Listener to change url before loading it on Mozilla SDK

Question

I'm trying to get something similar to a typo correction for the location bar on mozilla sdk. The user inputs a url on the locationbar and it gets changed before it is loaded. I've tried:

sdk/pagemod as seen here. The problem is it runs when the page starts rendering, not before it starts downloading it.

sdk/tabs => It doesn't have a event that gets called before it starts loading a website.

Above is what I've found that would catch websites the user is trying to enter into. I have also found sdk/system/events, but the only event I found I could use is http-on-modify-request, this does catch every http request. The problem is, you can't modify the url of that request.

To solve this I've seen 2 options:

This addon's way => Get the current tab and load there the new url. The problem is clear, the request may not be from a url the user is trying to load, but from a url inside a page's html. I tried comparing the request url to tabs.activeTab.url, but it gets set after the http-on-modify-request event is sent.

or the solution explained here that I am not sure could work (it is not for mozilla sdk).

So basically my problem right now could be solved with:

-a way to capture the url from the location bar before it starts loading & changing it (I haven't seen anything for this on the sdk) or -a way to know when a request corresponds to a website the user is trying to load in the location bar or -a way to modify the request (url)

Answer 1

I do that in my add-on Google Redirects Fixer which source code you can see here.

Basically, what you're looking for is listening to the http-on-modify-request event. If you follow that code you'll see how to intercept the request and, under certain conditions, abort it and replace it with a new request.

Hope it helps.

Answer 2

"sdk/pagemod as seen here. The problem is it runs when the page starts rendering, not before it starts downloading it."

You can tell it to attach before any content is loaded with contentScriptWhen: start.

Load content scripts immediately after the document element is inserted into the DOM, but before the DOM content itself has been loaded