Firefox ChromeWorker not loading script - javascript

I have a requirement where I need to communicate with native code to perform some operations. I have been successful by using JS-Ctypes and things are panning out as expected. Since the communication from my web application with the native code takes some time, thus blocking the main JS thread consequently freezing the UI.
Thus I need to create a separate thread to be delegated with the communication with the native code and post back results to the main thread which will give the appropriate feedback to the user. Firefox ChromeWorker are exactly what I need to use, since they are independent threads with access to JS-Ctypes.
My problem is that for the life of me, I can't seem to load a script using that approach. This is what I currently have:
main.js
netscape.security.PrivilegeManager.enablePrivilege('UniversalXPConnect');
Components.utils.import("resource://gre/modules/Services.jsm");
var worker = new ChromeWorker("js/fpman/myworker.js");
worker.onmessage = function(e){
console.log(e.data);
};
worker.postMessage('start');
myworker.js
self.onmessage = function(e){
var sum = 1 + 1;
postMessage("Sum is " + sum);
};
When that code runs in the main JS, I get this error on firebug console
Failed to load script: http://localhost:8080/myapp/js/fpman/myworker.js (nsresult = 0x805303f4)
Point to note, when I use a normal worker thread i.e
var worker = new Worker("js/fpman/myworker.js");
the js file (myworker.js) is loaded fine and I get the expected result, but of course that doesn't suffice my needs since a normal worker doesn't have access to JS-Ctypes. So it seems the problem is how am creating the ChromeWorker. Could someone please enlighten me on how to appropriately instantiate and use the ChromeWorker Object from an application. I have seen a lot of reference of usage of ChromeWorker in extensions, but that is not what I want, I want to use the ChromeWorker in my web application.
Thanks.

That particular error is NS_ERROR_DOM_BAD_URI
I don't believe what you are doing will work, and I know it won't work very soon in Firefox because enablePrivilege is going away completely.

Related

Detect resource that hangs while loading with javascript

I have a bunch of functions that need to be called on $(window).on('load' ...). Occasionally, the site hangs indefinitely while loading. There are a bunch of embeds and other pieces of media being pulled in from various APIs.
Is it possible to detect what is still pending without attaching an event listener to every resource?
Edit for clarification:
#PamBlam's comment below was more tuned in to the problem -- I want to be able to do this with javascript, so it could happen client side while my users are browsing.
Specifically, I'd like to be able to identify pending requests and get any relevant details, and send a note to an error logger (such as sentry) to see what specific resources are problems for users on the live site. Perhaps the only solution would be to create a new loadResource function (as suggested in some answers) that compiles these details and, after a long timeout, sends a note to the logger if it still hasn't finished. But, this seems like overkill. Also some of these resources are <iframe>s that are included in the HTML, so more work to add that in.
What I was hoping for - and I'm guessing that this doesn't exist, as I assume javascript doesn't have permission to see what's happening on the browser level - was something that could, after a long time out, essentially look at the Network tab of dev tools and send a report of what is still pending.
One of the best ways to debug JavaScript is Chrome DevTools(while I am a big advocate of Firefox, in this case Chrome is just mind blowing). Use debug breakpoints and network to the best of your capabilities.
Appending the link for referral
https://developers.google.com/web/tools/chrome-devtools/
Count how many resources are loading, and decrement the count when each is finished. When the count is zero all resources are done.
var resourcesPending = 0;
// Load some resources
resourcesPending++;
loadAResource(function(){
resourcesPending--;
if(!resourcesPending) allResourcesLoaded();
});
resourcesPending++;
loadAResource(function(){
resourcesPending--;
if(!resourcesPending) allResourcesLoaded();
});
// etc..

