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CONTRIBUTING.md
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Contributing to librsvg ======================= Thank you for looking in this file! There are different ways of contributing to librsvg, and we appreciate all of them. * [Source repository](#source-repository) * [Reporting bugs](#reporting-bugs) * [Feature requests](#feature-requests) * [Hacking on librsvg](#hacking-on-librsvg) There is a **code of conduct** for contributors to librsvg; please see the file [`code-of-conduct.md`][coc]. ## Source repository Librsvg's main source repository is at gitlab.gnome.org. You can view the web interface here: https://gitlab.gnome.org/GNOME/librsvg Development happens in the master branch. There are also branches for stable releases. Alternatively, you can use the mirror at Github: https://github.com/GNOME/librsvg Note that we don't do bug tracking in the Github mirror; see the next section. If you need to publish a branch, feel free to do it at any publically-accessible Git hosting service, although gitlab.gnome.org makes things easier for the maintainers of librsvg. To work on the source code, you may find the "[Hacking on librsvg](#hacking-on-librsvg)" section helpful. ## Reporting bugs Please report bugs at https://gitlab.gnome.org/GNOME/librsvg/issues If you want to report a rendering bug, or a missing SVG feature, please provide an example SVG file as an attachment to your bug report. It really helps if you can minimize the SVG to only the elements required to reproduce the bug or see the missing feature, but it is not absolutely required. **Please be careful** of publishing SVG images that you don't want other people to see, or images whose copyright does not allow redistribution; the bug tracker is a public resource and attachments are visible to everyone. You can also [browse the existing bugs][bugs-browse]. ### Obtaining debug logs Librsvg can be asked to output debug logs. Set the `RSVG_LOG` environment variable, and then librsvg will print some information to stdout: ``` $ RSVG_LOG=1 some-program-that-uses-librsvg ... debug output goes here ... ``` As of librsvg 2.43.5, there are no options you can set in the `RSVG_LOG` variable; the library just checks whether that environment variable is present or not. ## Feature requests Librsvg aims to be a small and relatively simple SVG rendering library. Currently we do not plan to support scripting, animation, or interactive features like mouse events on SVG elements. However, we *do* aim go provide good support for SVG's graphical features. Please see the "[reporting bugs](#reporting-bugs)" section for information about our bug tracking system; feature requests should be directed there. It is especially helpful if you file bug for a feature request along with a sample SVG file. ## Hacking on librsvg The library's internals are being documented at https://gnome.pages.gitlab.gnome.org/librsvg/doc/rsvg_internals/index.html Please see that documentation for common tasks like adding support for a new CSS property. ### Working on the source Librsvg uses an autotools setup, which is described in detail [in this blog post][blog]. If you need to **add a new source file**, you need to do it in the toplevel [`Makefile.am`][toplevel-makefile]. *Note that this is for both C and Rust sources*, since `make(1)` needs to know when a Rust file changed so it can call `cargo` as appropriate. It is perfectly fine to [ask the maintainer][maintainer] if you have questions about the Autotools setup; it's a tricky bit of machinery, and we are glad to help. Please read the file [`ARCHITECTURE.md`][arch]; this describes the overall flow of the source code, so hopefully it will be easier for you to navigate. ### Taking advantage of Continuous Integration If you fork librsvg in `gitlab.gnome.org` and push commits to your forked version, the Continuous Integration machinery (CI) will run automatically. A little glossary: * ***Continuous Integration (CI)*** - A tireless robot that builds librsvg on every push, and runs various kinds of tests. * ***Pipeline*** - A set of ***jobs*** that may happen on every push. Every pipeline has ***stages*** of things that get run. You can [view recent pipelines](https://gitlab.gnome.org/GNOME/librsvg/pipelines) and examine their status. * ***Stages*** - Each stage runs some kind of test on librsvg, and depends on the previous stages succeeding. We have a *Test* stage that just builds librsvg as quickly as possible and runs its test suite. If that succeeds, then it will go to a *Lint* stage which runs `rustfmt` to ensure that the coding style remains consistent. Finally, there is a `Cross_distro` stage that tries to build/test librsvg on various operating systems and configurations. * ***Jobs*** - You can think of a job as "something that runs in a specific container image, and emits a success/failure result". For example, the `Test` stage runs a job in a fast Fedora container. The `Lint` stage runs `rustfmt` in a Rust-specific container that always contains a recent version of `rustfmt`. Distro-specific jobs run on container images for each distro we support. The default CI pipeline for people's branches is set up to build your branch and to run the test suite and lints. If any tests fail, the pipeline will fail and you can then examine the job's build artifacts. If the lint stage fails, you will have to reindent your code. ***Automating the code formatting:*** You may want to enable a [client-side git hook](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks) to run `rustfmt` before you can commit something; otherwise the `Lint` stage of CI