[HTML5] Libraries refactor for linting.

Initial work to make liniting easier.

This includes:
- Rename http_request.js to library_godot_http_request.js.
- Rename externs.js to engine.externs.js.
- New library_godot_runtime.js (GodotRuntime) wraps around emscripten
  functions.
- Refactor of XMLHttpRequest handler in engine/preloader.js.
- Few fixes to bugs spotted by early stage linting.

12 files changed, 2156 insertions, 0 deletions

diff --git a/platform/javascript/js/engine/engine.externs.js b/platform/javascript/js/engine/engine.externs.js
new file mode 100644
index 0000000000..1a94dd15ec
--- /dev/null
+++ b/platform/javascript/js/engine/engine.externs.js
@@ -0,0 +1,3 @@
+var Godot;
+var WebAssembly = {};
+WebAssembly.instantiate = function(buffer, imports) {};
diff --git a/platform/javascript/js/engine/engine.js b/platform/javascript/js/engine/engine.js
new file mode 100644
index 0000000000..792ec9cb28
--- /dev/null
+++ b/platform/javascript/js/engine/engine.js
@@ -0,0 +1,278 @@
+const Engine = (function() {
+	var preloader = new Preloader();
+
+	var wasmExt = '.wasm';
+	var unloadAfterInit = true;
+	var loadPath = '';
+	var loadPromise = null;
+	var initPromise = null;
+	var stderr = null;
+	var stdout = null;
+	var progressFunc = null;
+
+	function load(basePath) {
+		if (loadPromise == null) {
+			loadPath = basePath;
+			loadPromise = preloader.loadPromise(basePath + wasmExt);
+			preloader.setProgressFunc(progressFunc);
+			requestAnimationFrame(preloader.animateProgress);
+		}
+		return loadPromise;
+	};
+
+	function unload() {
+		loadPromise = null;
+	};
+
+	/** @constructor */
+	function Engine() { // eslint-disable-line no-shadow
+		this.canvas = null;
+		this.executableName = '';
+		this.rtenv = null;
+		this.customLocale = null;
+		this.resizeCanvasOnStart = false;
+		this.onExecute = null;
+		this.onExit = null;
+		this.persistentPaths = ['/userfs'];
+	};
+
+	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."));
+				return initPromise;
+			}
+			load(basePath);
+		}
+		var config = {};
+		if (typeof stdout === 'function')
+			config.print = stdout;
+		if (typeof stderr === 'function')
+			config.printErr = stderr;
+		var me = this;
+		initPromise = new Promise(function(resolve, reject) {
+			config['locateFile'] = Utils.createLocateRewrite(loadPath);
+			config['instantiateWasm'] = Utils.createInstantiatePromise(loadPromise);
+			Godot(config).then(function(module) {
+				module['initFS'](me.persistentPaths).then(function(fs_err) {
+					me.rtenv = module;
+					if (unloadAfterInit) {
+						unload();
+					}
+					resolve();
+					config = null;
+				});
+			});
+		});
+		return initPromise;
+	};
+
+	/** @type {function(string, string):Object} */
+	Engine.prototype.preloadFile = function(file, path) {
+		return preloader.preload(file, path);
+	};
+
+	/** @type {function(...string):Object} */
+	Engine.prototype.start = function() {
+		// Start from arguments.
+		var args = [];
+		for (var i = 0; i < arguments.length; i++) {
+			args.push(arguments[i]);
+		}
+		var 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'));
+			}
+
+			if (!(me.canvas instanceof HTMLCanvasElement)) {
+				me.canvas = Utils.findCanvas();
+				if (!me.canvas) {
+					return Promise.reject(new Error('No canvas found in page'));
+				}
+			}
+
+			// Canvas can grab focus on click, or key events won't work.
+			if (me.canvas.tabIndex < 0) {
+				me.canvas.tabIndex = 0;
+			}
+
+			// Disable right-click context menu.
+			me.canvas.addEventListener('contextmenu', function(ev) {
+				ev.preventDefault();
+			}, false);
+
+			// Until context restoration is implemented warn the user of context loss.
+			me.canvas.addEventListener('webglcontextlost', function(ev) {
+				alert("WebGL context lost, please reload the page"); // eslint-disable-line no-alert
+				ev.preventDefault();
+			}, false);
+
+			// Browser locale, or custom one if defined.
+			var locale = me.customLocale;
+			if (!locale) {
+				locale = navigator.languages ? navigator.languages[0] : navigator.language;
+				locale = locale.split('.')[0];
+			}
+			// Emscripten configuration.
+			me.rtenv['thisProgram'] = me.executableName;
+			me.rtenv['noExitRuntime'] = true;
+			// Godot configuration.
+			me.rtenv['initConfig']({
+				'resizeCanvasOnStart': me.resizeCanvasOnStart,
+				'canvas': me.canvas,
+				'locale': locale,
+				'onExecute': function(p_args) {
+					if (me.onExecute) {
+						me.onExecute(p_args);
+						return 0;
+					}
+					return 1;
+				},
+				'onExit': function(p_code) {
+					me.rtenv['deinitFS']();
+					if (me.onExit) {
+						me.onExit(p_code);
+					}
+					me.rtenv = null;
+				},
+			});
+
+			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'](args);
+				initPromise = null;
+				resolve();
+			});
+		});
+	};
+
+	Engine.prototype.startGame = function(execName, mainPack, extraArgs) {
+		// Start and init with execName as loadPath if not inited.
+		this.executableName = execName;
+		var me = this;
+		return Promise.all([
+			this.init(execName),
+			this.preloadFile(mainPack, mainPack)
+		]).then(function() {
+			var args = ['--main-pack', mainPack];
+			if (extraArgs)
+				args = args.concat(extraArgs);
+			return me.start.apply(me, args);
+		});
+	};
+
+	Engine.prototype.setWebAssemblyFilenameExtension = function(override) {
+		if (String(override).length === 0) {
+			throw new Error('Invalid WebAssembly filename extension override');
+		}
+		wasmExt = String(override);
+	};
+
+	Engine.prototype.setUnloadAfterInit = function(enabled) {
+		unloadAfterInit = enabled;
+	};
+
+	Engine.prototype.setCanvas = function(canvasElem) {
+		this.canvas = canvasElem;
+	};
+
+	Engine.prototype.setCanvasResizedOnStart = function(enabled) {
+		this.resizeCanvasOnStart = enabled;
+	};
+
+	Engine.prototype.setLocale = function(locale) {
+		this.customLocale = locale;
+	};
+
+	Engine.prototype.setExecutableName = function(newName) {
+		this.executableName = newName;
+	};
+
+	Engine.prototype.setProgressFunc = function(func) {
+		progressFunc = func;
+	};
+
+	Engine.prototype.setStdoutFunc = function(func) {
+		var print = function(text) {
+			let msg = text;
+			if (arguments.length > 1) {
+				msg = Array.prototype.slice.call(arguments).join(" ");
+			}
+			func(msg);
+		};
+		if (this.rtenv)
+			this.rtenv.print = print;
+		stdout = print;
+	};
+
+	Engine.prototype.setStderrFunc = function(func) {
+		var printErr = function(text) {
+			let msg = text
+			if (arguments.length > 1) {
+				msg = Array.prototype.slice.call(arguments).join(" ");
+			}
+			func(msg);
+		};
+		if (this.rtenv)
+			this.rtenv.printErr = printErr;
+		stderr = printErr;
+	};
+
+	Engine.prototype.setOnExecute = function(onExecute) {
+		this.onExecute = onExecute;
+	};
+
+	Engine.prototype.setOnExit = function(onExit) {
+		this.onExit = onExit;
+	};
+
+	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);
+	};
+
+	Engine.prototype.setPersistentPaths = function(persistentPaths) {
+		this.persistentPaths = persistentPaths;
+	};
+
+	Engine.prototype.requestQuit = function() {
+		if (this.rtenv) {
+			this.rtenv['request_quit']();
+		}
+	};
+
+	// 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['setWebAssemblyFilenameExtension'] = Engine.prototype.setWebAssemblyFilenameExtension;
+	Engine.prototype['setUnloadAfterInit'] = Engine.prototype.setUnloadAfterInit;
+	Engine.prototype['setCanvas'] = Engine.prototype.setCanvas;
