ChromeVox (for developers)

ChromeVox is the built-in screen reader on Chrome OS. It was originally developed as a separate extension but now the code lives inside of the Chromium tree and it's built as part of Chrome OS.

NOTE: ChromeVox ships also as an extension on the Chrome webstore. This version of ChromeVox is known as ChromeVox Classic and is loosely related to ChromeVox (on Chrome OS). All references to ChromeVox relate only to ChromeVox on Chrome OS.

To start or stop ChromeVox, press Ctrl+Alt+Z at any time.

Developer Info

Code location: chrome/browser/resources/chromeos/accessibility/chromevox

Ninja target: it's built as part of “chrome”, but you can build and run browser_tests to test it (Chrome OS target only - you must have target_os = “chromeos” in your GN args first).

Developing On Linux

ChromeVox for Chrome OS development is done on Linux.

See ChromeVox on Desktop Linux for more information.

Debugging ChromeVox

There are options available that may assist in debugging ChromeVox. Here are a few use cases.

Feature development

When developing a new feature, it may be helpful to save time by not having to go through a compile cycle. This can be achieved by setting chromevox_compress_js to 0 in chrome/browser/resources/chromeos/accessibility/chromevox/, or by using a debug build.

In a debug build or with chromevox_compress_js off, the unflattened files in the Chrome out directory (e.g. out/Release/resources/chromeos/accessibility/chromevox/). Now you can hack directly on the copy of ChromeVox in out/ and toggle ChromeVox to pick up your changes (via Ctrl+Alt+Z).

Fixing bugs

The easiest way to debug ChromeVox is from an external browser. Start Chrome with this command-line flag:

out/Release/chrome --remote-debugging-port=9222

Now open http://localhost:9222 in a separate instance of the browser, and debug the ChromeVox extension background page from there.

Another option is to use emacs indium (available through M-x package-list-packages).

It also talks to localhost:9222 but integrates more tightly into emacs instead.

Another option is to use the built-in developer console. Go to the ChromeVox options page with Search+Shift+o, o; then, substitute the “options.html” path with “background.html”, and then open up the inspector.

Debugging ChromeOS

To debug ChromeVox in ChromeOS, you need to add the command-line flag to the config file in device under test(DUT) instead of starting chrome from command line.

(dut) $ echo " --remote-debugging-port=9222 " >> /etc/chrome_dev.conf
(dut) $ restart ui

This is also written in Simple Chrome Workflow Doc.

You need to ssh from your development device into your DUT forwarding port 9222 to open ChromeVox extension background page in your dev device, for example

ssh my_crbook -L 3333:localhost:9222

Then open the forwarded port in the development device, http://localhost:3333 in the example.

You may need to remove rootfs verification to write to /etc/chrome_dev.conf.

(dut) $ crossystem dev_boot_signed_only=0
(dut) $ sudo /usr/share/vboot/bin/ --remove_rootfs_verification
(dut) $ reboot

See Chromium OS Doc for more information about removing rootfs verification.

Running tests

Build the browser_tests target. To run lots of tests in parallel, run it like this:

out/Release/browser_tests --test-launcher-jobs=20 --gtest_filter=ChromeVox*

Use a narrower test filter if you only want to run some of the tests. For example, most of the ChromeVox Next tests have “E2E” in them (for “end-to-end”), so to only run those:

out/Release/browser_tests --test-launcher-jobs=20 --gtest_filter="*E2E*"