Pixman

Pixman is a library that provides low-level pixel manipulation features such as image compositing and trapezoid rasterization.

Questions should be directed to the pixman mailing list.

You can also file bugs on the Issues page or submit improvements in form of a Merge Request.

For real time discussions about pixman, feel free to join the IRC channels #cairo and #xorg-devel on the OFTC IRC network.

Contributing

In order to contribute to pixman, you will need a working knowledge of the git version control system. For a quick getting started guide, there is the Everyday Git With 20 Commands Or So guide from the Git homepage. For more in-depth git documentation, see the resources on the Git documentation page.

Pixman uses the infrastructure from the freedesktop.org umbrella project. For instructions about the git service on freedesktop.org, see the Git Infrastructure wiki page.

The Pixman master repository can be found at: https://gitlab.freedesktop.org/pixman/pixman

Sending patches

Patches should be submitted in form of Merge Requests via GitLab.

You will first need to verify your freedesktop.org account by creating a User verification issue.

Make sure to add ssh keys to your GitLab profile.

Then you will be able to create a fork of the main pixman repository via the Fork button on the top right. Once that is done you can add your personal repository as a git remote to your local pixman development git repository:

$ git remote add my-gitlab git@ssh.gitlab.freedesktop.org:YOURUSERNAME/pixman.git
$ git fetch my-gitlab

Once that is set up, the general workflow for sending patches is to create a new local branch with your improvements and once it's ready push it to your personal pixman fork:

$ git checkout -b fix-some-bug
...
$ git push my-gitlab

The output of the git push command will include a link that allows you to create a Merge Request against the official pixman repository.

Whenever you make changes to your branch (add new commits or fix up commits) you push them back to your personal pixman fork:

$ git push -f my-gitlab

If there is an open Merge Request GitLab will automatically pick up the changes from your branch and pixman developers can review them anew.

In order for your patches to be accepted, please consider the following guidelines:

• At each point in the series, pixman should compile and the test suite should pass.

  The exception here is if you are changing the test suite to demonstrate a bug. In this case, make one commit that makes the test suite fail due to the bug, and then another commit that fixes the bug.

  You can run the test suite with

  $ meson test -C builddir

  It will take around two minutes to run on a modern PC.

• Follow the coding style described in the CODING_STYLE file. The coding style rules are also reflected in the clang-format configuration, so you could use autoformatting from your IDE (if it supports clang-format) or invoke it manually with:

  $ clang-format -i pixman/file-to-check.c

• For bug fixes, include an update to the test suite to make sure the bug doesn't reappear.

• For new features, add tests of the feature to the test suite. Also, add a program demonstrating the new feature to the demos/ directory.

• Write descriptive commit messages. Useful information to include: - Benchmark results, before and after

  • Description of the bug that was fixed
  • Detailed rationale for any new API
  • Alternative approaches that were rejected (and why they don't work)
  • If review comments were incorporated, a brief version history describing what those changes were.

• For big patch series, write an introductory post with an overall description of the patch series, including benchmarks and motivation. Each commit message should still be descriptive and include enough information to understand why this particular commit was necessary.

Pixman has high standards for code quality and so almost everybody should expect to have the first versions of their patches rejected.

If you think that the reviewers are wrong about something, or that the guidelines above are wrong, feel free to discuss the issue. The purpose of the guidelines and code review is to ensure high code quality; it is not an exercise in compliance.