
-				return new Promise(function (resolve, reject) {
-					preloader.preloadedFiles.forEach(function (file) {
-						me.rtenv['copyToFS'](file.path, file.buffer);
+					// Preload GDNative libraries.
+					const libs = [];
+					me.config.gdnativeLibs.forEach(function (lib) {
+						libs.push(me.rtenv['loadDynamicLibrary'](lib, { 'loadAsync': true }));
+					});
+					return Promise.all(libs).then(function () {
+						return new Promise(function (resolve, reject) {
+							preloader.preloadedFiles.forEach(function (file) {
+								me.rtenv['copyToFS'](file.path, file.buffer);
+							});
+							preloader.preloadedFiles.length = 0; // Clear memory
+							me.rtenv['callMain'](me.config.args);
+							initPromise = null;
+							resolve();
+						});
 					});
-					preloader.preloadedFiles.length = 0; // Clear memory
-					me.rtenv['callMain'](me.config.args);
-					initPromise = null;
-					resolve();
 				});
-			});
-		});
-	};
+			},
 
-	Engine.prototype.startGame = function (override) {
-		this.config.update(override);
-		// Add main-pack argument.
-		const exe = this.config.executable;
-		const pack = this.config.mainPack || `${exe}.pck`;
-		this.config.args = ['--main-pack', pack].concat(this.config.args);
-		// Start and init with execName as loadPath if not inited.
-		const me = this;
-		return Promise.all([
-			this.init(exe),
-			this.preloadFile(pack, pack),
-		]).then(function () {
-			return me.start.apply(me);
-		});
-	};
+			/**
+			 * Start the game instance using the given configuration override (if any).
+			 *
+			 * This will initialize the instance if it is not initialized. For manual initialization, see :js:meth:`init <Engine.prototype.init>`.
+			 *
+			 * This will load the engine if it is not loaded, and preload the main pck.
+			 *
+			 * This method expects the initial config (or the override) to have both the :js:attr:`executable` and :js:attr:`mainPack`
+			 * properties set (normally done by the editor during export).
+			 *
+			 * @param {EngineConfig} override An optional configuration override.
+			 * @return {Promise} Promise that resolves once the game started.
+			 */
+			startGame: function (override) {
+				this.config.update(override);
+				// Add main-pack argument.
+				const exe = this.config.executable;
+				const pack = this.config.mainPack || `${exe}.pck`;
+				this.config.args = ['--main-pack', pack].concat(this.config.args);
+				// Start and init with execName as loadPath if not inited.
+				const me = this;
+				return Promise.all([
+					this.init(exe),
+					this.preloadFile(pack, pack),
+				]).then(function () {
+					return me.start.apply(me);
+				});
+			},
 
-	Engine.prototype.copyToFS = function (path, buffer) {
-		if (this.rtenv == null) {
-			throw new Error('Engine must be inited before copying files');
-		}
-		this.rtenv['copyToFS'](path, buffer);
-	};
+			/**
+			 * Create a file at the specified ``path`` with the passed as ``buffer`` in the instance's file system.
+			 *
+			 * @param {string} path The location where the file will be created.
+			 * @param {ArrayBuffer} buffer The content of the file.
+			 */
+			copyToFS: function (path, buffer) {
+				if (this.rtenv == null) {
+					throw new Error('Engine must be inited before copying files');
+				}
+				this.rtenv['copyToFS'](path, buffer);
+			},
 
-	Engine.prototype.requestQuit = function () {
-		if (this.rtenv) {
-			this.rtenv['request_quit']();
-		}
-	};
+			/**
+			 * Request that the current instance quit.
+			 *
+			 * This is akin the user pressing the close button in the window manager, and will
+			 * have no effect if the engine has crashed, or is stuck in a loop.
+			 *
+			 */
+			requestQuit: function () {
+				if (this.rtenv) {
+					this.rtenv['request_quit']();
+				}
+			},
+		};
+
+		Engine.prototype = proto;
+		// Closure compiler exported instance methods.
+		Engine.prototype['init'] = Engine.prototype.init;
+		Engine.prototype['preloadFile'] = Engine.prototype.preloadFile;
+		Engine.prototype['start'] = Engine.prototype.start;
+		Engine.prototype['startGame'] = Engine.prototype.startGame;
+		Engine.prototype['copyToFS'] = Engine.prototype.copyToFS;
+		Engine.prototype['requestQuit'] = Engine.prototype.requestQuit;
+		// Also expose static methods as instance methods
+		Engine.prototype['load'] = Engine.load;
+		Engine.prototype['unload'] = Engine.unload;
+		Engine.prototype['isWebGLAvailable'] = Engine.isWebGLAvailable;
+		return new Engine(initConfig);
+	}
+
+	// Closure compiler exported static methods.
+	SafeEngine['load'] = Engine.load;
+	SafeEngine['unload'] = Engine.unload;
+	SafeEngine['isWebGLAvailable'] = Engine.isWebGLAvailable;
 
-	// Closure compiler exported engine methods.
