# Contributing guidelines

Contributions are welcome!

## Big changes

Please open a new issue to discuss or propose a major change. Not only is it fun to discuss big ideas, but we might save each other’s time too. Perhaps some of the work you’re contemplating is already half-done in a development branch.

## Code style: Python

We use `ruff` to format code and imports. The settings for this program are in `pyproject.toml` and `setup.cfg`. Pull requests should follow `ruff` code style.

## Code style: C++

The file `.clang-format` contains our C++ format based on Clang’s formatter, imperfect as it is. We eagerly await a dangling parenthesis (https://reviews.llvm.org/D33029).

In general we prefer to make our C++ look similar to Python PEP8, within reason, because our code is primarily a Python binding. That is, variable and method names are snake_case, class names are CamelCase. Our coding conventions are closer to pybind11’s than qpdf’s. When a C++ object wraps is a Python object, it should follow the Python naming conventions for that type of object, e.g. `auto Decimal = py::module_::import("decimal").attr("Decimal")` for a reference to the Python `Decimal` class even though it is a C++ object.

We don’t like the traditional C++ .cpp/.h separation that results in a lot of repetition. Headers that are included by only one .cpp can contain a complete class, and get the `-inl.h` suffix, unless multiple inclusion is required. Where possible, combined the C++ interface and implementation in a single .cpp or `-inl.h` file. For classes that actually provide an interface used by multiple translation units, a full header is necessary.

Use RAII. Avoid naked pointers. Use the STL, use `std::string` instead of `char *`. Use `#pragma once` as a header guard rather than silly `#ifdef`; they have been around for 25 years.

## Adding C++ code

Where possible, we implement features in Python, unless qpdf provides them.

## Tests

New features should come with tests that confirm their correctness.

## New dependencies

If you are proposing a change that will require a new dependency, we prefer dependencies that are already packaged by Debian or Red Hat. This makes life much easier for our downstream package maintainers.

Dependencies must also be compatible with the source code license.

## English style guide

pikepdf is always spelled “pikepdf”, and never capitalized even at the beginning of a sentence.

Periodic allusions to fish are required, and the writer shall be energetic and mildly amusing.

## Known ports/packagers

pikepdf has been ported to many platforms already. If you are interesting in porting to a new platform, check with Repology to see the status of that platform.