README

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:

    https://lists.freedesktop.org/mailman/listinfo/pixman

You can also file bugs at

    https://gitlab.freedesktop.org/pixman/pixman/-/issues/new

or submit improvements in form of a Merge Request via

    https://gitlab.freedesktop.org/pixman/pixman/-/merge_requests

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

    https://www.kernel.org/pub/software/scm/git/docs/everyday.html

from the Git homepage. For more in depth git documentation, see the
resources on the Git community documentation page:

    https://git-scm.com/documentation

Pixman uses the infrastructure from the freedesktop.org umbrella
project. For instructions about how to use the git service on
freedesktop.org, see:

    https://www.freedesktop.org/wiki/Infrastructure/git/Developers

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 create a fork of the main pixman repository at

    https://gitlab.freedesktop.org/pixman/pixman

via the Fork button on the top right. Once that is done you can add your
personal repository as a remote to your local pixman development git checkout:

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

    git fetch my-gitlab

Make sure to have added ssh keys to your gitlab profile at

    https://gitlab.freedesktop.org/profile/keys

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 

        make check

   if you built pixman with autotools or

       meson test -C builddir

   if you built pixman with meson.

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

 - Follow the coding style described in the CODING_STYLE file

 - 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.