+	Engine.prototype['setCanvasResizedOnStart'] = Engine.prototype.setCanvasResizedOnStart;
+	Engine.prototype['setLocale'] = Engine.prototype.setLocale;
+	Engine.prototype['setExecutableName'] = Engine.prototype.setExecutableName;
+	Engine.prototype['setProgressFunc'] = Engine.prototype.setProgressFunc;
+	Engine.prototype['setStdoutFunc'] = Engine.prototype.setStdoutFunc;
+	Engine.prototype['setStderrFunc'] = Engine.prototype.setStderrFunc;
+	Engine.prototype['setOnExecute'] = Engine.prototype.setOnExecute;
+	Engine.prototype['setOnExit'] = Engine.prototype.setOnExit;
+	Engine.prototype['copyToFS'] = Engine.prototype.copyToFS;
+	Engine.prototype['setPersistentPaths'] = Engine.prototype.setPersistentPaths;
+	Engine.prototype['requestQuit'] = Engine.prototype.requestQuit;
+	return Engine;
+})();
+if (typeof window !== 'undefined') window['Engine'] = Engine;
diff --git a/platform/javascript/js/engine/preloader.js b/platform/javascript/js/engine/preloader.js
new file mode 100644
index 0000000000..8641646e6e
--- /dev/null
+++ b/platform/javascript/js/engine/preloader.js
@@ -0,0 +1,129 @@
+var Preloader = /** @constructor */ function() { // eslint-disable-line no-unused-vars
+
+	const loadXHR = function(resolve, reject, file, tracker, attempts) {
+		const xhr = new XMLHttpRequest();
+		tracker[file] = {
+			total: 0,
+			loaded: 0,
+			final: false,
+		};
+		xhr.onerror = function() {
+			if (attempts <= 1) {
+				reject(new Error("Failed loading file '" + file + "'"));
+			} else {
+				setTimeout(function () {
+					loadXHR(resolve, reject, file, tracker, attempts - 1);
+				}, 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();
+	};
+
+	const DOWNLOAD_ATTEMPTS_MAX = 4;
+	const loadingFiles = {};
+	const lastProgress = { loaded: 0, total: 0 };
+	let progressFunc = null;
+
+	const animateProgress = function() {
+
+		var loaded = 0;
+		var total = 0;
+		var totalIsValid = true;
+		var progressIsFinal = true;
+
+		Object.keys(loadingFiles).forEach(function(file) {
+			const stat = loadingFiles[file];
+			if (!stat.final) {
+				progressIsFinal = false;
+			}
+			if (!totalIsValid || stat.total === 0) {
+				totalIsValid = false;
+				total = 0;
+			} else {
+				total += stat.total;
+			}
+			loaded += stat.loaded;
+		});
+		if (loaded !== lastProgress.loaded || total !== lastProgress.total) {
+			lastProgress.loaded = loaded;
+			lastProgress.total = total;
+			if (typeof progressFunc === 'function')
+				progressFunc(loaded, total);
+		}
+		if (!progressIsFinal)
+			requestAnimationFrame(animateProgress);
+	}
+
+	this.animateProgress = animateProgress;
+
+	this.setProgressFunc = function(callback) {
+		progressFunc = callback;
+	}
+
+
+	this.loadPromise = function(file) {
+		return new Promise(function(resolve, reject) {
+			loadXHR(resolve, reject, file, loadingFiles, DOWNLOAD_ATTEMPTS_MAX);
+		});
+	}
+
+	this.preloadedFiles = [];
+	this.preload = function(pathOrBuffer, destPath) {
+		let buffer = null;
+		if (typeof pathOrBuffer === 'string') {
+			var me = this;
+			return this.loadPromise(pathOrBuffer).then(function(xhr) {
+				me.preloadedFiles.push({
+					path: destPath || pathOrBuffer,
+					buffer: xhr.response
+				});
+				return Promise.resolve();
+			});
+		} else if (pathOrBuffer instanceof ArrayBuffer) {
+			buffer = new Uint8Array(pathOrBuffer);
+		} else if (ArrayBuffer.isView(pathOrBuffer)) {
+			buffer = new Uint8Array(pathOrBuffer.buffer);
+		}
+		if (buffer) {
+			this.preloadedFiles.push({
+				path: destPath,
+				buffer: pathOrBuffer
+			});
+			return Promise.resolve();
+		} else {
+			return Promise.reject(new Error("Invalid object for preloading"));
+		}
+	};
+};
diff --git a/platform/javascript/js/engine/utils.js b/platform/javascript/js/engine/utils.js
new file mode 100644
index 0000000000..fbab9ba9f9
--- /dev/null
+++ b/platform/javascript/js/engine/utils.js
@@ -0,0 +1,57 @@
+var 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('.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() {
+		var nodes = document.getElementsByTagName('canvas');
+		if (nodes.length && nodes[0] instanceof HTMLCanvasElement) {
+			return nodes[0];
+		}
+		return null;
+	},
+
+	isWebGLAvailable: function(majorVersion = 1) {
+
+		var testContext = false;
+		try {
+			var 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/libs/audio.worklet.js b/platform/javascript/js/libs/audio.worklet.js
new file mode 100644
index 0000000000..a27035ef22
--- /dev/null
+++ b/platform/javascript/js/libs/audio.worklet.js
@@ -0,0 +1,186 @@
+/*************************************************************************/
+/*  audio.worklet.js                                                     */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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.                */
+/*************************************************************************/
+
+class RingBuffer {
+	constructor(p_buffer, p_state) {
+		this.buffer = p_buffer;
+		this.avail = p_state;
+		this.rpos = 0;
+		this.wpos = 0;
+	}
+
+	data_left() {
+		return Atomics.load(this.avail, 0);
+	}
+
+	space_left() {
+		return this.buffer.length - this.data_left();
+	}
+
+	read(output) {
+		const size = this.buffer.length;
+		let from = 0;
+		let to_write = output.length;
+		if (this.rpos + to_write > size) {
+			const high = size - this.rpos;
+			output.set(this.buffer.subarray(this.rpos, size));
+			from = high;
+			to_write -= high;
+			this.rpos = 0;
+		}
+		output.set(this.buffer.subarray(this.rpos, this.rpos + to_write), from);
+		this.rpos += to_write;
+		Atomics.add(this.avail, 0, -output.length);
+		Atomics.notify(this.avail, 0);
+	}
+
+	write(p_buffer) {
+		const to_write = p_buffer.length;
+		const mw = this.buffer.length - this.wpos;
+		if (mw >= to_write) {
+			this.buffer.set(p_buffer, this.wpos);
+		} else {
+			const high = p_buffer.subarray(0, to_write - mw);
+			const low = p_buffer.subarray(to_write - mw);
+			this.buffer.set(high, this.wpos);
+			this.buffer.set(low);
+		}
+		let diff = to_write;
+		if (this.wpos + diff >= this.buffer.length) {
+			diff -= this.buffer.length;
+		}
+		this.wpos += diff;
+		Atomics.add(this.avail, 0, to_write);
+		Atomics.notify(this.avail, 0);
+	}
+}
+
+class GodotProcessor extends AudioWorkletProcessor {
+	constructor() {
+		super();
+		this.running = true;
+		this.lock = null;
+		this.notifier = null;
+		this.output = null;
+		this.output_buffer = new Float32Array();
+		this.input = null;
+		this.input_buffer = new Float32Array();
+		this.port.onmessage = (event) => {
+			const cmd = event.data['cmd'];
+			const data = event.data['data'];
+			this.parse_message(cmd, data);
+		};
+	}
+
+	process_notify() {
+		Atomics.add(this.notifier, 0, 1);
+		Atomics.notify(this.notifier, 0);
+	}
+
+	parse_message(p_cmd, p_data) {
+		if (p_cmd === "start" && p_data) {
+			const state = p_data[0];
+			let idx = 0;
+			this.lock = state.subarray(idx, ++idx);
+			this.notifier = state.subarray(idx, ++idx);
+			const avail_in = state.subarray(idx, ++idx);
+			const avail_out = state.subarray(idx, ++idx);
+			this.input = new RingBuffer(p_data[1], avail_in);
+			this.output = new RingBuffer(p_data[2], avail_out);
+		} else if (p_cmd === "stop") {
+			this.runing = false;
+			this.output = null;
+			this.input = null;
+		}
+	}
+
+	static array_has_data(arr) {
+		return arr.length && arr[0].length && arr[0][0].length;
+	}
+
+	process(inputs, outputs, parameters) {
+		if (!this.running) {
+			return false; // Stop processing.