-	/** @export */
-	Engine['isWebGLAvailable'] = Utils.isWebGLAvailable;
-	Engine['load'] = load;
-	Engine['unload'] = unload;
-	Engine.prototype['init'] = Engine.prototype.init;
-	Engine.prototype['preloadFile'] = Engine.prototype.preloadFile;
-	Engine.prototype['start'] = Engine.prototype.start;
-	Engine.prototype['startGame'] = Engine.prototype.startGame;
-	Engine.prototype['copyToFS'] = Engine.prototype.copyToFS;
-	Engine.prototype['requestQuit'] = Engine.prototype.requestQuit;
-	return Engine;
+	return SafeEngine;
 }());
 if (typeof window !== 'undefined') {
 	window['Engine'] = Engine;
diff --git a/platform/javascript/js/engine/preloader.js b/platform/javascript/js/engine/preloader.js
index ec34fb93f2..3535fdb361 100644
--- a/platform/javascript/js/engine/preloader.js
+++ b/platform/javascript/js/engine/preloader.js
@@ -1,54 +1,79 @@
 const Preloader = /** @constructor */ function () { // eslint-disable-line no-unused-vars
-	const loadXHR = function (resolve, reject, file, tracker, attempts) {
-		const xhr = new XMLHttpRequest();
+	function getTrackedResponse(response, load_status) {
+		let clen = 0;
+		let compressed = false;
+		response.headers.forEach(function (value, header) {
+			const h = header.toLowerCase().trim();
+			// We can't accurately compute compressed stream length.
+			if (h === 'content-encoding') {
+				compressed = true;
+			} else if (h === 'content-length') {
+				const length = parseInt(value, 10);
+				if (!Number.isNaN(length) && length > 0) {
+					clen = length;
+				}
+			}
+		});
+		if (!compressed && clen) {
+			load_status.total = clen;
+		}
+		function onloadprogress(reader, controller) {
+			return reader.read().then(function (result) {
+				if (load_status.done) {
+					return Promise.resolve();
+				}
+				if (result.value) {
+					controller.enqueue(result.value);
+					load_status.loaded += result.value.length;
+				}
+				if (!result.done) {
+					return onloadprogress(reader, controller);
+				}
+				load_status.done = true;
+				return Promise.resolve();
+			});
+		}
+		const reader = response.body.getReader();
+		return new Response(new ReadableStream({
+			start: function (controller) {
+				onloadprogress(reader, controller).then(function () {
+					controller.close();
+				});
+			},
+		}), { headers: response.headers });
+	}
+
+	function loadFetch(file, tracker, fileSize, raw) {
 		tracker[file] = {
-			total: 0,
+			total: fileSize || 0,
 			loaded: 0,
-			final: false,
+			done: false,
 		};
-		xhr.onerror = function () {
+		return fetch(file).then(function (response) {
+			if (!response.ok) {
+				return Promise.reject(new Error(`Failed loading file '${file}'`));
+			}
+			const tr = getTrackedResponse(response, tracker[file]);
+			if (raw) {
+				return Promise.resolve(tr);
+			}
+			return tr.arrayBuffer();
+		});
+	}
+
+	function retry(func, attempts = 1) {
+		function onerror(err) {
 			if (attempts <= 1) {
-				reject(new Error(`Failed loading file '${file}'`));
-			} else {
+				return Promise.reject(err);
+			}
+			return new Promise(function (resolve, reject) {
 				setTimeout(function () {
-					loadXHR(resolve, reject, file, tracker, attempts - 1);
+					retry(func, attempts - 1).then(resolve).catch(reject);
 				}, 1000);
-			}
-		};
-		xhr.onabort = function () {
-			tracker[file].final = true;
-			reject(new Error(`Loading file '${file}' was aborted.`));
-		};
-		xhr.onloadstart = function (ev) {
-			tracker[file].total = ev.total;
-			tracker[file].loaded = ev.loaded;
-		};
-		xhr.onprogress = function (ev) {
-			tracker[file].loaded = ev.loaded;
-			tracker[file].total = ev.total;
-		};
-		xhr.onload = function () {
-			if (xhr.status >= 400) {
-				if (xhr.status < 500 || attempts <= 1) {
-					reject(new Error(`Failed loading file '${file}': ${xhr.statusText}`));
-					xhr.abort();
-				} else {
-					setTimeout(function () {
-						loadXHR(resolve, reject, file, tracker, attempts - 1);
-					}, 1000);
-				}
-			} else {
-				tracker[file].final = true;
-				resolve(xhr);
-			}
-		};
-		// Make request.
