mitcho Michael 芳貴 Erlewine

Linguist. Fifth year PhD student at MIT.


Posts Tagged ‘JavaScript’

Checking mochitest test coverage

Tuesday, March 22nd, 2011

Firefox Download ButtonOne of the last bugs for Firefox Panorama was bug 625818: “Check Panorama mochitest test suite coverage”. Our automated tests ensure that we do not regress on existing functionality, but it’s only as good as its coverage: how much of the Panorama code base is actually being “hit” through the process of running the test suite.

Panorama went through a pretty rapid development cycle, making it into Firefox 4 which was released today (yay!). Moreover, for a while we were developing outside of mozilla-central, without the regular “patches require tests” requirement. This makes checking its test coverage particularly important.

Check out the final result, the Panorama test coverage report. The good news: our code coverage is 86%! (Some notes on what improvements can be made are in the bug.)

code coverage report

PhiliKON had previously worked on hooking into the JS Debugger service’s interruptHook to test xpcshell tests. I modified this code to run instead in the Mochitest browser chrome tests. This code can be found on the bug.

With this patch applied, I invoked the test suite with the following code: TEST_PATH=browser/base/content/tests/tabview COVERAGE_FILTER="*tabview*" COVERAGE=true make -C obj-ff-dbg mochitest-browser-chrome . That’s a regular mochitest-browser-chrome invocation with the COVERAGE=true flag which turns on code coverage checking, and COVERAGE_FILTER=*tabview* which filters out results from files which don’t have “tabview” in their paths. This creates a file called coverage.json in the working directory of the test suite, meaning, for me, obj-ff-dbg/_tests/testing/mochitest/.

This JSON file is a multidimensional array, with file paths and then line numbers as keys. The file paths here, as best as possible, have been converted into local filesystem paths. PhiliKON built a script which produces beautiful reports based on this output.

A word of warning: running with this JSD interruptHook is ridiculously slow. A number of tests for Panorama are timing-dependent (drag-drop tests, for example), making some of them fail, but that’s okay… as long as it completed not via a timeout, it actually did run through all the code. In order to get this to run through everything with some degree of control, I split up the mochitest tabview suite in to a few chunks. I then took the multiple resulting coverage.json files and passed them into another script, in tools/coverage/, which takes multiple JSON results like this and puts them together into a single JSON file. I then passed this aggregate JSON file to PhiliKON’s wonderful report script and—voila—the Panorama test coverage report! Easy as pie.

Spring is for Speaking: JSConf, WordCamp SF, IACL

Saturday, March 20th, 2010

I recently confirmed three different very exciting speaking gigs which I’ll be doing this spring:


Creating an image-sized iframe overlay with Shadowbox

Wednesday, January 13th, 2010

I recently have been working with the Shadowbox JavaScript library for an upcoming revision to the MIT Edgerton Digital Collections website. Shadowbox is a nice [[Lightbox (JavaScript)|lightbox]] library designed to work with various JavaScript libraries like jQuery, prototype, and mootools with a nice modular design.

Shadowbox is organized around different “players”—one for each kind of media that will be displayed. The library by default comes with players for Flash, HTML fragments, iframes, QuickTime, and Windows Media. Some of these players, like those for images and video, automatically recognize the media size and adjust the lightbox accordingly, while others such as the iframe player can use a set size or can fill the screen. For the Edgerton site, though, we had a need for displaying an iframe but in the dimensions of a set image, so that we could display the image with an overlay. Here are some notes on how to implement a custom player for Shadowbox.


Mashing up the browser in Maine

Saturday, December 19th, 2009

Last week I was invited to give a talk at the TechMaine annual conference in Portland, Maine.

Being a longer time slot than I previously have used to talk about Ubiquity, I decided to dedicate a good portion of the talk to Jetpack. Being outside of Mozilla for the past few months, this gave me an opportunity to get reacquainted with the Jetpack APIs. I myself was impressed by how easy it was to develop a quick Jetpack. I ended up preparing two to live-code during the talk: one called Helvetica which, with one click, replaces all fonts on the current page with Helvetica; and You Are Here which uses an open API from IPinfoDB to display the physical location of the domain you are currently visiting in the status bar. Both are now on the Jetpack Gallery.

