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Use XHR to load worker only if needed
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Rather than always loading the pdf.worker.js source through XHR,
first try creating a worker using the pdf.worker.js url. If that
fails, use XHR. If that also fails, use a fake worker.

Removed some earlier changes that ware unnecessary.
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@jasny
jasny committed Jul 20, 2016
1 parent 92f1c14 commit 942b571
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Showing 3 changed files with 185 additions and 129 deletions.
139 changes: 81 additions & 58 deletions README.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -186,65 +186,88 @@ We need to check if the viewer is initialized, before handling the event.
+ // Ignore mousewheel event if pdfViewer isn't loaded
+ if (!PDFViewerApplication.pdfViewer) return;

#### Load code for worker using AJAX
#### Load code for worker using AJAX if needed

A [Web Worker](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers) can't use code from
a same-origin domain. The CORS headers don't apply (they do work in some browsers, but not in all).

To get around this, the source code of the worker is fetched using AJAX and presented as blob.

var WorkerTransport = (function WorkerTransportClosure() {
function WorkerTransport(workerInitializedCapability, pdfDataRangeTransport) {
+ /**
+ * Needed because workers cannot load scripts outside of the current origin (as of firefox v45).
+ * This patch does require the worker script to be served with a (Access-Control-Allow-Origin: *) header
+ * @patch
+ */
+ globalScope.cachedJSDfd = null;
+ this.loadWorkerXHR = function(url){
+ if (globalScope.cachedJSDfd) { return globalScope.cachedJSDfd; }
+ globalScope.cachedJSDfd = PDFJS.createPromiseCapability();
+
+ var xmlhttp;
+ xmlhttp = new XMLHttpRequest();
+
+ xmlhttp.onreadystatechange = function(){
+ if (xmlhttp.readyState == 4 && xmlhttp.status == 200){
+ var workerJSBlob = new Blob([xmlhttp.responseText], { type: 'text/javascript' });
+ globalScope.cachedJSDfd.resolve(window.URL.createObjectURL(workerJSBlob));
+ }
+ };
+
+ xmlhttp.open('GET', url, true);
+ xmlhttp.send();
+ return globalScope.cachedJSDfd.promise;
+ }

Instead of simply starting the worker, we need to get the code and than start it.

+ this.loadWorkerXHR(workerSrc).then(function(blob) {
+ workerSrc = PDFJS.workerSrc = blob;
+
try {
// Some versions of FF can't create a worker on localhost, see:
// https://bugzilla.mozilla.org/show_bug.cgi?id=683280
@@ -3589,11 +3618,16 @@
return;
} catch (e) {
info('The worker has been disabled.');
+ this.setupFakeWorker();
a same-origin domain. The CORS headers don't apply.

he patch will cause pdf.js to first try to create the Worker the regular way, with a URL to the JavaScript source. If
this fails, the source if fetched using AJAX and used to create an
[object url](https://developer.mozilla.org/en-US/docs/Web/API/URL/createObjectURL). If this also fails, pdf.js will go
onto it's last resort by calling `setupFakeWorker()`.

+ /**
+ * Needed because workers cannot load scripts outside of the current origin (as of firefox v45).
+ * This patch does require the worker script to be served with a (Access-Control-Allow-Origin: *) header
+ * @patch
+ */
+ var loadWorkerXHR = function(){
+ var url = PDFJS.workerSrc;
+ var jsdfd = PDFJS.createPromiseCapability();
+
+ if (url.match(/^blob:/) || typeof URL.createObjectURL === 'undefined') {
+ jsdfd.reject(); // Failed loading using blob
+ }
+
+ var xmlhttp;
+ xmlhttp = new XMLHttpRequest();
+
+ xmlhttp.onreadystatechange = function(){
+ if (xmlhttp.readyState != 4) return;
+
+ if (xmlhttp.status == 200) {
+ info('Loaded worker source through XHR.');
+ var workerJSBlob = new Blob([xmlhttp.responseText], { type: 'text/javascript' });
+ jsdfd.resolve(window.URL.createObjectURL(workerJSBlob));
+ } else {
+ jsdfd.reject();
+ }
+ };
+
+ xmlhttp.open('GET', url, true);
+ xmlhttp.send();
+ return jsdfd.promise;
+ }
+
+ var workerError = function() {
+ loadWorkerXHR().then(function(blob) {
+ PDFJS.workerSrc = blob;
+ loadWorker();
+ }, function() {
+ this.setupFakeWorker();
+ }.bind(this));
+ }.bind(this);
+

- if (!globalScope.PDFJS.disableWorker && typeof Worker !== 'undefined') {
+ var loadWorker = function() {
var workerSrc = PDFJS.workerSrc;
if (!workerSrc) {
error('No PDFJS.workerSrc specified');
@@ -3559,6 +3603,8 @@
// Some versions of FF can't create a worker on localhost, see:
// https://bugzilla.mozilla.org/show_bug.cgi?id=683280
var worker = new Worker(workerSrc);
+ worker.onerror = workerError;
+
var messageHandler = new MessageHandler('main', worker);
this.messageHandler = messageHandler;

@@ -3589,11 +3635,16 @@
return;
} catch (e) {
info('The worker has been disabled.');
+ workerError();
}
- }
+ }.bind(this);
// Either workers are disabled, not supported or have thrown an exception.
// Thus, we fallback to a faked worker.
- this.setupFakeWorker();
+ if (!globalScope.PDFJS.disableWorker && typeof Worker !== 'undefined') {
+ loadWorker();
+ } else {
+ this.setupFakeWorker();
+ }
}
+
+ }.bind(this));
}

As the worker is started async, we only start the worker on an error, when the browser doesn't support web workers or
when it's explicitly set that we don't want to use the web worker api.