-		xhr.open('GET', file);
-		if (!file.endsWith('.js')) {
-			xhr.responseType = 'arraybuffer';
+			});
 		}
-		xhr.send();
-	};
+		return func().catch(onerror);
+	}
 
 	const DOWNLOAD_ATTEMPTS_MAX = 4;
 	const loadingFiles = {};
@@ -63,7 +88,7 @@ const Preloader = /** @constructor */ function () { // eslint-disable-line no-un
 
 		Object.keys(loadingFiles).forEach(function (file) {
 			const stat = loadingFiles[file];
-			if (!stat.final) {
+			if (!stat.done) {
 				progressIsFinal = false;
 			}
 			if (!totalIsValid || stat.total === 0) {
@@ -92,21 +117,19 @@ const Preloader = /** @constructor */ function () { // eslint-disable-line no-un
 		progressFunc = callback;
 	};
 
-	this.loadPromise = function (file) {
-		return new Promise(function (resolve, reject) {
-			loadXHR(resolve, reject, file, loadingFiles, DOWNLOAD_ATTEMPTS_MAX);
-		});
+	this.loadPromise = function (file, fileSize, raw = false) {
+		return retry(loadFetch.bind(null, file, loadingFiles, fileSize, raw), DOWNLOAD_ATTEMPTS_MAX);
 	};
 
 	this.preloadedFiles = [];
-	this.preload = function (pathOrBuffer, destPath) {
+	this.preload = function (pathOrBuffer, destPath, fileSize) {
 		let buffer = null;
 		if (typeof pathOrBuffer === 'string') {
 			const me = this;
-			return this.loadPromise(pathOrBuffer).then(function (xhr) {
+			return this.loadPromise(pathOrBuffer, fileSize).then(function (buf) {
 				me.preloadedFiles.push({
 					path: destPath || pathOrBuffer,
-					buffer: xhr.response,
+					buffer: buf,
 				});
 				return Promise.resolve();
 			});
diff --git a/platform/javascript/js/engine/utils.js b/platform/javascript/js/engine/utils.js
deleted file mode 100644
index 9273bbad42..0000000000
--- a/platform/javascript/js/engine/utils.js
+++ /dev/null
@@ -1,58 +0,0 @@
-const Utils = { // eslint-disable-line no-unused-vars
-
-	createLocateRewrite: function (execName) {
-		function rw(path) {
-			if (path.endsWith('.worker.js')) {
-				return `${execName}.worker.js`;
-			} else if (path.endsWith('.audio.worklet.js')) {
-				return `${execName}.audio.worklet.js`;
-			} else if (path.endsWith('.js')) {
-				return `${execName}.js`;
-			} else if (path.endsWith('.side.wasm')) {
-				return `${execName}.side.wasm`;
-			} else if (path.endsWith('.wasm')) {
-				return `${execName}.wasm`;
-			}
-			return path;
-		}
-		return rw;
-	},
-
-	createInstantiatePromise: function (wasmLoader) {
-		let loader = wasmLoader;
-		function instantiateWasm(imports, onSuccess) {
-			loader.then(function (xhr) {
-				WebAssembly.instantiate(xhr.response, imports).then(function (result) {
-					onSuccess(result['instance'], result['module']);
-				});
-			});
-			loader = null;
-			return {};
-		}
-
-		return instantiateWasm;
-	},
-
-	findCanvas: function () {
-		const nodes = document.getElementsByTagName('canvas');
-		if (nodes.length && nodes[0] instanceof HTMLCanvasElement) {
-			return nodes[0];
-		}
-		return null;
-	},
-
-	isWebGLAvailable: function (majorVersion = 1) {
-		let testContext = false;
-		try {
-			const testCanvas = document.createElement('canvas');
-			if (majorVersion === 1) {
-				testContext = testCanvas.getContext('webgl') || testCanvas.getContext('experimental-webgl');
-			} else if (majorVersion === 2) {
-				testContext = testCanvas.getContext('webgl2') || testCanvas.getContext('experimental-webgl2');
-			}
-		} catch (e) {
-			// Not available
-		}
-		return !!testContext;
-	},
-};
diff --git a/platform/javascript/js/jsdoc2rst/publish.js b/platform/javascript/js/jsdoc2rst/publish.js
new file mode 100644
index 0000000000..ad9c0fbaaa
--- /dev/null
+++ b/platform/javascript/js/jsdoc2rst/publish.js
@@ -0,0 +1,354 @@
+/* eslint-disable strict */
+
+'use strict';
+
+const fs = require('fs');
+
+class JSDoclet {
+	constructor(doc) {
+		this.doc = doc;
+		this.description = doc['description'] || '';
+		this.name = doc['name'] || 'unknown';
+		this.longname = doc['longname'] || '';
+		this.types = [];
+		if (doc['type'] && doc['type']['names']) {
+			this.types = doc['type']['names'].slice();
+		}
+		this.type = this.types.length > 0 ? this.types.join('\\|') : '*';
+		this.variable = doc['variable'] || false;
+		this.kind = doc['kind'] || '';
+		this.memberof = doc['memberof'] || null;
+		this.scope = doc['scope'] || '';
+		this.members = [];
+		this.optional = doc['optional'] || false;
+		this.defaultvalue = doc['defaultvalue'];
