First Steps — Convert XUL to HTML(GSoC 17)

This summer I am working on a Thunderbird project — Convert XUL to HTML, as a Google Summer of Code 2017 candidate. I am really excited and thrilled to start my journey at Mozilla. I will be working on Mozilla Calendar add-on for Thunderbird aka Lightning. The goal of this project will be to convert XUL dialog boxes into their React versions.

Project Abstract:

Lightning has traditionally been using XUL for its user interface. To modernize, we would like to convert dialogs, tab content and other parts of the user interface to HTML. The new components should use web standards as much as possible, avoiding extensive use of third party libraries.

The second week of the coding period is going to end and there is a lot to tell about the progress of the Convert XUL to HTML project. I was able to setup a balanced development environment and convert a dialog into React. Things are going well so far as the time invested in setting up the development environment is bringing results.
I will start by telling a bit about the challenges that I faced and later a bit about the solutions that I sorted out. Since Thunderbird doesn’t have any extra build step, it was very clear from the start that anything that needs an extra build/compile step is a NO for this project. By that, it means I have to compromise on the awesome features like hot-reloading, jsx etc. that are often paired with React. Another minor issue that I faced was styling of components of dialog box so that they can look exactly like their XUL versions.
At first, I thought of going with the option of importing react, react-dom via script tags and write code without jsx in vanilla js but later I thought why not automate this difficulty. I setup Babel with react-preset and wrote few lines of code to make a clean npm environment to do all these things. Since running Babel on the source directory only outputted the js files, I wrote a few gulp tasks to copy the HTML and CSS files to the compiled js directory.
It is kind of annoying to copy each file manually so I opted for going with Gulp. I also wrote a bash script that removes the Babel scripts and edits the type of main javascript files in the compiled directory’s HTML files. Now there is no extraneous code into the files of compiled directory(dist).
Using Gulp, I can live reload the browser automatically whenever I make any changes to the source files, this is not as good as hot-reloading but it’s better to have it rather than manually hitting the refresh button.
As a web developer, I never worried about the default styling of the browser but for this project, I have to be totally dependent on Firefox toolkit themes and Thunderbird CSS skins. It started to make sense after a few hours of work and now I can create exactly the same layout and appearance of elements in React as it has in XUL dialog boxes. All thanks go to developer tools of Thunderbird and DXR.
The dialog that I and my mentor Philipp decided to do first was calendar-properties-dialog as it was simple and it would help me to get a comfortable start. This dialog is now completely done except a few OS specific CSS rules which can be done later on after testing the dialog in Thunderbird. Working on this dialog was fun and easy and I hope this fun and easiness continues.
Anyone can check the progress of the project by either checking out this repository or logging on to I have also created an iframe testing ground where a user can send and modify the state object of dialog and open the dialog in an iframe. This page uses the same HTML5 postMessage API for communication between iframe and parent as it will use in Thunderbird dialog boxes, similar to how it is already working for the event dialog in the past GSoC project. I am sure the testing ground will save a lot of time in debugging and it clearly shows how things are going on internally within dialog box. It is like a mini control dashboard for our dialog boxes.

Iframe Testing Ground

We haven’t tested out the current react dialog box in Thunderbird yet but after integrating react version of dialog boxes into Thunderbird, we will most likely not be using all these tools to generate the code, but focusing on using the minimal tools available in the Mozilla build system. We would like to hear the suggestions of Mozilla devtools folks to see if they have plans on improving tooling support and possibly using jsx, as it is much easier to read than having that converted to javascript.
I am very excited for the next weeks and I hope things go well as it has been going on. Many thanks to my mentor Philipp for his continuous support and Mozilla community for answering my questions on IRC. Any pieces of advice, suggestion and perhaps encouraging words are always welcome :)