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CONTRIBUTING.md

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Contributing

RGBDS was created in the late '90s and has received contributions from several developers since then. It wouldn't have been possible to get to this point without their work, and it is always open to the contributions of other people.

Reporting Bugs

Bug reports are essential to improve RGBDS and they are always welcome. If you want to report a bug:

  1. Make sure that there isn't a similar issue already reported.
  2. Figure out a way of reproducing it reliably.
  3. If there is a piece of code that triggers the bug, try to reduce it to the smallest file you can.
  4. Create a new issue.

Of course, it may not always be possible to give an accurate bug report, but it always helps to fix it.

Requesting new features

If you come up with a good idea that could be implemented, you can propose it to be done.

  1. Create a new issue.
  2. Try to be as accurate as possible. Describe what you need and why you need it, maybe with examples.

Please understand that the contributors are doing it in their free time, so simple requests are more likely to catch the interest of a contributor than complicated ones. If you really need something to be done, and you think you can implement it yourself, you can always contribute to RGBDS with your own code.

Contributing code

If you want to contribute with your own code, whether it is to fix a current issue or to add something that nobody had requested, you should first consider if your change is going to be small (and likely to be accepted as-is) or big (and will have to go through some rework).

Big changes will most likely require some discussion, so open an issue and explain what you want to do and how you intend to do it. If you already have a prototype, it's always a good idea to show it. Tests help, too.

If you are going to work on a specific issue that involves a lot of work, it is always a good idea to leave a message, just in case someone else is interested but doesn't know that there's someone working on it.

Note that you must contribute all your changes under the MIT License. If you are just modifying a file, you don't need to do anything (maybe update the copyright years). If you are adding new files, you need to use the SPDX-License-Identifier: MIT header.

  1. Fork this repository.
  2. Checkout the master branch.
  3. Create a new branch to work on. You could still work on master, but it's easier that way.
  4. Compile your changes with make develop instead of just make. This target checks for additional warnings. Your patches shouldn't introduce any new warning (but it may be possible to remove some warning checks if it makes the code much easier).
  5. Test your changes by running ./run-tests.sh in the test directory. (You must run ./fetch-test-deps.sh first; if you forget to, the test suite will fail and remind you mid-way.)
  6. Format your changes according to clang-format, which will reformat the coding style according to our standards defined in .clang-format.
  7. Create a pull request against the branch master.
  8. Be prepared to get some comments about your code and to modify it. Tip: Use git rebase -i origin/master to modify chains of commits.

Adding a test

The test suite is a little ad-hoc, so the way tests work is different for each program being tested.

Feel free to modify how the test scripts work, if the thing you want to test doesn't fit the existing scheme(s).

RGBASM

Each .asm file corresponds to one test. RGBASM will be invoked on the .asm file with all warnings enabled.

If a .out file exists, RGBASM's output (print, println, etc.) must match its contents. If a .err file exists, RGBASM's error output (warn, errors, etc.) must match its contents.

If a .out.bin file exists, the object file will be linked, and the generated ROM truncated to the length of the .out.bin file. After that, the ROM must match the .out.bin file.

RGBLINK

Each .asm file corresponds to one test, or one set of tests.

All tests begin by assembling the .asm file into an object file, which will be linked in various ways depending on the test.

Simple tests

These simply check that RGBLINK's output matches some expected output.

A .out file must exist, and RGBLINK's output must match that file's contents.

Additionally, if a .out.bin file exists, the .gb file generated by RGBLINK must match it.

Linker script tests

These allow applying various linker scripts to the same object file. If one or more .link files exist, whose names start the same as the .asm file, then each of those files correspond to one test.

Each .link linker script must be accompanied by a .out file, and RGBLINK's output must match that file's contents when passed the corresponding linker script.

Variant tests

These allow testing RGBLINK's -d, -t, and -w flags. If one or more -<flag>.out or -no-<flag>.out files exist, then each of them corresponds to one test.

The object file will be linked with and without said flag, respectively; and in each case, RGBLINK's output must match the .out file's contents.

RGBFIX

Each .flags file corresponds to one test. Each one is a text file whose first line contains flags to pass to RGBFIX. (There may be more lines, which will be ignored; they can serve as comments to explain what the test is about.)

RGBFIX will be invoked on the .bin file if it exists, or else on default-input.bin.

If no .err file exists, RGBFIX is simply expected to be able to process the file normally. If one does exist, RGBFIX's return status is ignored, but its output must match the .err file's contents.

Additionally, if a .gb file exists, the output of RGBFIX must match the .gb.

RGBGFX

There are three kinds of test.

Simple tests

Each .png file corresponds to one test. RGBGFX will be invoked on the file. If a .flags file exists, it will be used as part of the RGBGFX invocation (@<file>.flags).

If .out.1bpp, .out.2bpp, .out.pal, .out.tilemap, .out.attrmap, or .out.palmap files exist, RGBGFX will create the corresponding kind of output, which must match the file's contents. Multiple kinds of output may be tested for the same input.

If no .err file exists, RGBGFX is simply expected to be able to process the file normally. If one does exist, RGBGFX's return status is ignored, but its output must match the .err file's contents.

Reverse tests

Each .1bpp or .2bpp file corresponds to one test. RGBGFX will be invoked on the file with -r 1 for reverse mode, then invoked on the output without -r 1. The round-trip output must match the input file's contents. If a .flags file exists, it will be used as part of the RGBGFX invocation (@<file>.flags).

Random seed tests

Each seed*.bin file corresponds to one test. Each one is a binary RNG file which is passed to the rgbgfx_test program.

Downstream projects

  1. Make sure the downstream project supports make <target> RGBDS=<path/to/RGBDS/>. While the test suite supports any Make target name, only Make is currently supported, and the Makefile must support a RGBDS variable to use a non-system RGBDS directory.

    Also, only projects hosted on GitHub are currently supported.

  2. Add the project to test/fetch-test-deps.sh: add a new action line at the bottom, following the existing pattern:

    action  <owner>  <repo>  <date of last commit>  <hash of last commit>

    (The date is used to avoid fetching too much history when cloning the repositories.)

  3. Add the project to test/run-tests.sh: add a new test_downstream line at the bottom, following the existing pattern:

    test_downstream  <owner>  <repo>  <makefile target>  <build file>  <sha1 hash of build file>