These last days I've tried to create a similar extension for each browser, and this is a little recap of the first differences among them. A page with a full list of differences can be found in the State of the Add-on Developer Union
Firefox
In Firefox there are two options:
- Create the extension using the "classic" way that goes back to the very beginning and provides full access to anything in Firefox, you can customize it in any way that you like.
- Use the new Add-Ons SDK, only for Firefox 4. These ones doesn't require a restart and it's supposed to be future-proof.
In order to create a classic add-on you can get a skeleton using the Add-on Builder . There are lots of info about how to create these extensions and the API that they can use, and to start creating an Add-on the first step is this page to setup the environment. All you need is a text editor, some patience and be careful following the instructions. You can then configure Firefox to load the extension from the disk but when you make changes to the code you'll have to use an extension to force a reload of all the Firefox code or directly restart it; not nice.
To get started building add-ons with the new SDK, check the tutorial.
First problem: You are required to have Python installed.
What?
I'm so tired of projects that say: you have to install this or that or all of these projects just to get started.
What's so special about Python and the SDK environment that can't be done inside Firefox?
Why should I have to keep the list of instructions instead of being able to click on some buttons "Add extension", "Run tests", "Install", "Reload", etc...
Big boo here.
Maybe they want us to use wget instead of Firefox if they think that command line is so nice.
Anyway, I gave it a go in the Mac (I won't bother trying to install python in windows, it has already too many SDKs there for this and that), and so I followed the basic example, while trying at the same time to adjust it to my goal, I add the files, and when I do the "cfx run" then I get a cryptic error "raise ValueError('invalid resource hostname: %s' % name)". WTF? check again that I haven't done anything too weird. Nops. Then put back exactly the sample code. Nops. Search for the message. Bingo!, although there's no warning about this in the tutorial, you CAN'T use uppercase letters in the folder name. Hello Mozilla, it's 2011, I thought that the problems with uppercase and lowercase were gone long ago since MS-DOS. Why aren't your wonderful Python scripts able to deal with them?
Another big fail.
As a summary: I got a bad taste of the Add-ons SDK. When they put forward something that isn't oriented to Python lovers I might test it again (please note that I haven't even tested the API, just the environment makes me go back to keep using the classic method)
Chrome
It seems that there's a lot of work going on here in order to provide a very complete API for the extensions as well as good documentation and lots of examples. You can see a very basic one here and everything is quite easy to follow. Given the fast path that it's set on the release of new Chrome versions we can expect that this trend will continue and that they will add missing features to make some tasks even easier.
The only thing that you need is a text editor and Chrome, and by following the instructions you can get it working. It's not so powerful as the classic extensions in Firefox, but it's really easy to start creating an extension and there are lots of examples to check how they work.
Safari
It seems again that there's plenty of documentation at a central place, but just in the first page there's something strange:
Important: To develop extensions for Safari, you need to sign up for the Safari developer program online, at http://developer.apple.com. You need a signed certificate before your extension can be installed.
Uh?
So to create an sample extension in my own computer I need a certificate?
Ok, this shows again that Apple is a control freak. Why do I have to register to get an Apple ID and then get enrolled into a "Safari developer" program so that I can finally request a signing certificate, just to create a test extension? I can understand that in order to deploy it I might need to sign it, but I really should be able to create an extension for myself without the need to sign two looong agreements with Apple (I'm not sure if there was a paragraph about my first newborn there)
Anyway I go ahead and get a certificate in the Mac, and then it seems to work, but I would like to keep the development environment in Windows, so I try to install the downloaded *.cer there but anyway Safari keeps saying that there's no signing certificate installed. After a little while and some digging I realize that I must export the private signing key from the Mac KeyChain to Windows and once I installed it there Safari started working.
In some regards this might be the simpler interface of all the browsers in order to create an extension as you get a dialog to setup the basic configuration of the extension instead of editing them in a text file. The way that the code is setup is similar to Chrome (and Opera): background pages, injected scripts, so porting from Chrome wasn't a hard task.
As it happens with almost everything Apple does, if you are satisfied with what they offer, they try to make it quite easy, but if you want something extra then it's a no go.
Opera
I started checking the Opera API with the very first builds where they started adding support for extensions. In those days the API wasn't complete, there were a bunch of things that didn't work at all, so due to my hurry to test it I became a little frustrated because there were so many things missing, there was almost no documentation at the moment so it required a lot of effort to try to make something work because the examples were quite basic.
Now they have improved everything a lot, the behavior is similar to Chrome and Safari, but this is still a fresh SDK, so there are still missing features available in other browsers. They have written now lots of documentation and I guess that very shortly it should be quite easy to port an extension between Opera, Chrome and Safari due to the convergence of APIs that the developers find useful.
For the moment Opera it's lacking an API call similar to the ones that I've used for the other browsers so I will put the extension for browser at rest waiting for them to include them instead of struggle again and get tired of finding that it's not possible in any way.
