[HTML5] Refactor JS, threads support, closures.

- Refactored the Engine code, splitted across files.
- Use MODULARIZE option to build emscripten code into it's own closure.
- Enable lto support (saves ~2MiB in release).
- Enable optional closure compiler pass for JS and generated code.
- Enable optional pthreads support.
- Can now build with tools=yes (not much to see yet).
- Dropped some deprecated code for older toolchains.

5 files changed, 428 insertions, 0 deletions

diff --git a/platform/javascript/engine/engine.js b/platform/javascript/engine/engine.js
new file mode 100644
index 0000000000..6d7509377f
--- /dev/null
+++ b/platform/javascript/engine/engine.js
@@ -0,0 +1,184 @@
+Function('return this')()['Engine'] = (function() {
+
+	var unloadAfterInit = true;
+	var canvas = null;
+	var resizeCanvasOnStart = false;
+	var customLocale = 'en_US';
+	var wasmExt = '.wasm';
+
+	var preloader = new Preloader();
+	var loader = new Loader();
+	var rtenv = null;
+
+	var executableName = '';
+	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() {};
+
+	Engine.prototype.init = /** @param {string=} basePath */ function(basePath) {
+		if (initPromise) {
+			return initPromise;
+		}
+		if (!loadPromise) {
+			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;
+		initPromise = loader.init(loadPromise, loadPath, config).then(function() {
+			return new Promise(function(resolve, reject) {
+				rtenv = loader.env;
+				if (unloadAfterInit) {
+					loadPromise = null;
+				}
+				resolve();
+			});
+		});
+		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 new Promise(function(resolve, reject) {
+			return me.init().then(function() {
+				if (!(canvas instanceof HTMLCanvasElement)) {
+					canvas = Utils.findCanvas();
+				}
+				rtenv['locale'] = customLocale;
+				rtenv['canvas'] = canvas;
+				rtenv['thisProgram'] = executableName;
+				rtenv['resizeCanvasOnStart'] = resizeCanvasOnStart;
+				loader.start(preloader.preloadedFiles, args).then(function() {
+					loader = null;
+					initPromise = null;
+					resolve();
+				});
+			});
+		});
+	};
+
+	Engine.prototype.startGame = function(execName, mainPack) {
+		// Start and init with execName as loadPath if not inited.
+		executableName = execName;
+		var me = this;
+		return Promise.all([
+			this.init(execName),
+			this.preloadFile(mainPack, mainPack)
+		]).then(function() {
+			return me.start('--main-pack', mainPack);
+		});
+	};
+
+	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) {
+		canvas = canvasElem;
+	};
+
+	Engine.prototype.setCanvasResizedOnStart = function(enabled) {
+		resizeCanvasOnStart = enabled;
+	};
+
+	Engine.prototype.setLocale = function(locale) {
+		customLocale = locale;
+	};
+
+	Engine.prototype.setExecutableName = function(newName) {
+		executableName = newName;
+	};
+
+	Engine.prototype.setProgressFunc = function(func) {
+		progressFunc = func;
+	}
+
+	Engine.prototype.setStdoutFunc = function(func) {
+
+		var print = function(text) {
+			if (arguments.length > 1) {
+				text = Array.prototype.slice.call(arguments).join(" ");
+			}
+			func(text);
+		};
+		if (rtenv)
+			rtenv.print = print;
+		stdout = print;
+	};
+
+	Engine.prototype.setStderrFunc = function(func) {
+
+		var printErr = function(text) {
+			if (arguments.length > 1)
+				text = Array.prototype.slice.call(arguments).join(" ");
+			func(text);
+		};
+		if (rtenv)
+			rtenv.printErr = printErr;
+		stderr = printErr;
+	};
+
+	// 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
+	return Engine;
+})();
diff --git a/platform/javascript/engine/externs.js b/platform/javascript/engine/externs.js
new file mode 100644
index 0000000000..1a94dd15ec
--- /dev/null
+++ b/platform/javascript/engine/externs.js
@@ -0,0 +1,3 @@
+var Godot;
+var WebAssembly = {};
+WebAssembly.instantiate = function(buffer, imports) {};
diff --git a/platform/javascript/engine/loader.js b/platform/javascript/engine/loader.js
new file mode 100644
index 0000000000..d27fbf612e
--- /dev/null
+++ b/platform/javascript/engine/loader.js
@@ -0,0 +1,33 @@
+var Loader = /** @constructor */ function() {
+
+	this.env = null;
+
+	this.init = function(loadPromise, basePath, config) {
+		var me = this;
+		return new Promise(function(resolve, reject) {
+			var cfg = config || {};
+			cfg['locateFile'] = Utils.createLocateRewrite(basePath);
+			cfg['instantiateWasm'] = Utils.createInstantiatePromise(loadPromise);
+			loadPromise = null;
+			Godot(cfg).then(function(module) {
+				me.env = module;
+				resolve();
+			});
+		});
+	}
+
+	this.start = function(preloadedFiles, args) {
+		var me = this;
+		return new Promise(function(resolve, reject) {
+			if (!me.env) {
+				reject(new Error('The engine must be initialized before it can be started'));
+			}
+			preloadedFiles.forEach(function(file) {
+				Utils.copyToFS(me.env['FS'], file.path, file.buffer);