+		}
+		if (this.output === null) {
+			return true; // Not ready yet, keep processing.
+		}
+		const process_input = GodotProcessor.array_has_data(inputs);
+		if (process_input) {
+			const input = inputs[0];
+			const chunk = input[0].length * input.length;
+			if (this.input_buffer.length !== chunk) {
+				this.input_buffer = new Float32Array(chunk);
+			}
+			if (this.input.space_left() >= chunk) {
+				GodotProcessor.write_input(this.input_buffer, input);
+				this.input.write(this.input_buffer);
+			} else {
+				this.port.postMessage("Input buffer is full! Skipping input frame.");
+			}
+		}
+		const process_output = GodotProcessor.array_has_data(outputs);
+		if (process_output) {
+			const output = outputs[0];
+			const chunk = output[0].length * output.length;
+			if (this.output_buffer.length !== chunk) {
+				this.output_buffer = new Float32Array(chunk);
+			}
+			if (this.output.data_left() >= chunk) {
+				this.output.read(this.output_buffer);
+				GodotProcessor.write_output(output, this.output_buffer);
+			} else {
+				this.port.postMessage("Output buffer has not enough frames! Skipping output frame.");
+			}
+		}
+		this.process_notify();
+		return true;
+	}
+
+	static write_output(dest, source) {
+		const channels = dest.length;
+		for (let ch = 0; ch < channels; ch++) {
+			for (let sample = 0; sample < dest[ch].length; sample++) {
+				dest[ch][sample] = source[sample * channels + ch];
+			}
+		}
+	}
+
+	static write_input(dest, source) {
+		const channels = source.length;
+		for (let ch = 0; ch < channels; ch++) {
+			for (let sample = 0; sample < source[ch].length; sample++) {
+				dest[sample * channels + ch] = source[ch][sample];
+			}
+		}
+	}
+}
+
+registerProcessor('godot-processor', GodotProcessor);
diff --git a/platform/javascript/js/libs/library_godot_audio.js b/platform/javascript/js/libs/library_godot_audio.js
new file mode 100644
index 0000000000..a657d0a125
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_audio.js
@@ -0,0 +1,340 @@
+/*************************************************************************/
+/*  library_godot_audio.js                                               */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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 GodotAudio = {
+	$GodotAudio__deps: ['$GodotRuntime', '$GodotOS'],
+	$GodotAudio: {
+		ctx: null,
+		input: null,
+		driver: null,
+		interval: 0,
+
+		init: function(mix_rate, latency, onstatechange, onlatencyupdate) {
+			const ctx = new (window.AudioContext || window.webkitAudioContext)({
+				sampleRate: mix_rate,
+				// latencyHint: latency / 1000 // Do not specify, leave 'interactive' for good performance.
+			});
+			GodotAudio.ctx = ctx;
+			ctx.onstatechange = function() {
+				let state = 0;
+				switch (ctx.state) {
+					case 'suspended':
+						state = 0;
+						break;
+					case 'running':
+						state = 1;
+						break;
+					case 'closed':
+						state = 2;
+						break;
+
+					// no default
+				}
+				onstatechange(state);
+			}
+			ctx.onstatechange(); // Immeditately notify state.
+			// Update computed latency
+			GodotAudio.interval = setInterval(function() {
+				let computed_latency = 0;
+				if (ctx.baseLatency) {
+					computed_latency += GodotAudio.ctx.baseLatency;
+				}
+				if (ctx.outputLatency) {
+					computed_latency += GodotAudio.ctx.outputLatency;
+				}
+				onlatencyupdate(computed_latency);
+			}, 1000);
+			GodotOS.atexit(GodotAudio.close_async);
+			return ctx.destination.channelCount;
+		},
+
+		create_input: function(callback) {
+			if (GodotAudio.input) {
+				return; // Already started.
+			}
+			function gotMediaInput(stream) {
+				GodotAudio.input = GodotAudio.ctx.createMediaStreamSource(stream);
+				callback(GodotAudio.input)
+			}
+			if (navigator.mediaDevices.getUserMedia) {
+				navigator.mediaDevices.getUserMedia({
+					"audio": true
+				}).then(gotMediaInput, function(e) { GodotRuntime.print(e) });
+			} else {
+				if (!navigator.getUserMedia) {
+					navigator.getUserMedia = navigator.webkitGetUserMedia || navigator.mozGetUserMedia;
+				}
+				navigator.getUserMedia({
+					"audio": true
+				}, gotMediaInput, function(e) { GodotRuntime.print(e) });
+			}
+		},
+
+		close_async: function(resolve, reject) {
+			const ctx = GodotAudio.ctx;
+			GodotAudio.ctx = null;
+			// Audio was not initialized.
+			if (!ctx) {
+				resolve();
+				return;
+			}
+			// Remove latency callback
+			if (GodotAudio.interval) {
+				clearInterval(GodotAudio.interval);
+				GodotAudio.interval = 0;
+			}
+			// Disconnect input, if it was started.
+			if (GodotAudio.input) {
+				GodotAudio.input.disconnect();
+				GodotAudio.input = null;
+			}
+			// Disconnect output
+			let closed = Promise.resolve();
+			if (GodotAudio.driver) {
+				closed = GodotAudio.driver.close();
+			}
+			closed.then(function() {
+				return ctx.close();
+			}).then(function() {
+				ctx.onstatechange = null;
+				resolve();
+			}).catch(function(e) {
+				ctx.onstatechange = null;
+				GodotRuntime.error("Error closing AudioContext", e);
+				resolve();
+			});
+		},
+	},
+
+	godot_audio_is_available__proxy: 'sync',
+	godot_audio_is_available: function () {
+		if (!(window.AudioContext || window.webkitAudioContext)) {
+			return 0;
+		}
+		return 1;
+	},
+
+	godot_audio_init: function(p_mix_rate, p_latency, p_state_change, p_latency_update) {
+		const statechange = GodotRuntime.get_func(p_state_change);
+		const latencyupdate = GodotRuntime.get_func(p_latency_update);
+		return GodotAudio.init(p_mix_rate, p_latency, statechange, latencyupdate);
+	},
+
+	godot_audio_resume: function() {
+		if (GodotAudio.ctx && GodotAudio.ctx.state !== 'running') {
+			GodotAudio.ctx.resume();
+		}
+	},
+
+	godot_audio_capture_start__proxy: 'sync',
+	godot_audio_capture_start: function() {
+		if (GodotAudio.input) {
+			return; // Already started.
+		}
+		GodotAudio.create_input(function(input) {
+			input.connect(GodotAudio.driver.get_node());
+		});
+	},
+
+	godot_audio_capture_stop__proxy: 'sync',
+	godot_audio_capture_stop: function() {
+		if (GodotAudio.input) {
+			const tracks = GodotAudio.input['mediaStream']['getTracks']();
+			for (let i = 0; i < tracks.length; i++) {
+				tracks[i]['stop']();
+			}
+			GodotAudio.input.disconnect();
+			GodotAudio.input = null;
+		}
+	},
+};
+
+autoAddDeps(GodotAudio, "$GodotAudio");
+mergeInto(LibraryManager.library, GodotAudio);
+
+/**
+ * The AudioWorklet API driver, used when threads are available.
+ */
+const GodotAudioWorklet = {
+	$GodotAudioWorklet__deps: ['$GodotAudio', '$GodotConfig'],
+	$GodotAudioWorklet: {
+		promise: null,
+		worklet: null,
+
+		create: function(channels) {
+			const path = GodotConfig.locate_file('godot.audio.worklet.js');
+			GodotAudioWorklet.promise = GodotAudio.ctx.audioWorklet.addModule(path).then(function() {
+				GodotAudioWorklet.worklet = new AudioWorkletNode(
+					GodotAudio.ctx,
+					'godot-processor',
+					{
+						'outputChannelCount': [channels]
+					}
+				);
+				return Promise.resolve();
+			});
+			GodotAudio.driver = GodotAudioWorklet;
+		},
+
+		start: function(in_buf, out_buf, state) {
+			GodotAudioWorklet.promise.then(function() {
+				const node = GodotAudioWorklet.worklet;
+				node.connect(GodotAudio.ctx.destination);
+				node.port.postMessage({
+					'cmd': 'start',
+					'data': [state, in_buf, out_buf],
+				});
+				node.port.onmessage = function(event) {
+					GodotRuntime.error(event.data);
+				};
+			});
+		},
+
+		get_node: function() {
+			return GodotAudioWorklet.worklet;
+		},
+
+		close: function() {
+			return new Promise(function(resolve, reject) {
+				GodotAudioWorklet.promise.then(function() {
+					GodotAudioWorklet.worklet.port.postMessage({
+						'cmd': 'stop',
+						'data': null,
+					});
+					GodotAudioWorklet.worklet.disconnect();
+					GodotAudioWorklet.worklet = null;
+					GodotAudioWorklet.promise = null;
+					resolve();
+				});
+			});
+		},
+	},
+
+	godot_audio_worklet_create: function(channels) {
+		GodotAudioWorklet.create(channels);
+	},
+
+	godot_audio_worklet_start: function(p_in_buf, p_in_size, p_out_buf, p_out_size, p_state) {
+		const out_buffer = GodotRuntime.heapSub(HEAPF32, p_out_buf, p_out_size);
+		const in_buffer = GodotRuntime.heapSub(HEAPF32, p_in_buf, p_in_size);
+		const state = GodotRuntime.heapSub(HEAP32, p_state, 4);
+		GodotAudioWorklet.start(in_buffer, out_buffer, state);
+	},
+
+	godot_audio_worklet_state_wait: function(p_state, p_idx, p_expected, p_timeout) {
+		Atomics.wait(HEAP32, (p_state >> 2) + p_idx, p_expected, p_timeout);
+		return Atomics.load(HEAP32, (p_state >> 2) + p_idx);
+	},
+
+	godot_audio_worklet_state_add: function(p_state, p_idx, p_value) {
+		return Atomics.add(HEAP32, (p_state >> 2) + p_idx, p_value);
+	},
+
+	godot_audio_worklet_state_get: function(p_state, p_idx) {
+		return Atomics.load(HEAP32, (p_state >> 2) + p_idx);
+	},
+};
+
+autoAddDeps(GodotAudioWorklet, "$GodotAudioWorklet");
+mergeInto(LibraryManager.library, GodotAudioWorklet);
+
+/*
+ * The deprecated ScriptProcessorNode API, used when threads are disabled.
+ */
+const GodotAudioScript = {
+	$GodotAudioScript__deps: ['$GodotAudio'],
+	$GodotAudioScript: {
+		script: null,
+
+		create: function(buffer_length, channel_count) {
+			GodotAudioScript.script = GodotAudio.ctx.createScriptProcessor(buffer_length, 2, channel_count);
+			GodotAudio.driver = GodotAudioScript;
+			return GodotAudioScript.script.bufferSize;
+		},
+
+		start: function(p_in_buf, p_in_size, p_out_buf, p_out_size, onprocess) {
+			GodotAudioScript.script.onaudioprocess = function(event) {
+				// Read input
+				const inb = GodotRuntime.heapSub(HEAPF32, p_in_buf, p_in_size);
+				const input = event.inputBuffer;
+				if (GodotAudio.input) {
+					const inlen = input.getChannelData(0).length;
+					for (let ch = 0; ch < 2; ch++) {
+						const data = input.getChannelData(ch);
+						for (let s = 0; s < inlen; s++) {
+							inb[s * 2 + ch] = data[s];
+						}
+					}
+				}
+
+				// Let Godot process the input/output.
+				onprocess();
+
+				// Write the output.
+				const outb = GodotRuntime.heapSub(HEAPF32, p_out_buf, p_out_size);
+				const output = event.outputBuffer;
+				const channels = output.numberOfChannels;
+				for (let ch = 0; ch < channels; ch++) {
+					const data = output.getChannelData(ch);
+					// Loop through samples and assign computed values.
+					for (let sample = 0; sample < data.length; sample++) {
+						data[sample] = outb[sample * channels + ch];
+					}
+				}
+			};
+			GodotAudioScript.script.connect(GodotAudio.ctx.destination);
+		},
+
+		get_node: function() {
+			return GodotAudioScript.script;
+		},
+
+		close: function() {
+			return new Promise(function(resolve, reject) {
+				GodotAudioScript.script.disconnect();
+				GodotAudioScript.script.onaudioprocess = null;
+				GodotAudioScript.script = null;
+				resolve();
+			});
+		},
+	},
+
+	godot_audio_script_create: function(buffer_length, channel_count) {
+		return GodotAudioScript.create(buffer_length, channel_count);
+	},
+
+	godot_audio_script_start: function(p_in_buf, p_in_size, p_out_buf, p_out_size, p_cb) {
+		const onprocess = GodotRuntime.get_func(p_cb);
+		GodotAudioScript.start(p_in_buf, p_in_size, p_out_buf, p_out_size, onprocess);
+	},
+};
+
+autoAddDeps(GodotAudioScript, "$GodotAudioScript");
+mergeInto(LibraryManager.library, GodotAudioScript);
diff --git a/platform/javascript/js/libs/library_godot_display.js b/platform/javascript/js/libs/library_godot_display.js
new file mode 100644
index 0000000000..28f63ba557
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_display.js
@@ -0,0 +1,477 @@
+/*************************************************************************/
+/*  library_godot_display.js                                             */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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.                */
+/*************************************************************************/
+
+/*
+ * Display Server listeners.
+ * Keeps track of registered event listeners so it can remove them on shutdown.
+ */
+const GodotDisplayListeners = {
+	$GodotDisplayListeners__deps: ['$GodotOS'],
+	$GodotDisplayListeners__postset: 'GodotOS.atexit(function(resolve, reject) { GodotDisplayListeners.clear(); resolve(); });',
+	$GodotDisplayListeners: {
+		handlers: [],
+
+		has: function(target, event, method, capture) {
+			return GodotDisplayListeners.handlers.findIndex(function(e) {
+				return e.target === target && e.event === event && e.method === method && e.capture === capture;
+			}) !== -1;
+		},
+
+		add: function(target, event, method, capture) {
+			if (GodotDisplayListeners.has(target, event, method, capture)) {
+				return;
+			}
+			function Handler(p_target, p_event, p_method, p_capture) {
+				this.target = p_target;
+				this.event = p_event;
+				this.method = p_method;
+				this.capture = p_capture;
+			};
+			GodotDisplayListeners.handlers.push(new Handler(target, event, method, capture));
+			target.addEventListener(event, method, capture);
+		},
+
+		clear: function() {
+			GodotDisplayListeners.handlers.forEach(function(h) {
+				h.target.removeEventListener(h.event, h.method, h.capture);
+			});
+			GodotDisplayListeners.handlers.length = 0;
+		},
+	},
+};
+mergeInto(LibraryManager.library, GodotDisplayListeners);
+
+/*
+ * Drag and drop handler.
+ * This is pretty big, but basically detect dropped files on GodotConfig.canvas,
+ * process them one by one (recursively for directories), and copies them to
+ * the temporary FS path '/tmp/drop-[random]/' so it can be emitted as a godot
+ * event (that requires a string array of paths).
+ *
+ * NOTE: The temporary files are removed after the callback. This means that
+ * deferred callbacks won't be able to access the files.
+ */
+const GodotDisplayDragDrop = {
+	$GodotDisplayDragDrop__deps: ['$FS', '$GodotFS'],
+	$GodotDisplayDragDrop: {
+		promises: [],
+		pending_files: [],
+
+		add_entry: function(entry) {
+			if (entry.isDirectory) {
+				GodotDisplayDragDrop.add_dir(entry);
+			} else if (entry.isFile) {
+				GodotDisplayDragDrop.add_file(entry);
+			} else {
+				GodotRuntime.error("Unrecognized entry...", entry);
+			}
+		},
+
+		add_dir: function(entry) {
+			GodotDisplayDragDrop.promises.push(new Promise(function(resolve, reject) {
+				const reader = entry.createReader();
+				reader.readEntries(function(entries) {
+					for (let i = 0; i < entries.length; i++) {
+						GodotDisplayDragDrop.add_entry(entries[i]);
+					}
+					resolve();
+				});
+			}));
+		},
+
+		add_file: function(entry) {
+			GodotDisplayDragDrop.promises.push(new Promise(function(resolve, reject) {
+				entry.file(function(file) {
+					const reader = new FileReader();
+					reader.onload = function() {
+						const f = {
+							"path": file.relativePath || file.webkitRelativePath,
+							"name": file.name,
+							"type": file.type,
+							"size": file.size,
+							"data": reader.result
+						};
+						if (!f['path']) {
+							f['path'] = f['name'];
+						}
+						GodotDisplayDragDrop.pending_files.push(f);
+						resolve()
+					};
+					reader.onerror = function() {
+						GodotRuntime.print("Error reading file");
+						reject();
+					}
+					reader.readAsArrayBuffer(file);
+				}, function(err) {
+					GodotRuntime.print("Error!");
+					reject();
+				});
+			}));
+		},
+
+		process: function(resolve, reject) {
+			if (GodotDisplayDragDrop.promises.length === 0) {
+				resolve();
+				return;
+			}
+			GodotDisplayDragDrop.promises.pop().then(function() {
+				setTimeout(function() {
+					GodotDisplayDragDrop.process(resolve, reject);
+				}, 0);
+			});
+		},
+
+		_process_event: function(ev, callback) {
+			ev.preventDefault();
+			if (ev.dataTransfer.items) {
+				// Use DataTransferItemList interface to access the file(s)
+				for (let i = 0; i < ev.dataTransfer.items.length; i++) {
+					const item = ev.dataTransfer.items[i];
+					let entry = null;
+					if ("getAsEntry" in item) {
+						entry = item.getAsEntry();
+					} else if ("webkitGetAsEntry" in item) {
+						entry = item.webkitGetAsEntry();
+					}
+					if (entry) {
+						GodotDisplayDragDrop.add_entry(entry);
+					}
+				}
+			} else {
+				GodotRuntime.error("File upload not supported");
+			}
+			new Promise(GodotDisplayDragDrop.process).then(function() {
+				const DROP = "/tmp/drop-" + parseInt(Math.random() * (1 << 30), 10) + "/";
+				const drops = [];
+				const files = [];
+				FS.mkdir(DROP);
+				GodotDisplayDragDrop.pending_files.forEach((elem) => {
+					const path = elem['path'];
+					GodotFS.copy_to_fs(DROP + path, elem['data']);
+					let idx = path.indexOf("/");
+					if (idx === -1) {
+						// Root file
+						drops.push(DROP + path);
+					} else {
+						// Subdir
+						const sub = path.substr(0, idx);
+						idx = sub.indexOf("/");
+						if (idx < 0 && drops.indexOf(DROP + sub) === -1) {
+							drops.push(DROP + sub);
+						}
+					}
+					files.push(DROP + path);
+				});
+				GodotDisplayDragDrop.promises = [];
+				GodotDisplayDragDrop.pending_files = [];
+				callback(drops);
+				const dirs = [DROP.substr(0, DROP.length -1)];
+				// Remove temporary files
+				files.forEach(function (file) {
+					FS.unlink(file);
+					let dir = file.replace(DROP, "");
+					let idx = dir.lastIndexOf("/");
+					while (idx > 0) {
+						dir = dir.substr(0, idx);
+						if (dirs.indexOf(DROP + dir) === -1) {
+							dirs.push(DROP + dir);
+						}
+						idx = dir.lastIndexOf("/");
+					}
+				});
+				// Remove dirs.
+				dirs.sort(function(a, b) {
+					const al = (a.match(/\//g) || []).length;
+					const bl = (b.match(/\//g) || []).length;
+					if (al > bl)
+						return -1;
+					else if (al < bl)
+						return 1;
+					return 0;
+				}).forEach(function(dir) {
+					FS.rmdir(dir);
+				});
+			});
+		},
+
+		handler: function(callback) {
+			return function(ev) {
+				GodotDisplayDragDrop._process_event(ev, callback);
+			};
+		},
+	},
+};
+mergeInto(LibraryManager.library, GodotDisplayDragDrop);
+
+/*
+ * Display server cursor helper.
+ * Keeps track of cursor status and custom shapes.
+ */
+const GodotDisplayCursor = {
+	$GodotDisplayCursor__deps: ['$GodotOS', '$GodotConfig'],
+	$GodotDisplayCursor__postset: 'GodotOS.atexit(function(resolve, reject) { GodotDisplayCursor.clear(); resolve(); });',
+	$GodotDisplayCursor: {
+		shape: 'auto',
+		visible: true,
+		cursors: {},
+		set_style: function(style) {
+			GodotConfig.canvas.style.cursor = style;
+		},
+		set_shape: function(shape) {
+			GodotDisplayCursor.shape = shape;
+			let css = shape;
+			if (shape in GodotDisplayCursor.cursors) {
+				const c = GodotDisplayCursor.cursors[shape];
+				css = 'url("' + c.url + '") ' + c.x + ' ' + c.y + ', auto';
+			}
+			if (GodotDisplayCursor.visible) {
+				GodotDisplayCursor.set_style(css);
+			}
+		},
+		clear: function() {
+			GodotDisplayCursor.set_style('');
+			GodotDisplayCursor.shape = 'auto';
+			GodotDisplayCursor.visible = true;
+			Object.keys(GodotDisplayCursor.cursors).forEach(function(key) {
+				URL.revokeObjectURL(GodotDisplayCursor.cursors[key]);
+				delete GodotDisplayCursor.cursors[key];
+			});
+		},
+	},
+};
+mergeInto(LibraryManager.library, GodotDisplayCursor);
+
+/**
+ * Display server interface.
+ *
+ * Exposes all the functions needed by DisplayServer implementation.
+ */
+const GodotDisplay = {
+	$GodotDisplay__deps: ['$GodotConfig', '$GodotRuntime', '$GodotDisplayCursor', '$GodotDisplayListeners', '$GodotDisplayDragDrop'],
+	$GodotDisplay: {
+		window_icon: '',
+	},
+
+	godot_js_display_is_swap_ok_cancel: function() {
+		const win = (['Windows', 'Win64', 'Win32', 'WinCE']);
+		const plat = navigator.platform || "";
+		if (win.indexOf(plat) !== -1) {
+			return 1;
+		}
+		return 0;
+	},
+
+	godot_js_display_alert: function(p_text) {
+		window.alert(GodotRuntime.parseString(p_text)); // eslint-disable-line no-alert
+	},
+
+	godot_js_display_pixel_ratio_get: function() {
+		return window.devicePixelRatio || 1;
+	},
+
+	/*
+	 * Canvas
+	 */
+	godot_js_display_canvas_focus: function() {
+		GodotConfig.canvas.focus();
+	},
+
+	godot_js_display_canvas_is_focused: function() {
+		return document.activeElement === GodotConfig.canvas;
+	},
+
+	godot_js_display_canvas_bounding_rect_position_get: function(r_x, r_y) {
+		const brect = GodotConfig.canvas.getBoundingClientRect();
+		GodotRuntime.setHeapValue(r_x, brect.x, 'i32');
+		GodotRuntime.setHeapValue(r_y, brect.y, 'i32');
+	},
+
+	/*
+	 * Touchscreen
+	 */
+	godot_js_display_touchscreen_is_available: function() {
+		return 'ontouchstart' in window;
+	},
+
+	/*
+	 * Clipboard
+	 */
+	godot_js_display_clipboard_set: function(p_text) {
+		const text = GodotRuntime.parseString(p_text);
+		if (!navigator.clipboard || !navigator.clipboard.writeText) {
+			return 1;
+		}
+		navigator.clipboard.writeText(text).catch(function(e) {
+			// Setting OS clipboard is only possible from an input callback.
