140 lines
3.4 KiB
JavaScript
140 lines
3.4 KiB
JavaScript
var Preloader = /** @constructor */ function() {
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var DOWNLOAD_ATTEMPTS_MAX = 4;
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var progressFunc = null;
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var lastProgress = { loaded: 0, total: 0 };
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var loadingFiles = {};
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this.preloadedFiles = [];
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function loadXHR(resolve, reject, file, tracker) {
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var xhr = new XMLHttpRequest;
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xhr.open('GET', file);
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if (!file.endsWith('.js')) {
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xhr.responseType = 'arraybuffer';
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}
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['loadstart', 'progress', 'load', 'error', 'abort'].forEach(function(ev) {
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xhr.addEventListener(ev, onXHREvent.bind(xhr, resolve, reject, file, tracker));
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});
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xhr.send();
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}
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function onXHREvent(resolve, reject, file, tracker, ev) {
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if (this.status >= 400) {
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if (this.status < 500 || ++tracker[file].attempts >= DOWNLOAD_ATTEMPTS_MAX) {
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reject(new Error("Failed loading file '" + file + "': " + this.statusText));
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this.abort();
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return;
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} else {
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setTimeout(loadXHR.bind(null, resolve, reject, file, tracker), 1000);
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}
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}
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switch (ev.type) {
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case 'loadstart':
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if (tracker[file] === undefined) {
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tracker[file] = {
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total: ev.total,
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loaded: ev.loaded,
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attempts: 0,
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final: false,
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};
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}
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break;
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case 'progress':
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tracker[file].loaded = ev.loaded;
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tracker[file].total = ev.total;
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break;
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case 'load':
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tracker[file].final = true;
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resolve(this);
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break;
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case 'error':
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if (++tracker[file].attempts >= DOWNLOAD_ATTEMPTS_MAX) {
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tracker[file].final = true;
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reject(new Error("Failed loading file '" + file + "'"));
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} else {
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setTimeout(loadXHR.bind(null, resolve, reject, file, tracker), 1000);
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}
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break;
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case 'abort':
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tracker[file].final = true;
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reject(new Error("Loading file '" + file + "' was aborted."));
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break;
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}
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}
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this.loadPromise = function(file) {
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return new Promise(function(resolve, reject) {
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loadXHR(resolve, reject, file, loadingFiles);
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});
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}
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this.preload = function(pathOrBuffer, destPath) {
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if (pathOrBuffer instanceof ArrayBuffer) {
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pathOrBuffer = new Uint8Array(pathOrBuffer);
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} else if (ArrayBuffer.isView(pathOrBuffer)) {
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pathOrBuffer = new Uint8Array(pathOrBuffer.buffer);
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}
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if (pathOrBuffer instanceof Uint8Array) {
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this.preloadedFiles.push({
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path: destPath,
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buffer: pathOrBuffer
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});
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return Promise.resolve();
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} else if (typeof pathOrBuffer === 'string') {
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var me = this;
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return this.loadPromise(pathOrBuffer).then(function(xhr) {
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me.preloadedFiles.push({
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path: destPath || pathOrBuffer,
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buffer: xhr.response
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});
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return Promise.resolve();
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});
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} else {
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throw Promise.reject("Invalid object for preloading");
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}
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};
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var animateProgress = function() {
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var loaded = 0;
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var total = 0;
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var totalIsValid = true;
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var progressIsFinal = true;
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Object.keys(loadingFiles).forEach(function(file) {
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const stat = loadingFiles[file];
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if (!stat.final) {
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progressIsFinal = false;
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}
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if (!totalIsValid || stat.total === 0) {
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totalIsValid = false;
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total = 0;
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} else {
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total += stat.total;
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}
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loaded += stat.loaded;
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});
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if (loaded !== lastProgress.loaded || total !== lastProgress.total) {
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lastProgress.loaded = loaded;
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lastProgress.total = total;
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if (typeof progressFunc === 'function')
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progressFunc(loaded, total);
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}
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if (!progressIsFinal)
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requestAnimationFrame(animateProgress);
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}
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this.animateProgress = animateProgress; // Also exposed to start it.
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this.setProgressFunc = function(callback) {
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progressFunc = callback;
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}
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};
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