Unfortunately there was a bit of a snowstorm leading up to the event, but there was still a nice turnout and I got to meet some fantastic people there. Ken Shoemake of [[slerp]] and [[quaternion]] fame came up to me after my talk and said “the Ubiquity parser reminded me of the dancing bear… it’s less surprising that it works well as that it works at all.” :) I also enjoyed the other great presentations in the technology track, covering the virtues of REST and basic iPhone development.

Mashup the Browser with Ubiquity and Jetpack

The Ubiquity Persistence Project: exploring a persistent Ubiquity in the toolbar

Thursday, August 20th, 2009

It’s often hard to remember Ubiquity’s presence and keystroke without a visual reminder—even I often forget that I could use Ubiquity and end up going to a search engine or using the search bar for some quick lookup task. What if the Ubiquity input were in the toolbar and always visible? How would that affect people’s use of Ubiquity? And what could we make that look like and how would it behave? Today we’re kicking off the Ubiquity Persistence Project, a new Ubiquity initiative to explore what a persistent Ubiquity might look like in the Firefox toolbar.


In order to facilitate this discussion, we created the Persistence tool. With the Persistence tool you can quickly try out new design and interaction ideas, mocking things up with some simple jQuery-powered JavaScript and CSS and see your changes live. The Persistence tool is bundled with our latest Ubiquity beta (install link).

The Ubiquity Persistence Project: exploring a persistent Ubiquity in the toolbar from mitcho on Vimeo.

I just put together a screencast introducing the initiative, demoing the Persistence tool, as well as talking about this project’s relation to the ongoing work on Taskfox. We’ll look forward to your comments and designs! :D

Exploring Command Chaining in Ubiquity: Part 1

Wednesday, August 19th, 2009

Since the dawn of time people have been asking about command chaining in Ubiquity. If you have a translate command and an email command, it would be great to be able to, for example, translate hello to Spanish and email to Juanito. This is what we call command chaining or [[Pipeline_(Unix)|piping]]: in a single complex query, specifying multiple (probably two) actions and using the first’s output as the second’s input.1

Today I hope to cover some of the technical considerations required in implementing command chaining in Ubiquity, and I will follow up soon with a blog post on the linguistic considerations required as well.


  1. We’re going to limit our discussion here to this restriction that the two verbs are not simply two simultaneous commands, but two commands which operate successively on an input, i.e., that it is true piping. This for example rules out input such as google dogs and translate cat to Spanish, as the second command’s execution does not semantically depend on the first’s execution. This (hopefully uncontroversial) decision also affects the linguistic considerations to be made in my next post. 

Performance vs Responsiveness —or— How I Made the Parser Twice As Fast in One Day

Thursday, August 13th, 2009

Since we launched Ubiquity 0.5, the issue of Parser 2 performance has been brought up over and over within the community. By virtue of having a more flexible and localizable design, Parser 2 was expected to be slower than our original parser, but its current implementation felt noticeably—perhaps unnecessarily—slow compared to Parser 1. Parser 2 performance has been identified as one of the blockers for pushing Ubiquity 0.5+ to all of our 0.1.x users, and has thus been one of my recent foci.

The short story:

Inspired by some comments by Blair, yesterday I was able to make significant (roughly 100%) performance gains in Parser 2, resulting in 40-60% faster parses, depending on the query. This change has been committed and will be released as part of our forthcoming minor update, Ubiquity 0.5.4. Yay!


Converting your Ubiquity command to Ubiquity 0.5

Tuesday, July 21st, 2009

Converting your Ubiquity command to Ubiquity 0.5 from mitcho on Vimeo.

This video walks through the process of converting your Ubiquity commands to Ubiquity 0.5 with Parser 2. For more information, please consult the command conversion tutorial.

