Contributing Code


  • Whether you‘re writing a new feature or fixing an existing bug, it pays to get a second opinion before you get too far. If it’s a new feature idea, post to the discussion group (angleproject).
  • Not all bugs in our bug system are assigned, but if the one you‘re interested in fixing is, send a note to the person it’s assigned to and ask if they would like a patch.
  • Behavior changes and anything nontrivial (i.e. anything other than simple cleanups and style fixes) should generally be tracked in the bug system. Please file a bug and describe what you‘re doing if there isn’t one already.
  • If you would like bug-editing rights, simply ask a team member via email or the discussion group.

Get your code ready


  1. Must conform to the ANGLE style guidelines.
  2. Must be tested. (see the Testing section below)
  3. Should be a reasonable size to review. Giant patches are unlikely to get reviewed quickly.

Build maintenance

  1. If you added or removed source files:
  2. ANGLE‘s script is used by Chromium's gn build. If you change build files other than to add or remove source files be aware you could break the Chromium build. ANGLE’s commit queue (CQ) will detect such breakage. Ask a project member for help with Chromium issues if you don't have a Chromium checkout.
  3. Some generated code is baked into the repository. If you modify the source of these files, such as the translator's glslang.l, or one of the internal shaders in the Vulkan backend, you will need to run scripts/ and include the autogenerated files in your change. git cl upload should warn you if you are missing this step.


  • ANGLE uses trybots to test on a variety of platforms. Please run your changes against our bots and check the results before landing changes or requesting reviews.
    • Upload your change (see Making changes).
    • To kick off a try job, use the ‘CQ Dry Run’ button, or set the Commit-Queue +1 label to trigger a dry run of the CQ (will not land the change).
    • If you are not part of the angle-committers group, you will need to either ask to be added or ask a member of the group to submit the tryjob for you. Add syoussefi or geofflang as a reviewer for assistance.
    • Wait for the bots to report the result on the code review page. The bot results should be visible in Gerrit as yellow (in-progress), green (passed), or red (failed). This can take up to two hours for some of the debug bots. Click on the colored rectangle to open the bot log to triage failed tests.
    • If a failure is unexpected, or seems likely unrelated to your change, ask an ANGLE project member for advice.
    • We do not currently have the capability to run individual bots or tests in a run.
  • Tests can also be run locally, ANGLE's main testing methods are:
    • angle_unittests, angle_end2end_tests and angle_white_box_tests targets.
    • The OpenGL CTS also known as drawElements Quality Program (dEQP). If you're working on a new feature, there may be some extensive tests for it already written.
    • The Top-of-Tree WebGL Conformance tests.
      • If you are a Chromium developer, see Building ANGLE for Chromium Development for instructions on building ANGLE within Chromium.
      • If you aren't a browser developer, you should be able to drop your compiled DLLs into a Chrome installation, in place of those distributed with Chrome, to check WebGL conformance. Chrome Canary is well-suited for this.
    • If your code isn‘t covered by an existing test, you are strongly encouraged to add new test coverage. This both ensures that your code is correct and that new contributors won’t break it in the future.
    • Add new tests to angle_end2end_tests for OpenGL-based API tests, angle_unittests for cross-platform internal tests, and angle_white_box_tests for rendering tests which also need visibility into internal ANGLE classes.
    • If you are submitting a performance fix, test your code with angle_perftests and add a new performance test if it is not covered by the existing benchmarks. For more documentation on angle_perftests see the README.
    • The Chromium GPU FYI bot waterfall provides continuous integration for ANGLE patches that have been committed. There may be hardware configurations that are not tested by the ANGLE trybots, if you notice breakage on this waterfall after landing a patch, please notify a project member.


  1. You must complete the Individual Contributor License Agreement. You can do this online, and it only takes a minute. If you are contributing on behalf of a corporation, you must fill out the Corporate Contributor License Agreement and send it to Google as described on that page.
  2. Once you've submitted the CLA, please email the following information (as entered on the CLA) to geofflang at chromium dot org for record keeping purposes:
    • Full Name:
    • Email:
    • Company (If applicable):
  3. If you‘ve never submitted code before, you must add your (or your organization’s) name and contact info to the AUTHORS file.
  4. NOTE TO REVIEWERS: Follow the External Contributor Checklist.

Life of a Change List

Getting started with Gerrit for ANGLE

  1. Go to
  2. Log in with the email you use for your git commits.
  3. Follow the directions on the new-password page to set up authentication with your Google account.
  4. Make sure to set your real name.
  5. Check out the repository (see DevSetup).
  6. Install the Gerrit commit_msg hook
    • Gerrit requires a hook to append a change ID tag to each commit, so that it can associate your CL with a particular review, and track dependencies between commits.
    • Download the hook from and copy this file to .git/hooks/commit-msg within your local repository. On non-Windows platforms, ensure that permissions are set to allow execution.
    • BE AWARE: Some patch management tools, such as StGit, currently bypass git hooks. They should not currently be used with changes intended for review.