+			GodotRuntime.error("Setting OS clipboard is only possible from an input callback for the HTML5 plafrom. Exception:", e);
+		});
+		return 0;
+	},
+
+	godot_js_display_clipboard_get: function(callback) {
+		const func = GodotRuntime.get_func(callback);
+		try {
+			navigator.clipboard.readText().then(function (result) {
+				const ptr = GodotRuntime.allocString(result);
+				func(ptr);
+				GodotRuntime.free(ptr);
+			}).catch(function (e) {
+				// Fail graciously.
+			});
+		} catch (e) {
+			// Fail graciously.
+		}
+	},
+
+	/*
+	 * Window
+	 */
+	godot_js_display_window_request_fullscreen: function() {
+		const canvas = GodotConfig.canvas;
+		(canvas.requestFullscreen || canvas.msRequestFullscreen ||
+			canvas.mozRequestFullScreen || canvas.mozRequestFullscreen ||
+			canvas.webkitRequestFullscreen
+		).call(canvas);
+	},
+
+	godot_js_display_window_title_set: function(p_data) {
+		document.title = GodotRuntime.parseString(p_data);
+	},
+
+	godot_js_display_window_icon_set: function(p_ptr, p_len) {
+		let link = document.getElementById('-gd-engine-icon');
+		if (link === null) {
+			link = document.createElement('link');
+			link.rel = 'icon';
+			link.id = '-gd-engine-icon';
+			document.head.appendChild(link);
+		}
+		const old_icon = GodotDisplay.window_icon;
+		const png = new Blob([GodotRuntime.heapCopy(HEAPU8, p_ptr, p_len)], { type: "image/png" });
+		GodotDisplay.window_icon = URL.createObjectURL(png);
+		link.href = GodotDisplay.window_icon;
+		if (old_icon) {
+			URL.revokeObjectURL(old_icon);
+		}
+	},
+
+	/*
+	 * Cursor
+	 */
+	godot_js_display_cursor_set_visible: function(p_visible) {
+		const visible = p_visible !== 0;
+		if (visible === GodotDisplayCursor.visible) {
+			return;
+		}
+		GodotDisplayCursor.visible = visible;
+		if (visible) {
+			GodotDisplayCursor.set_shape(GodotDisplayCursor.shape);
+		} else {
+			GodotDisplayCursor.set_style('none');
+		}
+	},
+
+	godot_js_display_cursor_is_hidden: function() {
+		return !GodotDisplayCursor.visible;
+	},
+
+	godot_js_display_cursor_set_shape: function(p_string) {
+		GodotDisplayCursor.set_shape(GodotRuntime.parseString(p_string));
+	},
+
+	godot_js_display_cursor_set_custom_shape: function(p_shape, p_ptr, p_len, p_hotspot_x, p_hotspot_y) {
+		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 url = URL.createObjectURL(png);
+			GodotDisplayCursor.cursors[shape] = {
+				url: url,
+				x: p_hotspot_x,
+				y: p_hotspot_y,
+			};
+		} else {
+			delete GodotDisplayCursor.cursors[shape];
+		}
+		if (shape === GodotDisplayCursor.shape) {
+			GodotDisplayCursor.set_shape(GodotDisplayCursor.shape);
+		}
+		if (old_shape) {
+			URL.revokeObjectURL(old_shape.url);
+		}
+	},
+
+	/*
+	 * Listeners
+	 */
+	godot_js_display_notification_cb: function(callback, p_enter, p_exit, p_in, p_out) {
+		const canvas = GodotConfig.canvas;
+		const func = GodotRuntime.get_func(callback);
+		const notif = [p_enter, p_exit, p_in, p_out];
+		['mouseover', 'mouseleave', 'focus', 'blur'].forEach(function(evt_name, idx) {
+			GodotDisplayListeners.add(canvas, evt_name, function() {
+				func.bind(null, notif[idx]);
+			}, true);
+		});
+	},
+
+	godot_js_display_paste_cb: function(callback) {
+		const func = GodotRuntime.get_func(callback);
+		GodotDisplayListeners.add(window, 'paste', function(evt) {
+			const text = evt.clipboardData.getData('text');
+			const ptr = GodotRuntime.allocString(text);
+			func(ptr);
+			GodotRuntime.free(ptr);
+		}, false);
+	},
+
+	godot_js_display_drop_files_cb: function(callback) {
+		const func = GodotRuntime.get_func(callback)
+		const dropFiles = function(files) {
+			const args = files || [];
+			if (!args.length) {
+				return;
+			}
+			const argc = args.length;
+			const argv = GodotRuntime.allocStringArray(args);
+			func(argv, argc);
+			GodotRuntime.freeStringArray(argv, argc);
+		};
+		const canvas = GodotConfig.canvas;
+		GodotDisplayListeners.add(canvas, 'dragover', function(ev) {
+			// Prevent default behavior (which would try to open the file(s))
+			ev.preventDefault();
+		}, false);
+		GodotDisplayListeners.add(canvas, 'drop', GodotDisplayDragDrop.handler(dropFiles));
+	},
+};
+
+autoAddDeps(GodotDisplay, '$GodotDisplay');
+mergeInto(LibraryManager.library, GodotDisplay);
diff --git a/platform/javascript/js/libs/library_godot_editor_tools.js b/platform/javascript/js/libs/library_godot_editor_tools.js
new file mode 100644
index 0000000000..21e40185ae
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_editor_tools.js
@@ -0,0 +1,56 @@
+/*************************************************************************/
+/*  library_godot_editor_tools.js                                        */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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 GodotEditorTools = {
+	godot_js_editor_download_file__deps: ['$FS'],
+	godot_js_editor_download_file: function(p_path, p_name, p_mime) {
+		const path = GodotRuntime.parseString(p_path);
+		const name = GodotRuntime.parseString(p_name);
+		const mime = GodotRuntime.parseString(p_mime);
+		const size = FS.stat(path)['size'];
+		const buf = new Uint8Array(size);
+		const fd = FS.open(path, 'r');
+		FS.read(fd, buf, 0, size);
+		FS.close(fd);
+		FS.unlink(path);
+		const blob = new Blob([buf], { type: mime });
+		const url = window.URL.createObjectURL(blob);
+		const a = document.createElement('a');
+		a.href = url;
+		a.download = name;
+		a.style.display = 'none';
+		document.body.appendChild(a);
+		a.click();
+		a.remove();
+		window.URL.revokeObjectURL(url);
+	},
+};
+
+mergeInto(LibraryManager.library, GodotEditorTools);
diff --git a/platform/javascript/js/libs/library_godot_eval.js b/platform/javascript/js/libs/library_godot_eval.js
new file mode 100644
index 0000000000..4064938d3e
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_eval.js
@@ -0,0 +1,87 @@
+/*************************************************************************/
+/*  library_godot_eval.js                                                */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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 GodotEval = {
+	godot_js_eval__deps: ['$GodotRuntime'],
+	godot_js_eval: function(p_js, p_use_global_ctx, p_union_ptr, p_byte_arr, p_byte_arr_write, p_callback) {
+		const js_code = GodotRuntime.parseString(p_js);
+		let eval_ret = null;
+		try {
+			if (p_use_global_ctx) {
+				// indirect eval call grants global execution context
+				const global_eval = eval; // eslint-disable-line no-eval
+				eval_ret = global_eval(js_code);
+			} else {
+				eval_ret = eval(js_code); // eslint-disable-line no-eval
+			}
+		} catch (e) {
+			GodotRuntime.error(e);
+		}
+
+		switch (typeof eval_ret) {
+
+			case 'boolean':
+				GodotRuntime.setHeapValue(p_union_ptr, eval_ret, 'i32');