+		this.summary = doc['summary'] || null;
+		this.classdesc = doc['classdesc'] || null;
+
+		// Parameters (functions)
+		this.params = [];
+		this.returns = doc['returns'] ? doc['returns'][0]['type']['names'][0] : 'void';
+		this.returns_desc = doc['returns'] ? doc['returns'][0]['description'] : null;
+
+		this.params = (doc['params'] || []).slice().map((p) => new JSDoclet(p));
+
+		// Custom tags
+		this.tags = doc['tags'] || [];
+		this.header = this.tags.filter((t) => t['title'] === 'header').map((t) => t['text']).pop() || null;
+	}
+
+	add_member(obj) {
+		this.members.push(obj);
+	}
+
+	is_static() {
+		return this.scope === 'static';
+	}
+
+	is_instance() {
+		return this.scope === 'instance';
+	}
+
+	is_object() {
+		return this.kind === 'Object' || (this.kind === 'typedef' && this.type === 'Object');
+	}
+
+	is_class() {
+		return this.kind === 'class';
+	}
+
+	is_function() {
+		return this.kind === 'function' || (this.kind === 'typedef' && this.type === 'function');
+	}
+
+	is_module() {
+		return this.kind === 'module';
+	}
+}
+
+function format_table(f, data, depth = 0) {
+	if (!data.length) {
+		return;
+	}
+
+	const column_sizes = new Array(data[0].length).fill(0);
+
+	data.forEach((row) => {
+		row.forEach((e, idx) => {
+			column_sizes[idx] = Math.max(e.length, column_sizes[idx]);
+		});
+	});
+
+	const indent = ' '.repeat(depth);
+	let sep = indent;
+	column_sizes.forEach((size) => {
+		sep += '+';
+		sep += '-'.repeat(size + 2);
+	});
+	sep += '+\n';
+	f.write(sep);
+
+	data.forEach((row) => {
+		let row_text = `${indent}|`;
+		row.forEach((entry, idx) => {
+			row_text += ` ${entry.padEnd(column_sizes[idx])} |`;
+		});
+		row_text += '\n';
+		f.write(row_text);
+		f.write(sep);
+	});
+
+	f.write('\n');
+}
+
+function make_header(header, sep) {
+	return `${header}\n${sep.repeat(header.length)}\n\n`;
+}
+
+function indent_multiline(text, depth) {
+	const indent = ' '.repeat(depth);
+	return text.split('\n').map((l) => (l === '' ? l : indent + l)).join('\n');
+}
+
+function make_rst_signature(obj, types = false, style = false) {
+	let out = '';
+	const fmt = style ? '*' : '';
+	obj.params.forEach((arg, idx) => {
+		if (idx > 0) {
+			if (arg.optional) {
+				out += ` ${fmt}[`;
+			}
+			out += ', ';
+		} else {
+			out += ' ';
+			if (arg.optional) {
+				out += `${fmt}[ `;
+			}
+		}
+		if (types) {
+			out += `${arg.type} `;
+		}
+		const variable = arg.variable ? '...' : '';
+		const defval = arg.defaultvalue !== undefined ? `=${arg.defaultvalue}` : '';
+		out += `${variable}${arg.name}${defval}`;
+		if (arg.optional) {
+			out += ` ]${fmt}`;
+		}
+	});
+	out += ' ';
+	return out;
+}
+
+function make_rst_param(f, obj, depth = 0) {
+	const indent = ' '.repeat(depth * 3);
+	f.write(indent);
+	f.write(`:param ${obj.type} ${obj.name}:\n`);
+	f.write(indent_multiline(obj.description, (depth + 1) * 3));
+	f.write('\n\n');
+}
+
+function make_rst_attribute(f, obj, depth = 0, brief = false) {
+	const indent = ' '.repeat(depth * 3);
+	f.write(indent);
+	f.write(`.. js:attribute:: ${obj.name}\n\n`);
+
+	if (brief) {
+		if (obj.summary) {
+			f.write(indent_multiline(obj.summary, (depth + 1) * 3));
+		}
+		f.write('\n\n');
+		return;
+	}
+
+	f.write(indent_multiline(obj.description, (depth + 1) * 3));
+	f.write('\n\n');
+
+	f.write(indent);
+	f.write(`   :type: ${obj.type}\n\n`);
+
+	if (obj.defaultvalue !== undefined) {
+		let defval = obj.defaultvalue;
+		if (defval === '') {
+			defval = '""';
+		}
+		f.write(indent);
+		f.write(`   :value: \`\`${defval}\`\`\n\n`);
+	}
+}
+
+function make_rst_function(f, obj, depth = 0) {
+	let prefix = '';
+	if (obj.is_instance()) {
+		prefix = 'prototype.';
+	}
+
+	const indent = ' '.repeat(depth * 3);
+	const sig = make_rst_signature(obj);
+	f.write(indent);
+	f.write(`.. js:function:: ${prefix}${obj.name}(${sig})\n`);
+	f.write('\n');
+
+	f.write(indent_multiline(obj.description, (depth + 1) * 3));
+	f.write('\n\n');
+
+	obj.params.forEach((param) => {
+		make_rst_param(f, param, depth + 1);
+	});
+
+	if (obj.returns !== 'void') {
+		f.write(indent);
+		f.write('   :return:\n');
+		f.write(indent_multiline(obj.returns_desc, (depth + 2) * 3));
+		f.write('\n\n');
+		f.write(indent);
+		f.write(`   :rtype: ${obj.returns}\n\n`);
+	}
+}
+
+function make_rst_object(f, obj) {
+	let brief = false;
+	// Our custom header flag.
