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Contributing to GemRB

First off, thanks for taking the time to contribute!

GemRB is a community driven Free/Libre Open Source Software project that welcomes all. It would not be possible without the help of hundreds of volunteers like you, so everyone is encouraged to contribute, be it code, knowledge, fun or something else!

This file is a non-exhaustive set of soft guidelines and ideas for contributing to GemRB.

Please stay friendly and constructive, we are not robots. I promise.

Where to start?


If you don't trust your skills, take a look at the good first issue subset of reports, ranging from trivial to simple.

Instructions on building and IDE setup can be found in INSTALL or the online developer docs.

If you don't know what to work on:

  • try playing a game with GemRB and make note of any bugs, annoyances or missing features ... then report and fix them,
  • check the list on the bugtracker,
  • check the Roadmap to see what priorities we are currently working on,
  • check out the FIXMEs and TODOs spread throughout the code,
  • write one of the missing file format plugins (doesn't require any game!),
  • pick some of the janitorial tasks (eg. refactoring),
  • ask either on the forums or chat.

You can also help by:

If you're a web developer, check the website reports.

Modders, game designers and artists

  1. GemRB comes with a bundled demo, but it is short. The challenge is to enhance it, but a lot of (compatibly licensed) art is missing. Check the current progress tracker. See also the docs on creating a new game

  2. Some GemRB mods are in the gemrb-mods repo. The mod idea page also lists several ideas from simple tweaks to more complex mods. If you know WeiDU, a good task would be to add more of the documented tweaks (idea page) to gemrb-tweakpack.

  3. Modders can also contribute with research (see above), especially when it requires WeiDU test mods.

Everyone else

The easiest way for you to contribute is to take GemRB for a spin and report problems, omissions, bugs and wishes on the tracker.

Some of the biggest progress has been made when power users tested features in great detail, comparing the original with GemRB behaviour. The games and their engines are complex, so programmers alone can't figure everything out. You can help out by sharing your knowledge in existing reports on the tracker.

Take an active part in the GemRB and Gibberlings3 communities, helping other users, proposing ideas and representing our "colours".

You can help spread the word about the project outside the main channels. Try to bring in new contributors, blog, vlog (Let's Play?), social media posts, organize an event, write a song or other undefined creative approaches.

You can write, film or sing documentation, whether it is included with the project (eg. website, this file) or not (forum, youtube ...).

Let us know of any articles, buzz or other materials you find about GemRB.

You can suggest cool screenshots or fanart for the gallery and videos for the video playlist.

If you're a web designer, check the website repo and suggest improvements.

And finally, do what you want, as long as it is beneficial to the project. :)

But I am completely new to open source, git and GitHub!!

Worry not and check these resources:

Contributing to Free Software and open source projects can be a life changing experience. And it should be fun, so if you find any of this hard to figure out, let us know so we can improve our process and documentation!

Axioms of Style

  1. When in doubt, follow the style of the existing function or file.
    • When creating a new file, follow the style of existing files, pe. Game.h/.cpp.
      • Do not forget to include the license header.
  2. Code indentation is done with single tabulators.
  3. Spaces around operators (foo += bar;).
  4. Try to avoid creating very long lines. There is no set maximum.
  5. Sort includes by type (module, project, system) and alphabetically.

Useful links

Useful tools

  • gdb / admin/run.gdb

You can use the following to automatically run gemrb and already start with a breakpoint in abort():

gdb -q -iex "set breakpoint pending on" -iex "b abort" -ex run --args path/to/gemrb -c agame.cfg
  • valgrind / admin/run.valgrind

We bundle a suppression file for upstream problems at testing/python.supp. You can use it for example this way (if running from the build dir):

valgrind --track-origins=yes --suppressions=../testing/python.supp gemrb/gemrb -c agame.cfg &> valgrind.log
  • git diff display for IE binary formats

Check out admin/enable-ie-git-diff if you want git log and others to be able to display diffs of included binary files (spells and other overrides).

  • make test will run the core test suite if you built with googletest installed

Version tracking

  1. Split your changes (commits) into well-rounded units of logic (git commit -p can help).
  2. Read the commit diff to verify you're commiting what you think. That indentation matches and that no extraneous changes are included (eg. random style changes from bad IDE settings).
  3. Each commit should compile and run. You can do quick fixups with git commit --amend -p.
  4. Commit messages should be descriptive (why is more important than what, include area/creature/script names if possible).
  5. Rebasing and force pushing to pull request branches is fine.

All of this makes reviewing and bisecting for regressions easier.

For maintainers

  1. Squash merge only if the history is a mess or it makes more sense (eg. consecutive commits through the github website).
  2. For release planning check the milestones and any pending pull requests. 2.1. When starting the final approach, use admin/github_release.checklist as a template to track progress in a dedicated issue.
  3. Releases are usually made when larger pieces of work land or many smaller fixes have accrued.
  4. Versioning is semantic, but also ad-hoc. We want 1.0 to be the classic polished release (feature complete or not), so we won't reach it until we implement full iwd2 playability (you can finish the game). Until then, we'll be bumping the patchlevel version number.

Development priorities

The project has roughly two main priorities:

  1. Fixing the known bugs and adding missing features

This is mainly what is on the bug tracker(s), most of the time not requiring invasive changes.

  1. Finishing larger missing pieces

This is represented by the "big picture" problems that remain to be solved. It includes the End of all rewrites milestone, the bigger PST bugs on the tracker, deciding what to do with the incomplete OpenGL renderers and so on.

Generally each release tackles at least one item from #2 and a bag-of-holding worth of #1.


As noted in the previous section, most releases don't have very specific goals. You can check what we're working towards in the current release by reading the NEWS file and, as far as bugtracker backlog goes, by looking at the version's milestone.

The plan for 0.9.4 is to work on iwd2 completability, annoying pst oddities, deal with some postponed issues, and whatever piques the contributor's fancy.

We're looking for ninjas to help with python porting, a SDL_ttf backend, GLESv2 support (no hw, see #938) and a full-fledged installer for windows #612.