A Visual Guide to Community Command Localization

Monday, July 13th, 2009

A natural language interface is only “natural” if it’s in your natural language. With this mantra in mind, we’ve been making steady progress on the challenging problem of Ubiquity localization. The first fruit of this research is in the localization of the parser and bundled commands in Ubiquity 0.5. Here today is a visual guide on command localization in Ubiquity and different options we can take in attacking the community command localization problem. (more…)

The (Shiretoko) Revolution Begins Now

Tuesday, June 23rd, 2009

As many of you know, the upcoming Firefox 3.5 was code-named Shiretoko after the [[Shiretoko National Park]] on Japan’s northern island of Hokkaido. The Shiretoko Foundation and Mozilla Japan just launched a very cool open-web-powered promotional website, interFORest, together with a very powerful educational site, I just went to and registered for my own virtual tree to be planted on the virtual Shiretoko Park. This tree banner will keep track of traffic through my site to the interFORest site and will grow this tree accordingly over time. You can then go to and see all the trees growing on the park. With your help, we can grow it into a forest!

If you are reading this through a feed reader or planet, click on the permalink to view the banner embedded below:

Place one of these personalized canvas-powered virtual tree banners on your site to spread the word on Firefox 3.5, the Shiretoko Park and Foundation, and the power of open communities. All the cool kids are doing it. ^^

Ubiquity Localization Update

Friday, June 12th, 2009

As we move closer and closer to shipping a Ubiquity with there is still much work to be done, particularly in the area of localization. In a recent Ubiquity meeting we laid out the explicit localization goals and non-goals of as follows:

  • Goals for 0.5
    • Parser 2 (on by default)
    • underlying support for localization of commands
    • localization of standard feed commands for a few languages
    • Parser 2 language files for those same languages
  • Nongoals for 0.5
    • distribution/sharing of localizations
    • localization of nountypes

The overall goal for this release of Ubiquity is to come up with a format and standard for localization. Localizations in Ubiquity 0.5 will only apply to commands bundled with Ubiquity, and the localization files themselves will be distributed with Ubiquity. In a future release we will tackle the problem of localizations for commands in the wild and truly croud-source1 this process.


  1. Or “cloud-source”… finally a Japanese accent joke that’s semantically stable! 

Ubiquity presentation at Tokyo 2.0

Wednesday, June 10th, 2009


This past Monday I presented at Tokyo 2.0, Japan’s largest bilingual web/tech community. I presented as part of a session on The Web and Language, which I also helped organize. Other presenters included Junji Tomita from goo Labs, Shinjyou Sunao of Knowledge Creation, developers of the Voice Delivery System API, and Chris Salzberg of Global Voices Online on community translation.

I just put together a video of my Ubiquity presentation, mixing the audio recorded live at the presentation together with a screencast of my slides for better visibility. The presentation is 10 minutes long and is bilingual, English and Japanese.

Ubiquity: Command the Web with Language 言葉で操作する Web from mitcho on Vimeo.


Changes to Ubiquity Parser 2 and the Playpen

Friday, June 5th, 2009

Here’s a quick screencast highlighting some of the changes to Parser 2 and the updated Parser 2 Playpen. This video should be particularly useful to people hoping to add their language to Parser 2. It’s also a good reference for Ubiquity core developers.

Changes to Ubiquity Parser 2 + Playpen from mitcho on Vimeo.

All the features covered, as with all Parser 2 features, require that you get the latest Ubiquity code from our Mercurial repository.

Localizing Ubiquity: commands and nountypes

Monday, May 25th, 2009

Now that Parser 2 is in decent shape and a number of parsing problems in different languages have been tackled, the focus has now shifted to coming up with an approach for localizing Ubiquity commands and nountypes. At last week’s weekly Ubiquity meeting we had a great conversation on this subject, which then has continued on the Google group.

I’ve been framing this problem as two subproblems:

  1. What will be the data structure of localized commands/nountypes within Ubiquity?
  2. How do we distribute/share these localizations?

We’ve mostly been discussing the first problem, weighing the merits of unified objects (with different localized text as different JS properties) as opposed to a [[gettext]]-style approach, and noting that our requirements for commands and nountypes may be different. I hope we can discuss the second issue more in the coming week.

Should everything go through the command author? Should localization be centralized through some web tool? Should it be completely distributed like commands currently are? I invite you to join us in this conversation on the Google group. ^^

Start Panic!

Monday, May 11th, 2009

Just saw this nice demo of the a:visited browser history security issue in action. Visit and click “start” to see it in action.

Picture 2.png

Read about how this security hole works here. Hopefully flashy demos like this will bring more attention to this issue.