Sunday, August 26, 2012

GWT Chrome extension using version 2 manifest

Hi everyone,

A while ago I wrote a small post about how to create Chrome extension using GWT, claiming
you could use GWT to make powerful Chrome extension.
One of the comments was regarding the usage of the manifest version.
When you write a Chrome extension, you must provide with a file called manifest.json which
serves as some kind of descriptor file to your extension.
It contains all sorts of things, such as the name of the extension, description, icon, action,
javascript files involved, and so on...

One of the entries in that file is the version entry.
As for today Chrome supports the current version - 2, and also supports (for the moment)
version 1.
However, this is changing, and Google already announced that they will stop supporting version 1
in the future (see, due
to security reasons.

So I was asked whether it was possible or how is it possible to deploy the GWT extension with the
version 2 attribute in the manifest.json file.

Version 2, is stricter in terms of security than version 1. Especially when it comes to using external JavaScript files.
You can read about security concerns over here:

One of the problems I faced, was the inline scripting I had (JavaScript showing inside the HTML).
That problem came not only on my "Hosting" HTML file, but also on the compiled outputs of GWT,
where HTML file which was needed was created and contained JavaScript code.
When that happened, I couldn't execute the extension on Chrome using version 2 in the manifest.json file.

I wrote in response to a comment someone left regarding this problem, that in case Google would have a way to separate JavaScript files from HTML, then problems would be solved.
Back then, I didn't see such options for the GWT compiler.

However, after doing some more searching, I found out that it does exist (!).
And so by adding a simple line in the .gwt.xml file of the application, you can compile all
your GWT application output into a single JavaScript file. Meaning - no HTML files containing
inline JavaScripts.

The line one needs to add is:
<add-linker name="sso" />

I added it to my Quickpik.gwt.xml file, and so when you run the GWT compiler, you get at the end
one JavaScript file containing the entire code of your app. Awesome!

You can access the entire code on Github and download it from there:

You can simply click on the "Downloads" on the right hand of the screen, in order to download
the repository as a ZIP file.

In case you're a GIT user, my suggestion is that you just clone the repository. It's really small.
Simply open your GIT shell and type:
git clone

The extension is already ready to be used in Chrome, and you can deploy it by opening Chrome's
Tools -> Extensions tab, and checking the "Developer mode" box.
Afterwards, you will be able to deploy the extension by selecting the "Load unpacked extension..."
option and selecting the war directory of Quickpik.

I am hoping this is somewhat useful.
I think GWT is an absolutely great tool, and one that can be a lot of fun writing Chrome Extensions.

Until next time!