+	if (obj.header !== null) {
+		f.write(make_header(obj.header, '-'));
+		f.write(`${obj.description}\n\n`);
+		brief = true;
+	}
+
+	// Format members table and descriptions
+	const data = [['type', 'name']].concat(obj.members.map((m) => [m.type, `:js:attr:\`${m.name}\``]));
+
+	f.write(make_header('Properties', '^'));
+	format_table(f, data, 0);
+
+	make_rst_attribute(f, obj, 0, brief);
+
+	if (!obj.members.length) {
+		return;
+	}
+
+	f.write('   **Property Descriptions**\n\n');
+
+	// Properties first
+	obj.members.filter((m) => !m.is_function()).forEach((m) => {
+		make_rst_attribute(f, m, 1);
+	});
+
+	// Callbacks last
+	obj.members.filter((m) => m.is_function()).forEach((m) => {
+		make_rst_function(f, m, 1);
+	});
+}
+
+function make_rst_class(f, obj) {
+	const header = obj.header ? obj.header : obj.name;
+	f.write(make_header(header, '-'));
+
+	if (obj.classdesc) {
+		f.write(`${obj.classdesc}\n\n`);
+	}
+
+	const funcs = obj.members.filter((m) => m.is_function());
+	function make_data(m) {
+		const base = m.is_static() ? obj.name : `${obj.name}.prototype`;
+		const params = make_rst_signature(m, true, true);
+		const sig = `:js:attr:\`${m.name} <${base}.${m.name}>\` **(**${params}**)**`;
+		return [m.returns, sig];
+	}
+	const sfuncs = funcs.filter((m) => m.is_static());
+	const ifuncs = funcs.filter((m) => !m.is_static());
+
+	f.write(make_header('Static Methods', '^'));
+	format_table(f, sfuncs.map((m) => make_data(m)));
+
+	f.write(make_header('Instance Methods', '^'));
+	format_table(f, ifuncs.map((m) => make_data(m)));
+
+	const sig = make_rst_signature(obj);
+	f.write(`.. js:class:: ${obj.name}(${sig})\n\n`);
+	f.write(indent_multiline(obj.description, 3));
+	f.write('\n\n');
+
+	obj.params.forEach((p) => {
+		make_rst_param(f, p, 1);
+	});
+
+	f.write('   **Static Methods**\n\n');
+	sfuncs.forEach((m) => {
+		make_rst_function(f, m, 1);
+	});
+
+	f.write('   **Instance Methods**\n\n');
+	ifuncs.forEach((m) => {
+		make_rst_function(f, m, 1);
+	});
+}
+
+function make_rst_module(f, obj) {
+	const header = obj.header !== null ? obj.header : obj.name;
+	f.write(make_header(header, '='));
+	f.write(obj.description);
+	f.write('\n\n');
+}
+
+function write_base_object(f, obj) {
+	if (obj.is_object()) {
+		make_rst_object(f, obj);
+	} else if (obj.is_function()) {
+		make_rst_function(f, obj);
+	} else if (obj.is_class()) {
+		make_rst_class(f, obj);
+	} else if (obj.is_module()) {
+		make_rst_module(f, obj);
+	}
+}
+
+function generate(f, docs) {
+	const globs = [];
+	const SYMBOLS = {};
+	docs.filter((d) => !d.ignore && d.kind !== 'package').forEach((d) => {
+		SYMBOLS[d.name] = d;
+		if (d.memberof) {
+			const up = SYMBOLS[d.memberof];
+			if (up === undefined) {
+				console.log(d); // eslint-disable-line no-console
+				console.log(`Undefined symbol! ${d.memberof}`); // eslint-disable-line no-console
+				throw new Error('Undefined symbol!');
+			}
+			SYMBOLS[d.memberof].add_member(d);
+		} else {
+			globs.push(d);
+		}
+	});
+
+	f.write('.. _doc_html5_shell_classref:\n\n');
+	globs.forEach((obj) => write_base_object(f, obj));
+}
+
+/**
+ * Generate documentation output.
+ *
+ * @param {TAFFY} data - A TaffyDB collection representing
+ *                       all the symbols documented in your code.
+ * @param {object} opts - An object with options information.
+ */
+exports.publish = function (data, opts) {
+	const docs = data().get().filter((doc) => !doc.undocumented && !doc.ignore).map((doc) => new JSDoclet(doc));
+	const dest = opts.destination;
+	if (dest === 'dry-run') {
+		process.stdout.write('Dry run... ');
+		generate({
+			write: function () { /* noop */ },
+		}, docs);
+		process.stdout.write('Okay!\n');
+		return;
+	}
+	if (dest !== '' && !dest.endsWith('.rst')) {
+		throw new Error('Destination file must be either a ".rst" file, or an empty string (for printing to stdout)');
+	}
+	if (dest !== '') {
+		const f = fs.createWriteStream(dest);
+		generate(f, docs);
+	} else {
+		generate(process.stdout, docs);
+	}
+};
diff --git a/platform/javascript/js/libs/library_godot_display.js b/platform/javascript/js/libs/library_godot_display.js
index fdb5cc0ec2..c72b6b3691 100644
--- a/platform/javascript/js/libs/library_godot_display.js
+++ b/platform/javascript/js/libs/library_godot_display.js
@@ -671,7 +671,7 @@ const GodotDisplay = {
 			document.head.appendChild(link);
 		}
 		const old_icon = GodotDisplay.window_icon;
-		const png = new Blob([GodotRuntime.heapCopy(HEAPU8, p_ptr, p_len)], { type: 'image/png' });
+		const png = new Blob([GodotRuntime.heapSlice(HEAPU8, p_ptr, p_len)], { type: 'image/png' });
