How to make JS wait until protocol execution finished

Question

I have a custom URL protocol handler cgit:[...]

It launches up a background process which configures some stuff on the local machine. The protocol works fine, i'm launching it from JavaScript (currently using document.location = 'cgit:[...]'), but i actually want JavaScript to wait until the associated program exits.

---

So basically the steps i want JavaScript to do:

1. JavaScript does something

2. JavaScript launches cgit:[...]

3. Javascript waits until cgit:[...] exits

4. JavaScript does something else

---

Code:

function launchCgit(params)
{
    showProgressBar();
    document.location="cgit:"+params;
    document.addEventListener( /* CGit-Program exited event */, hideProgressBar );
}

or:

function launchCgit(params)
{
    showProgressBar();
    // setLocationAndWait("cgit:"+params);
    hideProgressBar();
}

---

Any ideas if this is possible?

Answer 1

As i didn't find a suitable way to solve my problem using ajax requests or anything similar, i finally solved my problem using a kind-of-ugly workarround including XmlHttpRequest

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For launching the protocol i'm still using document.location=cgit:[...]

I'm using a server side system including "lock-files" - that's like generic dummy files, with generated names for each request.

Once the user requests to open the custom protocol, such a file is being generated on the server specifically for that one protocol-opening-request.

I created a folder called "$locks" on the server where these files are being placed in. Once the protocol-associated program exits, the appropriate file is being deleted.

The website continuously checks if the file for a request still exists using XmlHttpRequest and fires a callback if it doesn't (example timout between tests: 1 sec).

The structure of the new files is the following:

• lockThisRequest.php: It creates a file in the $locks directory based on the req url-parameter.
• unlockThisRequest.php: It deletes a file in the $locks directory; again based on the req url-parameter.

The JavaScript part of it goes:

function launchCgit(params,callback)
{
    var lock = /* Generate valid filename from params variable */;

    // "Lock" that Request (means: telling the server that a request with this ID is now in use)
    var locker = new XmlHttpRequest();
    locker.open('GET', 'lockThisRequest.php?req='+lock, true)
    locker.send(null);

    function retry()
    {
        // Test if the lock-file still exists on the server
        var req = new XmlHttpRequest();
        req.open('GET', '$locks/'+lock, true);
        req.onReadyStateChanged=function()
        {
            if (req.readyState == 4)
            {
                if (req.status == 200)
                {
                    // lock-file exists -> cgit has not exited yet
                    window.setTimeout(retry,1000);
                }
                else if (req.status == 404)
                {
                    // lock-file not found -> request has been proceeded
                    callback();
                }
            }
        }
        req.send(null);
    }
    document.location = 'cgit:'+params; // execute custom protocol
    retry(); // initialize lockfileCheck-loop
}

Ussage is:

launchCgit("doThisAndThat",function()
                           {
                               alert("ThisAndThat finished.");
                           });

the lockThisRequest.php-file:

<?php
    file_put_contents("$locks/".$_GET["req"],""); // Create lock file
?>

and unlockThisRequest.php:

<?php
    unlink("../\$locks/".$_GET["req"]); // Delete lock file
?>

---

The local program / script executed by the protocol can simply call something like:

#!/bin/bash
curl "http://servername/unlockThisRequest.php?req=$1"

after it finished.

---

As i just said this works, but it's anything else than nice (congratulations if you kept track of those instructions)

I'd rather prefered a more simple way and (important) this also may cause security issues with the lockThisRequest.php and unlockThisRequest.php files!

I'm fine with this solution, because i'm only using it on a password protected private page. But if you plan to use it on a public or non protected page, you may want to add some security to the php files.

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Anyways, the solution works for me now, but if anyone finds a better way to do it - for example by using ajax requests - he/she would be very welcome to add that way to the respective stackoverflow-documentation or the like and post a link to it on this thread. I'd still be interested in alternative solutions :)

Answer 2

Since this isn't really an expected use of window.location I would doubt that there's an easy way. My recommendation would be to use an AJAX request and have the c++ program send a response when it's done. That way, whatever code needs to run after the c++ program can be run when the request completes.