+				return 1; // BOOL
+
+			case 'number':
+				GodotRuntime.setHeapValue(p_union_ptr, eval_ret, 'double');
+				return 3; // REAL
+
+			case 'string':
+				GodotRuntime.setHeapValue(p_union_ptr, GodotRuntime.allocString(eval_ret), '*');
+				return 4; // STRING
+
+			case 'object':
+				if (eval_ret === null) {
+					break;
+				}
+
+				if (ArrayBuffer.isView(eval_ret) && !(eval_ret instanceof Uint8Array)) {
+					eval_ret = new Uint8Array(eval_ret.buffer);
+				}
+				else if (eval_ret instanceof ArrayBuffer) {
+					eval_ret = new Uint8Array(eval_ret);
+				}
+				if (eval_ret instanceof Uint8Array) {
+					const func = GodotRuntime.get_func(p_callback);
+					const bytes_ptr = func(p_byte_arr, p_byte_arr_write,  eval_ret.length);
+					HEAPU8.set(eval_ret, bytes_ptr);
+					return 20; // POOL_BYTE_ARRAY
+				}
+				break;
+
+			// no default
+		}
+		return 0; // NIL
+	},
+}
+
+mergeInto(LibraryManager.library, GodotEval);
diff --git a/platform/javascript/js/libs/library_godot_http_request.js b/platform/javascript/js/libs/library_godot_http_request.js
new file mode 100644
index 0000000000..6f80f3b958
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_http_request.js
@@ -0,0 +1,143 @@
+/*************************************************************************/
+/*  http_request.js                                                      */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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() {
+			var idMax = GodotHTTPRequest.requests.length;
+			for (var 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: function() {
+		var newId = GodotHTTPRequest.getUnusedRequestId();
+		GodotHTTPRequest.requests[newId] = new XMLHttpRequest;
+		GodotHTTPRequest.setupRequest(GodotHTTPRequest.requests[newId]);
+		return newId;
+	},
+
+	godot_xhr_reset: function(xhrId) {
+		GodotHTTPRequest.requests[xhrId] = new XMLHttpRequest;
+		GodotHTTPRequest.setupRequest(GodotHTTPRequest.requests[xhrId]);
+	},
+
+	godot_xhr_free: function(xhrId) {
+		GodotHTTPRequest.requests[xhrId].abort();
+		GodotHTTPRequest.requests[xhrId] = null;
+	},
+
+	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: function(xhrId, header, value) {
+		GodotHTTPRequest.requests[xhrId].setRequestHeader(GodotRuntime.parseString(header), GodotRuntime.parseString(value));
+	},
+
+	godot_xhr_send_null: function(xhrId) {
+		GodotHTTPRequest.requests[xhrId].send();
+	},
+
+	godot_xhr_send_string: function(xhrId, strPtr) {
+		if (!strPtr) {
+			GodotRuntime.error("Failed to send string per XHR: null pointer");
+			return;
+		}
+		GodotHTTPRequest.requests[xhrId].send(GodotRuntime.parseString(strPtr));
+	},
+
+	godot_xhr_send_data: function(xhrId, ptr, len) {
+		if (!ptr) {
+			GodotRuntime.error("Failed to send data per XHR: null pointer");
+			return;
+		}
+		if (len < 0) {
+			GodotRuntime.error("Failed to send data per XHR: buffer length less than 0");
+			return;
+		}
+		GodotHTTPRequest.requests[xhrId].send(HEAPU8.subarray(ptr, ptr + len));
+	},
+
+	godot_xhr_abort: function(xhrId) {
+		GodotHTTPRequest.requests[xhrId].abort();
+	},
+
+	godot_xhr_get_status: function(xhrId) {
+		return GodotHTTPRequest.requests[xhrId].status;
+	},
+
+	godot_xhr_get_ready_state: function(xhrId) {
+		return GodotHTTPRequest.requests[xhrId].readyState;
+	},
+
+	godot_xhr_get_response_headers_length: function(xhrId) {
+		var headers = GodotHTTPRequest.requests[xhrId].getAllResponseHeaders();
+		return headers === null ? 0 : GodotRuntime.strlen(headers);
+	},
+
+	godot_xhr_get_response_headers: function(xhrId, dst, len) {
+		var str = GodotHTTPRequest.requests[xhrId].getAllResponseHeaders();
+		if (str === null)
+			return;
+		GodotRuntime.stringToHeap(str, dst, len);
+	},
+
+	godot_xhr_get_response_length: function(xhrId) {
+		var body = GodotHTTPRequest.requests[xhrId].response;
+		return body === null ? 0 : body.byteLength;
+	},
+
+	godot_xhr_get_response: function(xhrId, dst, len) {
+		var 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_os.js b/platform/javascript/js/libs/library_godot_os.js
new file mode 100644
index 0000000000..582f04cb1b
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_os.js
@@ -0,0 +1,280 @@
+/*************************************************************************/
+/*  library_godot_os.js                                                  */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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 IDHandler = {
+	$IDHandler: {
+		_last_id: 0,
+		_references: {},
+
+		get: function(p_id) {
+			return IDHandler._references[p_id];
+		},
+
+		add: function(p_data) {
+			const id = ++IDHandler._last_id;
+			IDHandler._references[id] = p_data;
+			return id;
+		},
+
+		remove: function(p_id) {
+			delete IDHandler._references[p_id];
+		},
+	},
+};
+
+autoAddDeps(IDHandler, "$IDHandler");
+mergeInto(LibraryManager.library, IDHandler);
+
+const GodotConfig = {
+	$GodotConfig__postset: 'Module["initConfig"] = GodotConfig.init_config;',
+	$GodotConfig__deps: ['$GodotRuntime'],
+	$GodotConfig: {
+		canvas: null,
+		locale: "en",
+		resize_on_start: false,
+		on_execute: null,
+
+		init_config: function(p_opts) {
+			GodotConfig.resize_on_start = p_opts['resizeCanvasOnStart'] ? true : false;
+			GodotConfig.canvas = p_opts['canvas'];
+			GodotConfig.locale = p_opts['locale'] || GodotConfig.locale;
+			GodotConfig.on_execute = p_opts['onExecute'];
+			// This is called by emscripten, even if undocumented.
+			Module['onExit'] = p_opts['onExit']; // eslint-disable-line no-undef
+		},
+
+		locate_file: function(file) {
+			return Module["locateFile"](file); // eslint-disable-line no-undef
+		},
+	},
+
+	godot_js_config_canvas_id_get: function(p_ptr, p_ptr_max) {
+		GodotRuntime.stringToHeap('#' + GodotConfig.canvas.id, p_ptr, p_ptr_max);
+	},
+
+	godot_js_config_locale_get: function(p_ptr, p_ptr_max) {
+		GodotRuntime.stringToHeap(GodotConfig.locale, p_ptr, p_ptr_max);
+	},
+
+	godot_js_config_is_resize_on_start: function() {
+		return GodotConfig.resize_on_start ? 1 : 0;
+	},
+};
+
+autoAddDeps(GodotConfig, '$GodotConfig');
+mergeInto(LibraryManager.library, GodotConfig);
+
+
+const GodotFS = {
+	$GodotFS__deps: ['$FS', '$IDBFS', '$GodotRuntime'],
+	$GodotFS__postset: [
+		'Module["initFS"] = GodotFS.init;',
+		'Module["deinitFS"] = GodotFS.deinit;',
+		'Module["copyToFS"] = GodotFS.copy_to_fs;',
+	].join(''),
+	$GodotFS: {
+		_idbfs: false,
+		_syncing: false,
+		_mount_points: [],
+
+		is_persistent: function() {
+			return GodotFS._idbfs ? 1 : 0;
+		},
+
+		// Initialize godot file system, setting up persistent paths.
+		// Returns a promise that resolves when the FS is ready.
+		// We keep track of mount_points, so that we can properly close the IDBFS
+		// since emscripten is not doing it by itself. (emscripten GH#12516).