 		GodotDisplay.window_icon = URL.createObjectURL(png);
 		link.href = GodotDisplay.window_icon;
 		if (old_icon) {
@@ -711,7 +711,7 @@ const GodotDisplay = {
 		const shape = GodotRuntime.parseString(p_shape);
 		const old_shape = GodotDisplayCursor.cursors[shape];
 		if (p_len > 0) {
-			const png = new Blob([GodotRuntime.heapCopy(HEAPU8, p_ptr, p_len)], { type: 'image/png' });
+			const png = new Blob([GodotRuntime.heapSlice(HEAPU8, p_ptr, p_len)], { type: 'image/png' });
 			const url = URL.createObjectURL(png);
 			GodotDisplayCursor.cursors[shape] = {
 				url: url,
diff --git a/platform/javascript/js/libs/library_godot_fetch.js b/platform/javascript/js/libs/library_godot_fetch.js
new file mode 100644
index 0000000000..4ae6a23593
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_fetch.js
@@ -0,0 +1,258 @@
+/*************************************************************************/
+/*  library_godot_fetch.js                                               */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+const GodotFetch = {
+	$GodotFetch__deps: ['$GodotRuntime'],
+	$GodotFetch: {
+
+		onread: function (id, result) {
+			const obj = IDHandler.get(id);
+			if (!obj) {
+				return;
+			}
+			if (result.value) {
+				obj.chunks.push(result.value);
+			}
+			obj.reading = false;
+			obj.done = result.done;
+		},
+
+		onresponse: function (id, response) {
+			const obj = IDHandler.get(id);
+			if (!obj) {
+				return;
+			}
+			let size = -1;
+			let compressed = false;
+			let chunked = false;
+			response.headers.forEach(function (value, header) {
+				const v = value.toLowerCase().trim();
+				const h = header.toLowerCase().trim();
+				if (h === 'content-encoding') {
+					compressed = true;
+					size = -1;
+				} else if (h === 'content-length') {
+					const len = Number.parseInt(value, 10);
+					if (!Number.isNaN(len) && !compressed) {
+						size = len;
+					}
+				} else if (h === 'transfer-encoding' && v === 'chunked') {
+					chunked = true;
+				}
+			});
+			obj.bodySize = size;
+			obj.status = response.status;
+			obj.response = response;
+			obj.reader = response.body.getReader();
+			obj.chunked = chunked;
+		},
+
+		onerror: function (id, err) {
+			GodotRuntime.error(err);
+			const obj = IDHandler.get(id);
+			if (!obj) {
+				return;
+			}
+			obj.error = err;
+		},
+
+		create: function (method, url, headers, body) {
+			const obj = {
+				request: null,
+				response: null,
+				reader: null,
+				error: null,
+				done: false,
+				reading: false,
+				status: 0,
+				chunks: [],
+				bodySize: -1,
+			};
+			const id = IDHandler.add(obj);
+			const init = {
+				method: method,
+				headers: headers,
+				body: body,
+			};
+			obj.request = fetch(url, init);
+			obj.request.then(GodotFetch.onresponse.bind(null, id)).catch(GodotFetch.onerror.bind(null, id));
+			return id;
+		},
+
+		free: function (id) {
+			const obj = IDHandler.get(id);
+			if (!obj) {
+				return;
+			}
+			IDHandler.remove(id);
+			if (!obj.request) {
+				return;
+			}
+			// Try to abort
+			obj.request.then(function (response) {
+				response.abort();
+			}).catch(function (e) { /* nothing to do */ });
+		},
+
+		read: function (id) {
+			const obj = IDHandler.get(id);
+			if (!obj) {
+				return;
+			}
+			if (obj.reader && !obj.reading) {
+				if (obj.done) {
+					obj.reader = null;
+					return;
+				}
+				obj.reading = true;
+				obj.reader.read().then(GodotFetch.onread.bind(null, id)).catch(GodotFetch.onerror.bind(null, id));
+			}
+		},
+	},
+
+	godot_js_fetch_create__sig: 'iii',
+	godot_js_fetch_create: function (p_method, p_url, p_headers, p_headers_size, p_body, p_body_size) {
+		const method = GodotRuntime.parseString(p_method);
+		const url = GodotRuntime.parseString(p_url);
+		const headers = GodotRuntime.parseStringArray(p_headers, p_headers_size);
+		const body = p_body_size ? GodotRuntime.heapSlice(HEAP8, p_body, p_body_size) : null;
+		return GodotFetch.create(method, url, headers.map(function (hv) {
+			const idx = hv.indexOf(':');
+			if (idx <= 0) {
+				return [];
+			}
+			return [
+				hv.slice(0, idx).trim(),
+				hv.slice(idx + 1).trim(),
+			];
+		}).filter(function (v) {
+			return v.length === 2;
+		}), body);
+	},
+
+	godot_js_fetch_state_get__sig: 'ii',
+	godot_js_fetch_state_get: function (p_id) {
+		const obj = IDHandler.get(p_id);
+		if (!obj) {
+			return -1;
+		}
+		if (obj.error) {
+			return -1;
+		}
+		if (!obj.response) {
+			return 0;
+		}
+		if (obj.reader) {
+			return 1;
+		}
+		if (obj.done) {
+			return 2;
+		}