Making changes

  1. Commit your changes locally:
    • git add src/../FileName.cpp
    • git commit
    • A text editor will open. Add a description at the top of the file.
    • Associate the CL with an issue in the issue tracker (e.g. a fix for a reported bug) by adding the following line to the commit message: Bug: angleproject:<issue number>.
    • Save.
    • Close the text editor.
    • Use git commit --amend to update your CL with new changes.
    • Use git cl format to amend the style of your CL. This saves both your time and the reviewers'!
  2. Ensure your code is landed on top of latest changes
    • git pull --rebase
    • Resolve conflicts if necessary
  3. Upload the change list
    • git cl upload
    • The change list and modified files will be uploaded to ANGLE Gerrit.
    • Follow the generated URL to the new issue.
    • Take a moment to perform a self-review of your code. Gerrit's viewer makes it easy to see whitespace errors, erroneous tabs, and other simple style problems.
    • Select reviewers. If you don‘t do this, reviewers may not realize you’re requesting a review!
    • Make changes, upload and repeat as necessary.
    • Project members and others will review your code as described in the CodeReviewProcess.
  4. If your change list needs revision:
    • If you have correctly installed the commit hook from the section above, Gerrit will be able to track your changes by Change-Id.
    • You should need only to update your commit with git commit --amend and re-upload with git cl upload.
  5. Landing change after it receives +2 Code Review:
    • If you are a committer, you may submit the change yourself via the Gerrit web interface.
    • If you are not a committer, ask your reviewer to submit the change list.
  6. Pull and integrate reviewed CL:
    • git pull --rebase

Selecting reviewers

When your CL is ready to review, you can use the “Find Owners” button in Gerrit to select appropriate code reviewers. They will be able to route your CL to additional reviewers as neccessary and answer any questions you may have about the process.

Rules for submission

  • At least one Owner must give approval.
  • The owner must be from the most specific directory.
  • At least two Committers must give approval for non-trival CLs. For trivial CLs, a single Owner approval is sufficient.
  • Only Committers may submit CLs. If you aren't a committer please ask for help submitting.
  • Committers may submit high-priority small CLs immediately using TBR. See the Chromium docs for more info.
  • There are exceptions to these rules. Use your best judgement.

Reverting a CL

Sometimes a change will cause an unforseen problem, e.g. on a platform that's not tested with pre-submit testing. In those cases, a CL may be reverted; often by a “Wrangler”, who is an engineer who keeps the testing infrastructure healthy/green.

The best and easiest way to create a revert change is with Gerrit‘s REVERT button, in the upper-right corner of the original change. Pressing this will pop up a dialog with a template commit message, and an optional checkbox for automatically sending the revert CL to CQ. Please edit the commit message with the reason for the revert. When satisfied, press the dialog’s REVERT button. It is wise to add the author and reviewers of the original CL as reviewers of the revert CL. If it's been less than 24 hours since the original CL landed, the revert Cl will land immediately and bypass the try bots.

If you cannot use Gerrit's REVERT button, you can create a revert CL with the “git revert” command. When doing so, the commit message should include a short description for why the original commit needs to be reverted, and potentially a bug; similar to this example revert CL.

Relanding a reverted CL

When you re-land a reverted CL, follow this process:

  • Prefix the CL title with "Reland: ".
  • Keep the commit message of the original CL and add a description of what changed in the re-land.
  • Ensure the re-land CL has a unique Change-Id.
  • First upload the reverted CL as Patchset 1 with no changes applied.
  • Then, apply your fixes, and upload your CL as a new Patchset. The reviewers will be able to see the diff between Patchset 1 and the fixed/final Patchset.

Here is an example reland CL. This link shows the difference between Patchset 1 and the fixed/final Patchset. Notice how a reviewer can easily see the fix to the original CL.

If you do not need to make any changes to your CL to re-land, you can instead use Gerrit's CREATE RELAND button.

Committer status

Similar to Chromium's committer status, long-term contributors to the ANGLE project may request to join the angle-committers group. This allows you to give +2 on code reviews and land patches without assistance. After about 6 months of regular contributions, you may request committer status from a core ANGLE team member via email or code review. Chromium committers and Googlers may ask at any time.

OWNERS files and becoming an Owner

See these Chromium docs for some good guidelines: link.

More info

See also: