Programming Language Extensions for Energy-Efficient Web
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AutoGreen is a system that automatically annotates (mobile) Web applications to enable energy-efficiency optimizations by the Web runtime. The annotations are called GreenWeb, which are Web language extensions that allow Web developers to express user QoS expectations at an abstract level. Based on programmer-guided QoS information the Web runtime dynamically determines how to deliver the target QoS experience while minimizing the energy consumption.

This is a project from the Electrical and Computer Engineering Department at The University of Texas at Austin. See the contributors and acknowledgement at the end for more information.

Repo Structure

The high-level structure of this repo is as follows:

  • css/: The CSS code of the AutoGreen panel.
  • js/: The JavaScript code of the AutoGreen annotation logic.
  • The script that builds AutoGreen.
  • bookmarklet.html: The bookmark generation page.
  • A simple python-based HTTPS server that can be use to host AutoGreen.
  • The original readme file of Visual Event.
  • This file.

Installation and Usage

Installation AutoGreen works as a browser bookmarklet, which is essentially a piece of JavaScript code that gets injected to the end of a Web application. Install it in following steps:

  • Build the AutoGreen code by sh ./ This will generate AutoGreen code in the out/ directory.
  • (Optional) Supply the c commandline option (i.e., sh ./ c) to compress the JavaScript code in AutoGreen (npm install uglify-js if uglifyjs is not present). Supply the d option for generating JSDoc documentations for AutoGreen (npm install jsdoc if jsdoc is not present). Supply cd for doing both.
  • Host AutoGreen in a HTTPS server because most browsers do not allow injecting code from the local file system to a webpage. The repo checkout contains a simple python-based HTTPS server. To use that simply run python in the repo directory.
  • Open the bookmarklet generation page bookmarklet.html in a Web browser, and drag the AutoGreen link to your bookmark bar. For more details take a look at the code in bookmarklet.html. Otherwise you are all set!

Usage Navigate to the Web application (webpage) that you want to apply GreenWeb annotations to.

  • Click AutoGreen on your browser bookmarklet bar. DOM nodes with JavaScript events will be highlighted.
  • Press key h to display the help page.
  • To annotate an event of a DOM node manually:
    • Move the mouse over any highlighted DOM node to display the AutoGreen box which shows further event details. GreenWeb annotation information (at the bottom of the box) is "Unknown" at this point.
    • Click "trigger event" link on the AutoGreen panel to dispatch the selected event. After the event finishes execution, AutoGreen will automatically update the GreenWeb annotations in the box.
    • Press key q to dump all the annotations identified so far to the console.
  • To annotate all events of all DOM nodes automatically:
    • Press key d which automatically annotates all events and dump the annotations to the console.

How AutoGreen Works

GreenWeb Language Extensions

AutoGreen is a system that automatically annotates Web applications with GreenWeb language extensions. The GreenWeb readme provides a brief introduction to the syntax and sementics of the GreenWeb language extensions. It also describes instructions on how to patch the Chromium browser to support the Greenweb language extensions. Understanding AutoGreen requires some basic knowledge of GreenWeb so we encourage you to take a look at GreenWeb first.

How AutoGreen Applies GreenWeb Annotations

AutoGreen mainly consists of two phases. The first phase is to detect the JavaScript events associated with all DOM nodes in a Web application. The second phase is to detect, and annotate, the QoS information of each event.

For the event detection phase, AutoGreen owes a great debt of gratitude to Visual Event, which automatically identifies the details of all JavaScript events associated with all DOM elements on a Web application (webpage). In fact, AutoGreen started as a fork of Visual Event. Take a look at Visual Event's readme for more details of the event detection phase.

For the QoS detection phase, AutoGreen performs a profiling run of each event by explicitly triggering its callback function. During the callback execution, AutoGreen checks for certain conditions to determine an event’s QoS type as follows. An event’s QoS type is set to “continuous” if its callback function triggers a jQuery animate() function, a rAF, or a CSS transition/animation. Otherwise the QoS type is set to “single.”

  • To detect animate() and rAF, we overload their original functions and check in the overloaded function.
  • To detect CSS transition/animation, we register a transitionend/animationend event, which if triggered indicates that a CSS transition/animation exists.

As a proof-of-concept prototype, our current implementation does not yet support checking other ways of realizing animations, but could be trivially extended to do so by following a similar detection procedure as described above.

Contributors and Acknowledgments

AutoGreen (and GreenWeb) is developed by Yuhao Zhu at UT Austin. The project is advised by Vijay Janapa Reddi.

AutoGreen owes a great debt of gratitude to Visual Event and its author Allan Jardine.


AutoGreen is under the GPL v2 license. In short, this means AutoGreen is free software that can be redistributed and modified in any way, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

The GPL v2 license does NOT require the modified version to be released. But if one releases the modified version to the public in some way, the GPL requires you to make the modified source code available under the GPL.