+			});
+			preloadedFiles.length = 0; // Clear memory
+			me.env['callMain'](args);
+			resolve();
+		});
+	}
+};
diff --git a/platform/javascript/engine/preloader.js b/platform/javascript/engine/preloader.js
new file mode 100644
index 0000000000..17918eae38
--- /dev/null
+++ b/platform/javascript/engine/preloader.js
@@ -0,0 +1,139 @@
+var Preloader = /** @constructor */ function() {
+
+	var DOWNLOAD_ATTEMPTS_MAX = 4;
+	var progressFunc = null;
+	var lastProgress = { loaded: 0, total: 0 };
+
+	var loadingFiles = {};
+	this.preloadedFiles = [];
+
+	function loadXHR(resolve, reject, file, tracker) {
+		var xhr = new XMLHttpRequest;
+		xhr.open('GET', file);
+		if (!file.endsWith('.js')) {
+			xhr.responseType = 'arraybuffer';
+		}
+		['loadstart', 'progress', 'load', 'error', 'abort'].forEach(function(ev) {
+			xhr.addEventListener(ev, onXHREvent.bind(xhr, resolve, reject, file, tracker));
+		});
+		xhr.send();
+	}
+
+	function onXHREvent(resolve, reject, file, tracker, ev) {
+
+		if (this.status >= 400) {
+
+			if (this.status < 500 || ++tracker[file].attempts >= DOWNLOAD_ATTEMPTS_MAX) {
+				reject(new Error("Failed loading file '" + file + "': " + this.statusText));
+				this.abort();
+				return;
+			} else {
+				setTimeout(loadXHR.bind(null, resolve, reject, file, tracker), 1000);
+			}
+		}
+
+		switch (ev.type) {
+			case 'loadstart':
+				if (tracker[file] === undefined) {
+					tracker[file] = {
+						total: ev.total,
+						loaded: ev.loaded,
+						attempts: 0,
+						final: false,
+					};
+				}
+				break;
+
+			case 'progress':
+				tracker[file].loaded = ev.loaded;
+				tracker[file].total = ev.total;
+				break;
+
+			case 'load':
+				tracker[file].final = true;
+				resolve(this);
+				break;
+
+			case 'error':
+				if (++tracker[file].attempts >= DOWNLOAD_ATTEMPTS_MAX) {
+					tracker[file].final = true;
+					reject(new Error("Failed loading file '" + file + "'"));
+				} else {
+					setTimeout(loadXHR.bind(null, resolve, reject, file, tracker), 1000);
+				}
+				break;
+
+			case 'abort':
+				tracker[file].final = true;
+				reject(new Error("Loading file '" + file + "' was aborted."));
+				break;
+		}
+	}
+
+	this.loadPromise = function(file) {
+		return new Promise(function(resolve, reject) {
+			loadXHR(resolve, reject, file, loadingFiles);
+		});
+	}
+
+	this.preload = function(pathOrBuffer, destPath) {
+		if (pathOrBuffer instanceof ArrayBuffer) {
+			pathOrBuffer = new Uint8Array(pathOrBuffer);
+		} else if (ArrayBuffer.isView(pathOrBuffer)) {
+			pathOrBuffer = new Uint8Array(pathOrBuffer.buffer);
+		}
+		if (pathOrBuffer instanceof Uint8Array) {
+			this.preloadedFiles.push({
+				path: destPath,
+				buffer: pathOrBuffer
+			});
+			return Promise.resolve();
+		} else 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 {
+			throw Promise.reject("Invalid object for preloading");
+		}
+	};
+
+	var 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; // Also exposed to start it.
+
+	this.setProgressFunc = function(callback) {
+		progressFunc = callback;
+	}
+};
diff --git a/platform/javascript/engine/utils.js b/platform/javascript/engine/utils.js
new file mode 100644
index 0000000000..fdff90a923
--- /dev/null
+++ b/platform/javascript/engine/utils.js
@@ -0,0 +1,69 @@
+var Utils = {
+
+	createLocateRewrite: function(execName) {
+		function rw(path) {
+			if (path.endsWith('.worker.js')) {
+				return execName + '.worker.js';
+			} else if (path.endsWith('.js')) {
+				return execName + '.js';
+			} else if (path.endsWith('.wasm')) {
+				return execName + '.wasm';
+			}
+		}
+		return rw;
+	},
+
+	createInstantiatePromise: function(wasmLoader) {
+		function instantiateWasm(imports, onSuccess) {
+			wasmLoader.then(function(xhr) {
+				WebAssembly.instantiate(xhr.response, imports).then(function(result) {
+					onSuccess(result['instance'], result['module']);
+				});
+			});
+			wasmLoader = null;
+			return {};
+		};
+
+		return instantiateWasm;
+	},
+
+	copyToFS: function(fs, path, buffer) {
+		var p = path.lastIndexOf("/");
+		var dir = "/";
+		if (p > 0) {
+			dir = path.slice(0, path.lastIndexOf("/"));
+		}
+		try {
+			fs.stat(dir);
+		} catch (e) {
+			if (e.errno !== 44) { // 'ENOENT', see https://github.com/emscripten-core/emscripten/blob/master/system/lib/libc/musl/arch/emscripten/bits/errno.h
+				throw e;
+			}
+			fs['mkdirTree'](dir);
+		}
+		// With memory growth, canOwn should be false.
+		fs['writeFile'](path, new Uint8Array(buffer), {'flags': 'wx+'});
+	},
+
+	findCanvas: function() {
+		var nodes = document.getElementsByTagName('canvas');
+		if (nodes.length && nodes[0] instanceof HTMLCanvasElement) {
+			return nodes[0];
+		}
+		throw new Error("No canvas found");
+	},
+
+	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) {}
+		return !!testContext;
+	}
+};