pipelines will fail: 1. `cd librsvg` 1. `mv .git/hooks/pre-commit.sample .git/hooks/pre-commit` 1. Edit `.git/hooks/pre-commit` and put in one of the following commands: * If you want code reformatted automatically, no questions asked: `cargo fmt` ***Note:*** if this actually reformats your code while committing, you'll have to re-stage the new changes and `git commit --amend`. Be careful if you had unstaged changes that got reformatted! * If you want to examine errors if rustfmt doesn't like your indentation, but don't want it to make changes on its own: `cargo fmt --all -- --check` ***Installing rustfmt*** As of 2018/Sep, our continuous integration pipeline assumes the version of rustfmt that is distributed through the nightly channel of [rustup](rustup.rs). You can install it with ``` rustup component add rustfmt-preview --toolchain=nightly ``` ### Test suite Please make sure that the test suite passes with the changes in your branch. The easiest way to run all the tests is to go to librsvg's toplevel directory and run `make check`. This will run both the small unit tests and the black box tests in the `librsvg/tests` directory. If you need to add new tests (you should, for new features, or for things that we weren't testing!), or for additional information on how the test suite works, please see the file [`tests/README.md`][tests-readme]. In addition, the CI machinery will run librsvg's test suite automatically when you push some commits. You can tweak what happens during CI for your branch in the [`.gitlab-ci.yml` file](.gitlab-ci.yml) — for example, if you want to enable distro-specific tests to test things on a system that you don't have. ### Testing changes The most direct way to test a change is to have an example SVG file that exercises the code you want to test. Then you can rebuild librsvg, and run this: ``` cd /src/librsvg libtool --mode=execute ./rsvg-convert -o foo.png foo.svg ``` Then you can view the resulting `foo.png` image. Alternatively, you can use `./rsvg-view-3` for a quick-and-dirty SVG viewer. **Please update the test suite** with a suitable example file once you have things working (or before even writing code, if you like test-driven development), so we can avoid regressions later. The test suite is documented in [`tests/README.md`][tests-readme]. ### Creating a merge request You may create a forked version of librsvg in [GNOME's Gitlab instance][gitlab], or any other publically-accesible Git hosting service. You can register an account there, or log in with your account from other OAuth services. Note that the maintainers of librsvg only get notified about merge requests (or pull requests) if your fork is in [gitlab.gnome.org][gitlab]. For technical reasons, the maintainers of librsvg do not get automatically notified if you submit a pull request through the GNOME mirror in Github. [Please contact the maintainer][maintainer] directly if you have a pull request there or a branch that you would like to contribute. ### Formatting commit messages If a commit fixes a bug, please format its commit message like this: ``` (#123): Don't crash when foo is bar Explanation for why the crash happened, or anything that is not obvious from looking at the diff. https://gitlab.gnome.org/GNOME/librsvg/issues/123 ``` Note the `(#123)` in the first line. This is the line that shows up in single-line git logs, and having the bug number there makes it easier to write the release notes later — one does not have to read all the commit messages to find the ids of fixed bugs. Also, please paste the complete URL to the bug report somewhere in the commit message, so that it's easier to visit when reading the commit logs. Generally, commit messages should summarize *what* you did, and *why*. Think of someone doing `git blame` in the future when trying to figure out how some code works: they will want to see *why* a certain line of source code is there. The commit where that line was introduced should explain it. ### Testing performance-related changes You can use the [rsvg-bench] tool to benchmark librsvg. It lets you run a benchmarking program **on an already-installed librsvg library**. For example, you can ask rsvg-bench to render one or more SVGs hundreds of times in a row, so you can take accurate timings or run a sampling profiler and get enough samples. **Why is rsvg-bench not integrated in librsvg's sources?** Because rsvg-bench depends on the [rsvg-rs] Rust bindings, and these are shipped outside of librsvg. This requires you to first install librsvg, and then compile rsvg-bench. We aim to make this easier in the future. Of course all help is appreciated! ### Included benchmarks The [`rsvg_internals/benches`][benches] directory has a couple of benchmarks for functions related to SVG filter effects. You can run them with `cargo bench`. These benchmarks use the [Criterion] crate, which supports some interesting options to generate plots and such. You can see the [Criterion command line options][criterion-options]. [coc]: code-of-conduct.md [gitlab]: https://gitlab.gnome.org/GNOME/librsvg [bugs-browse]: https://gitlab.gnome.org/GNOME/librsvg/issues [maintainer]: README.md#maintainers [tests-readme]: tests/README.md [blog]: https://people.gnome.org/~federico/blog/librsvg-build-infrastructure.html [toplevel-makefile]: Makefile.am [tests-readme]: tests/README.md [rsvg-bench]: https://gitlab.gnome.org/federico/rsvg-bench [rsvg-rs]: https://github.com/selaux/rsvg-rs [arch]: ARCHITECTURE.md [benches]: rsvg-internals/benches [Criterion]: https://crates.io/crates/criterion [criterion-options]: https://japaric.github.io/criterion.rs/book/user_guide/command_line_options.html