// Either workers are disabled, not supported or have thrown an exception.
// Thus, we fallback to a faked worker.
- this.setupFakeWorker();
+ if (globalScope.PDFJS.disableWorker || typeof Worker === 'undefined') {
+ this.setupFakeWorker();
+ }

67 changes: 42 additions & 25 deletions pdf.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1086,6 +1086,7 @@ PDFJS.build = 'c9a7498';
'use strict';

var globalScope = (typeof window === 'undefined') ? this : window;

var isWorker = (typeof window === 'undefined');

var FONT_IDENTITY_MATRIX = [0.001, 0, 0, 0.001, 0, 0];
Expand Down Expand Up @@ -3535,59 +3536,75 @@ var PDFPageProxy = (function PDFPageProxyClosure() {
*/
var WorkerTransport = (function WorkerTransportClosure() {
function WorkerTransport(workerInitializedCapability, pdfDataRangeTransport) {
this.pdfDataRangeTransport = pdfDataRangeTransport;
this.workerInitializedCapability = workerInitializedCapability;
this.commonObjs = new PDFObjects();

this.loadingTask = null;

this.pageCache = [];
this.pagePromises = [];
this.downloadInfoCapability = createPromiseCapability();

/**
* Needed because workers cannot load scripts outside of the current origin (as of firefox v45).
* This patch does require the worker script to be served with a (Access-Control-Allow-Origin: *) header
* @patch
*/
globalScope.cachedJSDfd = null;
this.loadWorkerXHR = function(url){
if (globalScope.cachedJSDfd) { return globalScope.cachedJSDfd; }
globalScope.cachedJSDfd = PDFJS.createPromiseCapability();
var loadWorkerXHR = function(){
var url = PDFJS.workerSrc;
var jsdfd = PDFJS.createPromiseCapability();

if (url.match(/^blob:/) || typeof URL.createObjectURL === 'undefined') {
jsdfd.reject(); // Failed loading using blob
}

var xmlhttp;
xmlhttp = new XMLHttpRequest();

xmlhttp.onreadystatechange = function(){
if (xmlhttp.readyState == 4 && xmlhttp.status == 200){
if (xmlhttp.readyState != 4) return;

if (xmlhttp.status == 200) {
info('Loaded worker source through XHR.');
var workerJSBlob = new Blob([xmlhttp.responseText], { type: 'text/javascript' });
globalScope.cachedJSDfd.resolve(window.URL.createObjectURL(workerJSBlob));
jsdfd.resolve(window.URL.createObjectURL(workerJSBlob));
} else {
jsdfd.reject();
}
};

xmlhttp.open('GET', url, true);
xmlhttp.send();
return globalScope.cachedJSDfd.promise;
return jsdfd.promise;
}

this.pdfDataRangeTransport = pdfDataRangeTransport;
this.workerInitializedCapability = workerInitializedCapability;
this.commonObjs = new PDFObjects();

this.loadingTask = null;

this.pageCache = [];
this.pagePromises = [];
this.downloadInfoCapability = createPromiseCapability();
var workerError = function() {
loadWorkerXHR().then(function(blob) {
PDFJS.workerSrc = blob;
loadWorker();
}, function() {
this.setupFakeWorker();
}.bind(this));
}.bind(this);

// If worker support isn't disabled explicit and the browser has worker
// support, create a new web worker and test if it/the browser fullfills
// all requirements to run parts of pdf.js in a web worker.
// Right now, the requirement is, that an Uint8Array is still an Uint8Array
// as it arrives on the worker. Chrome added this with version 15.
if (!globalScope.PDFJS.disableWorker && typeof Worker !== 'undefined') {
var loadWorker = function() {
var workerSrc = PDFJS.workerSrc;
if (!workerSrc) {
error('No PDFJS.workerSrc specified');
}

this.loadWorkerXHR(workerSrc).then(function(blob) {
workerSrc = PDFJS.workerSrc = blob;

try {
// Some versions of FF can't create a worker on localhost, see:
// https://bugzilla.mozilla.org/show_bug.cgi?id=683280
var worker = new Worker(workerSrc);
worker.onerror = workerError;

var messageHandler = new MessageHandler('main', worker);
this.messageHandler = messageHandler;

Expand Down Expand Up @@ -3618,14 +3635,14 @@ var WorkerTransport = (function WorkerTransportClosure() {
return;
} catch (e) {
info('The worker has been disabled.');
this.setupFakeWorker();
workerError();
}

}.bind(this));
}
}.bind(this);
// Either workers are disabled, not supported or have thrown an exception.
// Thus, we fallback to a faked worker.
if (globalScope.PDFJS.disableWorker || typeof Worker === 'undefined') {
if (!globalScope.PDFJS.disableWorker && typeof Worker !== 'undefined') {
loadWorker();
} else {
this.setupFakeWorker();
}
}
Expand Down
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