+		return -1;
+	},
+
+	godot_js_fetch_http_status_get__sig: 'ii',
+	godot_js_fetch_http_status_get: function (p_id) {
+		const obj = IDHandler.get(p_id);
+		if (!obj || !obj.response) {
+			return 0;
+		}
+		return obj.status;
+	},
+
+	godot_js_fetch_read_headers__sig: 'iii',
+	godot_js_fetch_read_headers: function (p_id, p_parse_cb, p_ref) {
+		const obj = IDHandler.get(p_id);
+		if (!obj || !obj.response) {
+			return 1;
+		}
+		const cb = GodotRuntime.get_func(p_parse_cb);
+		const arr = [];
+		obj.response.headers.forEach(function (v, h) {
+			arr.push(`${h}:${v}`);
+		});
+		const c_ptr = GodotRuntime.allocStringArray(arr);
+		cb(arr.length, c_ptr, p_ref);
+		GodotRuntime.freeStringArray(c_ptr, arr.length);
+		return 0;
+	},
+
+	godot_js_fetch_read_chunk__sig: 'ii',
+	godot_js_fetch_read_chunk: function (p_id, p_buf, p_buf_size) {
+		const obj = IDHandler.get(p_id);
+		if (!obj || !obj.response) {
+			return 0;
+		}
+		let to_read = p_buf_size;
+		const chunks = obj.chunks;
+		while (to_read && chunks.length) {
+			const chunk = obj.chunks[0];
+			if (chunk.length > to_read) {
+				GodotRuntime.heapCopy(HEAP8, chunk.slice(0, to_read), p_buf);
+				chunks[0] = chunk.slice(to_read);
+				to_read = 0;
+			} else {
+				GodotRuntime.heapCopy(HEAP8, chunk, p_buf);
+				to_read -= chunk.length;
+				chunks.pop();
+			}
+		}
+		if (!chunks.length) {
+			GodotFetch.read(p_id);
+		}
+		return p_buf_size - to_read;
+	},
+
+	godot_js_fetch_body_length_get__sig: 'ii',
+	godot_js_fetch_body_length_get: function (p_id) {
+		const obj = IDHandler.get(p_id);
+		if (!obj || !obj.response) {
+			return -1;
+		}
+		return obj.bodySize;
+	},
+
+	godot_js_fetch_is_chunked__sig: 'ii',
+	godot_js_fetch_is_chunked: function (p_id) {
+		const obj = IDHandler.get(p_id);
+		if (!obj || !obj.response) {
+			return -1;
+		}
+		return obj.chunked ? 1 : 0;
+	},
+
+	godot_js_fetch_free__sig: 'vi',
+	godot_js_fetch_free: function (id) {
+		GodotFetch.free(id);
+	},
+};
+
+autoAddDeps(GodotFetch, '$GodotFetch');
+mergeInto(LibraryManager.library, GodotFetch);
diff --git a/platform/javascript/js/libs/library_godot_http_request.js b/platform/javascript/js/libs/library_godot_http_request.js
deleted file mode 100644
index 7dc2a2df29..0000000000
--- a/platform/javascript/js/libs/library_godot_http_request.js
+++ /dev/null
@@ -1,142 +0,0 @@
-/*************************************************************************/
-/*  http_request.js                                                      */
-/*************************************************************************/
-/*                       This file is part of:                           */
-/*                           GODOT ENGINE                                */
-/*                      https://godotengine.org                          */
-/*************************************************************************/
-/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
-/*                                                                       */
-/* Permission is hereby granted, free of charge, to any person obtaining */
-/* a copy of this software and associated documentation files (the       */
-/* "Software"), to deal in the Software without restriction, including   */
-/* without limitation the rights to use, copy, modify, merge, publish,   */
-/* distribute, sublicense, and/or sell copies of the Software, and to    */
-/* permit persons to whom the Software is furnished to do so, subject to */
-/* the following conditions:                                             */
-/*                                                                       */
-/* The above copyright notice and this permission notice shall be        */
-/* included in all copies or substantial portions of the Software.       */
-/*                                                                       */
-/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
-/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
-/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
-/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
-/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
-/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
-/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
-/*************************************************************************/
-
-const GodotHTTPRequest = {
-	$GodotHTTPRequest__deps: ['$GodotRuntime'],
-	$GodotHTTPRequest: {
-		requests: [],
-
-		getUnusedRequestId: function () {
-			const idMax = GodotHTTPRequest.requests.length;
-			for (let potentialId = 0; potentialId < idMax; ++potentialId) {