+		init: function(persistentPaths) {
+			GodotFS._idbfs = false;
+			if (!Array.isArray(persistentPaths)) {
+				return Promise.reject(new Error('Persistent paths must be an array'));
+			}
+			if (!persistentPaths.length) {
+				return Promise.resolve();
+			}
+			GodotFS._mount_points = persistentPaths.slice();
+
+			function createRecursive(dir) {
+				try {
+					FS.stat(dir);
+				} catch (e) {
+					if (e.errno !== ERRNO_CODES.ENOENT) {
+						throw e;
+					}
+					FS.mkdirTree(dir);
+				}
+			}
+
+			GodotFS._mount_points.forEach(function(path) {
+				createRecursive(path);
+				FS.mount(IDBFS, {}, path);
+			});
+			return new Promise(function(resolve, reject) {
+				FS.syncfs(true, function(err) {
+					if (err) {
+						GodotFS._mount_points = [];
+						GodotFS._idbfs = false;
+						GodotRuntime.print("IndexedDB not available: " + err.message);
+					} else {
+						GodotFS._idbfs = true;
+					}
+					resolve(err);
+				});
+			});
+		},
+
+		// Deinit godot file system, making sure to unmount file systems, and close IDBFS(s).
+		deinit: function() {
+			GodotFS._mount_points.forEach(function(path) {
+				try {
+					FS.unmount(path);
+				} catch (e) {
+					GodotRuntime.print("Already unmounted", e);
+				}
+				if (GodotFS._idbfs && IDBFS.dbs[path]) {
+					IDBFS.dbs[path].close();
+					delete IDBFS.dbs[path];
+				}
+			});
+			GodotFS._mount_points = [];
+			GodotFS._idbfs = false;
+			GodotFS._syncing = false;
+		},
+
+		sync: function() {
+			if (GodotFS._syncing) {
+				GodotRuntime.error('Already syncing!');
+				return Promise.resolve();
+			}
+			GodotFS._syncing = true;
+			return new Promise(function (resolve, reject) {
+				FS.syncfs(false, function(error) {
+					if (error) {
+						GodotRuntime.error('Failed to save IDB file system: ' + error.message);
+					}
+					GodotFS._syncing = false;
+					resolve(error);
+				});
+			});
+		},
+
+		// Copies a buffer to the internal file system. Creating directories recursively.
+		copy_to_fs: function(path, buffer) {
+			const idx = path.lastIndexOf("/");
+			let dir = "/";
+			if (idx > 0) {
+				dir = path.slice(0, idx);
+			}
+			try {
+				FS.stat(dir);
+			} catch (e) {
+				if (e.errno !== ERRNO_CODES.ENOENT) {
+					throw e;
+				}
+				FS.mkdirTree(dir);
+			}
+			FS.writeFile(path, new Uint8Array(buffer), {'flags': 'wx+'});
+		},
+	},
+};
+mergeInto(LibraryManager.library, GodotFS);
+
+const GodotOS = {
+	$GodotOS__deps: ['$GodotFS', '$GodotRuntime'],
+	$GodotOS__postset: [
+		'Module["request_quit"] = function() { GodotOS.request_quit() };',
+		'GodotOS._fs_sync_promise = Promise.resolve();',
+	].join(''),
+	$GodotOS: {
+		request_quit: function() {},
+		_async_cbs: [],
+		_fs_sync_promise: null,
+
+		atexit: function(p_promise_cb) {
+			GodotOS._async_cbs.push(p_promise_cb);
+		},
+
+		finish_async: function(callback) {
+			GodotOS._fs_sync_promise.then(function(err) {
+				const promises = [];
+				GodotOS._async_cbs.forEach(function(cb) {
+					promises.push(new Promise(cb));
+				});
+				return Promise.all(promises);
+			}).then(function() {
+				return GodotFS.sync(); // Final FS sync.
+			}).then(function(err) {
+				// Always deferred.
+				setTimeout(function() {
+					callback();
+				}, 0);
+			});
+		},
+	},
+
+	godot_js_os_finish_async: function(p_callback) {
+		const func = GodotRuntime.get_func(p_callback);
+		GodotOS.finish_async(func);
+	},
+
+	godot_js_os_request_quit_cb: function(p_callback) {
+		GodotOS.request_quit = GodotRuntime.get_func(p_callback);
+	},
+
+	godot_js_os_fs_is_persistent: function() {
+		return GodotFS.is_persistent();
+	},
+
+	godot_js_os_fs_sync: function(callback) {
+		const func = GodotRuntime.get_func(callback);
+		GodotOS._fs_sync_promise = GodotFS.sync();
+		GodotOS._fs_sync_promise.then(function(err) {
+			func();
+		});
+	},
+
+	godot_js_os_execute: function(p_json) {
+		const json_args = GodotRuntime.parseString(p_json);
+		const args = JSON.parse(json_args);
+		if (GodotConfig.on_execute) {
+			GodotConfig.on_execute(args);
+			return 0;
+		}
+		return 1;
+	},
+
+	godot_js_os_shell_open: function(p_uri) {
+		window.open(GodotRuntime.parseString(p_uri), '_blank');
+	},
+};
+
+autoAddDeps(GodotOS, '$GodotOS');
+mergeInto(LibraryManager.library, GodotOS);
diff --git a/platform/javascript/js/libs/library_godot_runtime.js b/platform/javascript/js/libs/library_godot_runtime.js
new file mode 100644
index 0000000000..1769f83623
--- /dev/null
+++ b/platform/javascript/js/libs/library_godot_runtime.js
@@ -0,0 +1,120 @@
+/*************************************************************************/
+/*  library_godot_runtime.js                                             */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 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 GodotRuntime = {
+	$GodotRuntime: {
+		/*
+		 * Functions
+		 */
+		get_func: function(ptr) {
+			return wasmTable.get(ptr); // eslint-disable-line no-undef
+		},
+
+		/*
+		 * Prints
+		 */
+		error: function() {
+			err.apply(null, Array.from(arguments)); // eslint-disable-line no-undef
+		},
+
+		print: function() {
+			out.apply(null, Array.from(arguments)); // eslint-disable-line no-undef
+		},
+
+		/*
+		 * Memory
+		 */
+		malloc: function(p_size) {
+			return _malloc(p_size); // eslint-disable-line no-undef
+		},
+
+		free: function(p_ptr) {
+			_free(p_ptr); // eslint-disable-line no-undef
+		},
+
+		getHeapValue: function (p_ptr, p_type) {
+			return getValue(p_ptr, p_type); // eslint-disable-line no-undef
+		},
+
+		setHeapValue: function(p_ptr, p_value, p_type) {
+			setValue(p_ptr, p_value, p_type); // eslint-disable-line no-undef
+		},
+
+		heapSub: function(p_heap, p_ptr, p_len) {
+			const bytes = p_heap.BYTES_PER_ELEMENT;
+			return p_heap.subarray(p_ptr / bytes, p_ptr / bytes + p_len);
+		},
+
+		heapCopy: 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);
+		},
+
+		/*
+		 * Strings
+		 */
+		parseString: function(p_ptr) {
+			return UTF8ToString(p_ptr); // eslint-disable-line no-undef
+		},
+
+		strlen: function(p_str) {
+			return lengthBytesUTF8(p_str); // eslint-disable-line no-undef
+		},
+
+		allocString: function(p_str) {
+			const length = GodotRuntime.strlen(p_str)+1;
+			const c_str = GodotRuntime.malloc(length);
+			stringToUTF8(p_str, c_str, length); // eslint-disable-line no-undef
+			return c_str;
+		},
+
+		allocStringArray: function(p_strings) {
+			const size = p_strings.length;
+			const c_ptr = GodotRuntime.malloc(size * 4);
+			for (let i = 0; i < size; i++) {
+				HEAP32[(c_ptr >> 2) + i] = GodotRuntime.allocString(p_strings[i]);
+			}
+			return c_ptr;
+		},
+
+		freeStringArray: function(p_ptr, p_len) {
+			for (let i = 0; i < p_len; i++) {
+				GodotRuntime.free(HEAP32[(p_ptr >> 2) + i]);
+			}
+			GodotRuntime.free(p_ptr);
+		},
+
+		stringToHeap: function (p_str, p_ptr, p_len) {
+			return stringToUTF8Array(p_str, HEAP8, p_ptr, p_len); // eslint-disable-line no-undef
+		},
+	},
+};
+autoAddDeps(GodotRuntime, "$GodotRuntime");
+mergeInto(LibraryManager.library, GodotRuntime);