Expression based 2D graphics system based on Lucre.
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We'd love for you to contribute to our source code and to improve this project!

Found an Issue?

If you find a bug in the source code or a mistake in the documentation, you can help us by submitting an issue to the project's git Repository. Even better you can submit a Pull Request with a fix.

Please see the Submission Guidelines below.

Submission Guidelines

Submitting an Issue

Before you submit your issue search the archive, maybe your question was already answered.

If your issue appears to be a bug, and hasn't been reported, open a new issue. Help us to maximise the effort we can spend fixing issues and adding new features, by not reporting duplicate issues. Providing the following information will increase the chances of your issue being dealt with quickly:

  • Overview of the Issue - if an error is being thrown a non-minified stack trace helps
  • Motivation for or Use Case - explain why this is a bug for you
  • Project Version(s) - is it a regression?
  • Environment and Operating System - state under which system the problem occurs (OS, Java and Scala version etc.)
  • Reproduce the Error - provide a simple reproducible example or an unambiguous set of steps.
  • Related Issues - has a similar issue been reported before?
  • Suggest a Fix - if you can't fix the bug yourself, perhaps you can point to what might be causing the problem (line of code or commit)

If you get help, help others. That way everyone benefits!

Submitting a Pull Request

Before you submit your pull request consider the following guidelines:

  • Search the git repository for an open or closed Pull Request that relates to your submission. You don't want to duplicate effort.

  • Please sign our Contributor License Agreement (CLA) before sending pull requests. We cannot accept code without this.

  • Make your changes in a new git branch:

    git checkout -b issue-descriptive-name-branch work
  • Create your patch, including appropriate test cases if applicable.

  • Follow our Coding Rules.

  • Run the project's full test suite (if provided) and ensure that all tests pass.

  • Commit your changes using a descriptive commit message that follows our commit message conventions.

    git commit -a

    Note: the optional commit -a command line option will automatically "add" and "rm" edited files.

  • Build your changes locally to ensure all the tests pass (typically sbt clean test).

  • Push your branch to the git hosting service (e.g. GitLab):

    git push origin issue-descriptive-name-branch
  • In the git hosting service (e.g. Codeberg), send a pull request to the upstream work branch, or to main branch if no work branch exists. If you are unsure about which branch to use as reference, consult with us first (through the issue tracker) to determine the best point of merge.

  • If we suggest changes then:

    • Please make the required updates.
    • Re-run the test suite to ensure tests are still passing.
    • Commit your changes to your branch (e.g. issue-descriptive-name-branch).
    • Push the changes to your git repository on the hosting service (this will update your Pull Request).

If the PR gets too outdated we may ask you to rebase and force push to update the PR:

git rebase work -i
git push origin issue-descriptive-name-branch -f

WARNING. Squashing or reverting commits and forced push thereafter may remove comments on code on the git hosting service that were previously made by you and others in your commits.

That's it! Thank you for your contribution!

After your pull request is merged

After your pull request is merged, you can safely delete your branch and pull the changes from the main (upstream) repository:

  • Delete the remote branch on the git hosting service (e.g. Codeberg) either through its web UI or your local shell as follows:

    git push origin --delete issue-descriptive-name-branch
  • Check out the work branch, or if it does not exist, the main branch (or the branch into which your work was merged):

    git checkout work -f
  • Delete the local branch:

    git branch -D issue-descriptive-name-branch
  • Update your work branch (or the branch into which your work was merged) with the latest upstream version:

    git pull --ff upstream work

Coding Rules

To ensure consistency throughout the source code, keep these rules in mind as you are working:

  • All features or bug fixes should be tested by one or more unit tests. For Scala projects, the preferred framework is ScalaTest.
  • All public API methods should be documented (scaladoc for Scala projects, javadoc for Java projects).
  • In general, follow the usual Scala style guide. In particular
    • UTF-8 character encoding
    • two spaces indentation, no tabs
    • line breaks after max 120 characters
    • if you use IntelliJ IDEA, basically you can use the default auto-format of its Scala plugin.

Git Commit Guidelines

Commit Message Format

Use standard practice for the commit message. Use a subject line no longer than 100 characters, followed by a body outlining the details of the commit. If an issue in the issue tracker exists, refer to it (e.g. fixes #1234). You can also link to other commits by using the commit hash.


If the commit reverts a previous commit, it should begin with revert: , followed by the header of the reverted commit. In the body it should say: This reverts commit <hash>., where the hash is the SHA of the commit being reverted.

Signing the CLA

Please sign our Contributor License Agreement (CLA) before sending pull requests. For any code changes to be accepted, the CLA must be signed. It's a quick process, we promise!

This CLA covers all projects at or, so you should have to go through this process only once. Thanks for your understanding.

Further Information

You can find out more detailed information about contributing in the project Sciss/Contributing.