-				if (GodotHTTPRequest.requests[potentialId] instanceof XMLHttpRequest) {
-					continue;
-				}
-				return potentialId;
-			}
-			GodotHTTPRequest.requests.push(null);
-			return idMax;
-		},
-
-		setupRequest: function (xhr) {
-			xhr.responseType = 'arraybuffer';
-		},
-	},
-
-	godot_xhr_new__sig: 'i',
-	godot_xhr_new: function () {
-		const newId = GodotHTTPRequest.getUnusedRequestId();
-		GodotHTTPRequest.requests[newId] = new XMLHttpRequest();
-		GodotHTTPRequest.setupRequest(GodotHTTPRequest.requests[newId]);
-		return newId;
-	},
-
-	godot_xhr_reset__sig: 'vi',
-	godot_xhr_reset: function (xhrId) {
-		GodotHTTPRequest.requests[xhrId] = new XMLHttpRequest();
-		GodotHTTPRequest.setupRequest(GodotHTTPRequest.requests[xhrId]);
-	},
-
-	godot_xhr_free__sig: 'vi',
-	godot_xhr_free: function (xhrId) {
-		GodotHTTPRequest.requests[xhrId].abort();
-		GodotHTTPRequest.requests[xhrId] = null;
-	},
-
-	godot_xhr_open__sig: 'viiiii',
-	godot_xhr_open: function (xhrId, method, url, p_user, p_password) {
-		const user = p_user > 0 ? GodotRuntime.parseString(p_user) : null;
-		const password = p_password > 0 ? GodotRuntime.parseString(p_password) : null;
-		GodotHTTPRequest.requests[xhrId].open(GodotRuntime.parseString(method), GodotRuntime.parseString(url), true, user, password);
-	},
-
-	godot_xhr_set_request_header__sig: 'viii',
-	godot_xhr_set_request_header: function (xhrId, header, value) {
-		GodotHTTPRequest.requests[xhrId].setRequestHeader(GodotRuntime.parseString(header), GodotRuntime.parseString(value));
-	},
-
-	godot_xhr_send__sig: 'viii',
-	godot_xhr_send: function (xhrId, p_ptr, p_len) {
-		let data = null;
-		if (p_ptr && p_len) {
-			data = GodotRuntime.heapCopy(HEAP8, p_ptr, p_len);
-		}
-		GodotHTTPRequest.requests[xhrId].send(data);
-	},
-
-	godot_xhr_abort__sig: 'vi',
-	godot_xhr_abort: function (xhrId) {
-		GodotHTTPRequest.requests[xhrId].abort();
-	},
-
-	godot_xhr_get_status__sig: 'ii',
-	godot_xhr_get_status: function (xhrId) {
-		return GodotHTTPRequest.requests[xhrId].status;
-	},
-
-	godot_xhr_get_ready_state__sig: 'ii',
-	godot_xhr_get_ready_state: function (xhrId) {
-		return GodotHTTPRequest.requests[xhrId].readyState;
-	},
-
-	godot_xhr_get_response_headers_length__sig: 'ii',
-	godot_xhr_get_response_headers_length: function (xhrId) {
-		const headers = GodotHTTPRequest.requests[xhrId].getAllResponseHeaders();
-		return headers === null ? 0 : GodotRuntime.strlen(headers);
-	},
-
-	godot_xhr_get_response_headers__sig: 'viii',
-	godot_xhr_get_response_headers: function (xhrId, dst, len) {
-		const str = GodotHTTPRequest.requests[xhrId].getAllResponseHeaders();
-		if (str === null) {
-			return;
-		}
-		GodotRuntime.stringToHeap(str, dst, len);
-	},
-
-	godot_xhr_get_response_length__sig: 'ii',
-	godot_xhr_get_response_length: function (xhrId) {
-		const body = GodotHTTPRequest.requests[xhrId].response;
-		return body === null ? 0 : body.byteLength;
-	},
-
-	godot_xhr_get_response__sig: 'viii',
-	godot_xhr_get_response: function (xhrId, dst, len) {
-		let buf = GodotHTTPRequest.requests[xhrId].response;
-		if (buf === null) {
-			return;
-		}
-		buf = new Uint8Array(buf).subarray(0, len);
-		HEAPU8.set(buf, dst);
-	},
-};
-
-autoAddDeps(GodotHTTPRequest, '$GodotHTTPRequest');
-mergeInto(LibraryManager.library, GodotHTTPRequest);
diff --git a/platform/javascript/js/libs/library_godot_runtime.js b/platform/javascript/js/libs/library_godot_runtime.js
index 7e36ff8ab5..3da1ed8f06 100644
--- a/platform/javascript/js/libs/library_godot_runtime.js
+++ b/platform/javascript/js/libs/library_godot_runtime.js
@@ -72,11 +72,16 @@ const GodotRuntime = {
 			return p_heap.subarray(p_ptr / bytes, p_ptr / bytes + p_len);
 		},
 
-		heapCopy: function (p_heap, p_ptr, p_len) {
+		heapSlice: function (p_heap, p_ptr, p_len) {
 			const bytes = p_heap.BYTES_PER_ELEMENT;
 			return p_heap.slice(p_ptr / bytes, p_ptr / bytes + p_len);
 		},
 
+		heapCopy: function (p_dst, p_src, p_ptr) {
+			const bytes = p_src.BYTES_PER_ELEMENT;
+			return p_dst.set(p_src, p_ptr / bytes);
+		},
+
 		/*
 		 * Strings
 		 */
@@ -84,6 +89,15 @@ const GodotRuntime = {
 			return UTF8ToString(p_ptr); // eslint-disable-line no-undef
 		},
 
+		parseStringArray: function (p_ptr, p_size) {
+			const strings = [];
+			const ptrs = GodotRuntime.heapSub(HEAP32, p_ptr, p_size); // TODO wasm64
+			ptrs.forEach(function (ptr) {
+				strings.push(GodotRuntime.parseString(ptr));
+			});
+			return strings;
+		},
+
 		strlen: function (p_str) {
 			return lengthBytesUTF8(p_str); // eslint-disable-line no-undef
 		},