Browser Helper Object (BHO) for Firefox, Chrome and Safari

I have a working Browser Helper Object (BHO) which is essentially an ATL based COM component. When the component is registered as a BHO in the Registry, the internet 开发者_StackOverflowexplorer calls the SetSite() method passing an object with an interface of IWebBrowser and it also exposes a set of events that can subscribed to - such as OnDocumentComplete, which gives us access to the InnerHTML.

I'm looking for something in the same lines for non IE browsers Firefox, Chrome and Safari. I know firefox extensions is where I should start

• Is it possible to achieve the same using a cross browser SDK like NPAPI ? (Because each browser has its own SDK and extension development platform like cocoa, Pepper API etc. and in addtion most of them support NPAPI.)

• How can I subscribe for events so that a SetSite() sort of function could be called by the browser when the user navigates to a different site ?

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The answer to your first question is simple: no, it is not possible to do this with npapi. See http://npapi.com/extensions for more information about the difference between a Plugin (NPAPI) and an Extension. If there are things you can't do with the extension that you need to do (for example, that require C++ code to work) you could put those things in a NPAPI plugin and use it from your extension. If you decide to go that route I recommend looking at FireBreath.

As to the second, it will differ based on which browser you're writing the extension for; yes, it will need to be different for each browser. A quick google search for "firefox extension event page load" yielded a useful-looking doc.