how do you allow javascript communications with Flex/Flash/Actionscript

Well here's a problem.
I've got a website with large javascript backend. This backend talks to a server over a socket with a socket bridge using http://blog.deconcept.com/swfobject/
The socket "bridge" is a Flex/Flash .swf application/executable/plugin/thing for which the source is missing.
I've got to change it.
More facts:
file appExePluginThing.swf
appExePluginThing.swf Macromedia Flash data (compressed), version 9
I've used https://www.free-decompiler.com/flash/ to decompile the .swf file and I think I've sorted out what's the original code vs the libraries and things Flash/Flex built into it.
I've used FDT (the free version) to rebuild the decompiled code into MYappExePluginThing.swf so I can run it with the javascript code and see what happens.
I'm here because what happens isn't good. Basically, my javascript code (MYjavascript.js) gets to the point where it does
window.log("init()");
var so = new SWFObject("flash/MYappExePluginThing.swf"", socketObjectId, "0", "0", "9", "#FFFFFF");
window.log("init() created MYappExecPluginThing!!!");
so.addParam("allowScriptAccess", "always");
log("init() added Param!!");
so.write(elId);
log("init() wrote!");
IE9's console (yeah, you read that right) shows
init()
created MYappExecPluginThing!!!
init() added Param!!
init() wrote!
but none of the debugging i've got in MYappExePluginThing.as displays and nothing else happens.
I'm trying to figure out what I've screwed up/what's going on? Is MYappExePluginThing.as running? Is it waiting on something? Did it fail? Why aren't the log messages in MYappExePluginThing.as showing up?
The first most obvious thing is I'm using FDT which, I suspect, was not used to build the original. Is there some kind of magic "build javascript accessible swf thing" in FlashBuilder or some other IDE?
First noteworthy thing I find is:
file MYappExePluginThing.swf
MYappExePluginThing.swf Macromedia Flash data (compressed), version 14
I'm using Flex 4.6 which, for all I know, may have a completely different mechanism for allowing javascript communication than was used in appExePluginThing.swf
Does anyone know if that's true?
For example, when FDT runs this thing (I can compile but FDT does not create a .swf unless i run it) I get a warning in the following method:
private function init() : void
{
Log.log("console.log", "MYappExePluginThing init()");
//var initCallback:String = Application.application.parameters.initCallback?Application.application.parameters.initCallback:"MYjavascript.MYappExePluginThing_init";
var initCallback:String = FlexGlobals.topLevelApplication.parameters.initCallback?FlexGlobals.topLevelApplication.parameters.initCallback:"MYjavascript.MYappExePluginThing_init";
try
{
ExternalInterface.addCallback("method1Callback",method1);
ExternalInterface.addCallback("method2Callback",method2);
ExternalInterface.call(initCallback);
}
catch(err:Error)
{
Log.log("console.log", "MYappExePluginThing init() ERROR err="+err);
}
}
I got a warning that Application.application was deprecated and I should change:
var initCallback:String = Application.application.parameters.initCallback?Application.application.parameters.initCallback:"MYjavascript.MYappExePluginThing_init";
to:
var initCallback:String = FlexGlobals.topLevelApplication.parameters.initCallback?FlexGlobals.topLevelApplication.parameters.initCallback:"MYjavascript.MYappExePluginThing_init";
which I did but which had no effect on making the thing work.
(FYI Log.log() is something I added:
public class Log{
public static function log(dest:String, mssg:String):void{
if(ExternalInterface.available){
try{
ExternalInterface.call(dest, mssg);
}
catch(se:SecurityError){
}
catch(e:Error){
}
}
trace(mssg);
}
}
)
Additionally, in MYjavascript.js MYappExePluginThing_init looks like this:
this.MYappExePluginThing_init = function () {
log("MYjavascript.js - MYappExePluginThing_init:");
};
Its supposed to be executed when MYappExePluginThing finishes initializing itself.
Except its not. The message is NOT displaying on the console.
Unfortunately, I cannot find any references explaining how you allow javascript communication in Flex 4.6 so I can check if I've got this structured correctly.
Is it a built in kind of thing all Flex/Flash apps can do? Is my swf getting accessed? Is it having some kind of error? Is it unable to communicate back to my javascript?
Does anyone have any links to references?
If this was YOUR problem, what would you do next?
(Not a full solution but I ran out of room in the comment section.)
To answer your basic question, there's nothing special you should need to do to allow AS3-to-JS communication beyond what you've shown. However, you may have sandbox security issues on localhost; to avoid problems, set your SWFs as local-trusted (right-click Flash Player > Global Settings > Advanced > Trusted Location Settings). I'm guessing this not your problem, though, because you'd normally get a sandbox violation error.
More likely IMO is that something is broken due to decompilation and recompilation. SWFs aren't meant to do that, it's basically a hack made mostly possible due to SWF being an open format.
What I suggest is that you debug your running SWF. Using break-points and stepping through the code you should be able to narrow down where things are going wrong. You can also more easily see any errors your SWF is throwing.
Not really an answer, but an idea to get you started is to start logging everything on the Flash side to see where the breakage is.
Since you're using IE, I recommend getting the Debug flash player, installing it, then running Vizzy along side to show your traces.
Should give you a good idea of where the app is breaking down.
Vizzy
Debug Player

Web Workers for Parsing Raw Input in Chrome Packaged Calculator App

I am currently working on a calculator that will run as a packaged (desktop) chrome app. I am using the math.js library to parse math input. This is my old code:
evaluate.js:
var parser = math.parser();
function evaluate(input){
$("#output").text(parser.eval(input));
}
However, if the input is something unreasonable like 6234523412368492857483928!, the app just freezes, because it is trying to evaluate the input. I know that math.js is still in beta so eventually there might be a fix (overflow errors), but I couldn't find any other library that parses raw input the way math.js does.
To fix this, I am trying to fix this using web workers to run it asynchronously. Here is the code that I have right now:
main.js
var evaluator = new Worker('evaluate.js');
evaluator.addEventListener('message', function(e){
$("#output").text(e.data);
}, false);
function evaluate(input){
evaluator.postMessage(input);
}
evaluate.js
var parser = math.parser();
function mathEval(input){
return parser.eval(input);
}
self.addEventListener('message', function(e){
self.postMessage(mathEval(e.data));
});
However, this doesn't work when I run it. Also, I noticed that when I use web workers, it throws the error Uncaught ReferenceError: math is not defined - evaluate.js:1, but it didn't throw this error with the old code.
Questions: Why doesn't this code work to evaluate the input? Is it possible to use multiple workers to speed it up? If I wanted to implement some sort of overflow error for when the worker takes more than 2 seconds, what would be the best way to go about doing it? Finally, is there a better way to do this?
Web Workers are run in totally separate context. They don't have access to the objects from parent web page. If you want to use math.js you have to import it into the worker using importScript.
I recommend to read Using Web Workers guide, part "Importing Scripts And Libraries" which describes how to do it, and how it works in detail.

Firefox Extension: Access the DOM Before It's Loaded

I'm trying to create a Firefox extension that fires my Javascript code before any of the current page's Javascript is fired. My Javascript code will basically control whether or not the page's Javascript code can be executed or denied.
I first started out by trying to follow this answer, but I couldn't really figure out how to get it to work and realized I was relying on onDOMContentLoaded, which loads after the Javascript has already executed.
I then turned my attention toward XPCOM, but once again didn't really understand what the Firefox tutorials were telling me.
I've recently been trying to make an extension through Firebug, but I seem to hit the same problem... only having access to the Javascript after it's been parsed/executed. Here's the resulting code that I wrote. I think if I could access the file's objects in the onExamineResponse event, my problem could be solved, but I don't know how to do that... I'm talking about this code:
BeepbopListener.prototype = {
onRequest: function(context, file) {
...
},
onExamineResponse: function(context, file) {
FBTrace.sysout("onexamineresponse " + file); // this returns something like
// '[xpconnect wrapped (nsISupports, nsIHttpChannel, nsIRequest, nsIUploadChannel, nsITraceableChannel, nsIHttpChannelInternal)]'
// but I don't know how to access those elements...
var pattern = /\.js$/;
if (pattern.test(file.href) && FBTrace.DBG_BEEPBOP) {
FBTrace.sysout("ONEXAMINE DOESN'T EVEN GET IN THIS IF SO YOU WON'T SEE THIS");
}
},
...
};
So my question is... is there a tutorial out there that shows me how I can get access to all Javascript code on a page before it's executed? Also, if anyone has any helpful insight, I'd love to hear it. Oh, and if y'all need more code from me, just let me know, and I'll post it.
You can access a new document before any JavaScript code runs by listening to the content-document-global-created observer notification. However, the document will be empty at this point and JavaScript code will run as soon as the parser adds a <script> tag - you cannot really prevent it. Here are the options to control script execution that I am aware of.
1) Disable all JavaScript for a window using nsIDocShell.allowJavascript:
wnd.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
.getInterface(Components.interfaces.nsIWebNavigation)
.QueryInterface(Components.interfaces.nsIDocShell)
.allowJavascript = false;
This is an all or nothing approach. Note that JavaScript stays disabled even when a new document loads into the same frame.
2) Implement the nsIContentPolicy interface in an XPCOM component and register it in the content-policy category (via nsICategoryManager). Your shouldLoad() function will be able to block scripts selectively - but it will only called for external scripts (meaning <script src="...">), not for inline scripts on the page.
3) Use JavaScript debugger service to intercept script execution. You could use jsdIDebuggerService.interruptHook to step through JavaScript execution and abort the script whenever you like. But that would slow down JavaScript execution very significantly of course. At the very least you should use jsdIDebuggerService.addFilter() to restrict it to a particular document, otherwise you will slow down the entire browser (including browser UI).
I'm trying to create a Firefox extension that fires my Javascript code before any of the current page's Javascript is fired. My Javascript code will basically control whether or not the page's Javascript code can be executed or denied.
Start by completely preventing the document from getting parsed altogether then on the side, fetch the same document, do any processing on this document and then inject the resulting document in the page. Here is how I currently do just that https://stackoverflow.com/a/36097573/6085033

Connect Firefox extension with C# application

I need to be able to make an event such that every time a user loads a new page and closes firefox, I need it to call a method in my C# application that takes care of maintaining the user model. I know for sure I need to create some type of firefox extension where I use javascript to check such an event. However, I have no idea how I am going to integrate my C# application with the firefox extension. Can someone provide me with some guidance?
I'll help you out with the parts of the question that I'm familiar with (Javascript based add-ons), and offer some suggestions for the other parts. Here goes nothing!
Add-ons
Firefox add-ons easily provide the tools you need to detect page loads and opening / closing firefox.
To detect page loads you can register a listener to the DOMContentLoaded event in window.
window.addEventListener("DOMContentLoaded", function(event){
var url = event.originalTarget.location.href;
alert("Oh yeah, a document is loading: " + url);
}, false);
Alternatively, you can register a nsIWebProgressListener to listen for location changes. This probably closer to what you want, since DOMContentLoaded is also triggered for iframes.
var listener = {
//unimplemented methods (just give functions which do nothing)
onLocationChange: function(aWebProgress, aRequest, aLocation){
var url = aLocation.asciiSpec;
alert("Oh yeah, a the location changed: " + url);
}
};
gBrowser.addTabsProgressListener(listener);
To detect firefox open / close you need to first understand how firefox add-ons work with respect to multiple windows. When a new window of firefox is launched, you basically have 2 separate copies of your code running. So, if you care about firefox windows being opened and closed you can simply do:
window.addEventListener("load", function(event){
alert("Looks like you just opened up a new window");
}, false);
window.addEventListener("unload", function(event){
alert("Awh, you closed a window");
}, false);
But, most likely you want to detect opening / closing firefox as an entire application. This is achieved using a code-sharing mechanism called Javascript Modules. Javascript modules are loaded just once for the lifetime of the application. So, they enable you to share information between windows. Simply counting the number of windows opened and closed should be sufficient for this functionality.
var EXPORTED_SYMBOLS = ["windowOpened", "windowClosed"];
var windowsOpened = 0;
function windowOpened(){
if( windowsOpened === 0) {
alert("The first window has been opened!");
}
windowsOpened++;
}
function windowClosed(){
windowsOpened++;
if( windowsOpened === 0) {
alert("The last window has been closed!");
}
}
Then you can simply attach the aforementioned event handlers to call these 2 methods from their corresponding load and unload events.
So, this is all great and everything, but now you have to twiddle with the details of getting a baseline Firefox add-on setup. Fortunately, Mozilla has provided a handy Addon Builder to ease this. All the code about (except the Javascript module) should be placed in the ff-overlay.js file (assuming you use the linked builder).
C# communication
I'm a little less knowledgeable about the interprocess communication with C#. However, maybe I can point you in the right direction and let the smart people at SO fill in the rest.
I believe COM Objects are a method of communication between processes on Windows. So, you could build in a Binary Component to your add-on to perform the communication. However, as far as I understand it, setting up binary components is much more difficult than a standard javascript-based add-on. Either way, Mozilla provides a guide for setting it up in Visual Studio.
If you want to stay away from binary components you are left with the javascript enabled components of the SDK. This includes socket communication, files, pipes, a sqlite database etc. This SO question addresses exactly the question you're asking. If it were me, I would choose them in this order.
Sqlite Database
Named Pipes
Sockets
(1) because there is a lot of code samples available for this, and would be easy to implement on both sides. (2) because this would be the way I'd implement IPC if I were given full control of both sides of the application. (3) is last because I hate that crap (maybe I'm biased from Distributed Systems in college).
tl;dr
The page load stuff should be pretty simple. Check out the Addon Builder to get going with a FF addon, and here to see about detecting page loads.
The C# communication is doable, and addressed in this SO Question. I'd do it with a sqlite database for ease if it were me.

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