# Contributing to ltk

Thanks for considering a contribution. This document covers the practical
mechanics: how to set up your environment, how to run tests, what shape a
patch should take, and where to send it.

For background on the toolkit itself, read
[`docs/onboarding.md`](docs/onboarding.md) and
[`docs/architecture.md`](docs/architecture.md) first.

## Reporting bugs and proposing features

Open an issue on the project repository before sending a non-trivial
patch. We want to align on scope before you spend time on an
implementation. For security-relevant issues see
[`SECURITY.md`](SECURITY.md) — those should *not* go through the public
issue tracker.

When reporting a bug, include:

- the `ltk` version (commit hash if you built from source),
- the Rust toolchain (`rustc --version`),
- the compositor and OS,
- a minimal reproducer (Rust source preferred over screenshots),
- whether the issue happens on both the GLES and the software backend
  (set `LTK_FORCE_SOFTWARE=1` to force software).

## Building and testing

The project requires the Rust toolchain shipped with Debian stable
(currently 1.85). On Debian / Ubuntu:

```bash
sudo apt-get install \
    libwayland-dev libegl-dev libxkbcommon-dev pkg-config

git clone <repo>
cd ltk
cargo build
cargo test --features test-support
```

Tests require the `test-support` feature: the `test_support` module is
feature-gated in `src/lib.rs`, and the code under `tests/` and
`benches/` imports it, so a bare `cargo test` fails to compile.

The `Makefile` wraps the common targets:

```bash
make all          # cargo build --release
make test         # cargo test --features test-support
make doctest-md   # typecheck the Rust snippets in docs/*.md
make stylecheck   # mechanical style checks (tabs, attribute spacing)
make clippy       # semantic lints, warnings as errors (mirrors CI)
make audit        # cargo audit (installs cargo-audit on first run)
make doc          # cargo doc --no-deps
make examples     # run every example under examples/ in turn
make clean        # runs dh_clean, so it needs debhelper installed
```

Run `make doctest-md` after editing any file under `docs/` — it feeds
each markdown file to `rustdoc --test` to catch API drift in the
snippets.

Running the examples requires a Wayland session and the default theme
on disk:

```bash
export LTK_THEMES_DIR="$PWD/themes"
cargo run --example showcase
```

## Code style

`ltk` uses a custom **Modified Allman** style. `rustfmt`'s default
settings do not match it; do not run `cargo fmt`. The full rules live
in [`code_style_guide.md`](code_style_guide.md), but the headline points
are:

- **tabs** for indentation (never spaces),
- opening `{` on its **own new line** for `fn`, `impl`, `struct`,
  `enum`, `mod`, `if`, `for`, `while`, `match`, `loop`,
- `} else {` and `} else if … {` on the same line as the closing brace
  (compact else),
- spaces inside non-empty parentheses: `fn foo( x: i32 )`,
  `bar( arg )`, `Some( x )`, `Ok( v )`,
- spaces inside non-empty attribute brackets: `#[ derive( Clone, Debug ) ]`,
- no spaces inside `<>` generics: `Vec<String>`, `Option<i32>`,
- comments in **English** — never another language.

Match the surrounding code when in doubt.

## Patch shape

- Keep changes focused: one logical change per pull request. A bug fix
  and a refactor go in separate PRs.
- Add tests. The repository has ~680 tests covering the existing
  surface, and a contribution that adds behaviour without test
  coverage will get review pushback. See [`tests/`](tests/) for
  examples of integration tests via `UiSurface`, and the inline
  `#[cfg(test)] mod tests` blocks under `src/` for unit tests.
- Document new public API. Every `pub` item exported from the crate
  root is expected to have a `///` rustdoc comment with at minimum a
  one-paragraph description and an example. Module-level `//!`
  comments are required for new submodules.
- Don't break the public API surface without coordinating. Until the
  crate hits `1.0`, breaking changes go in minor versions
  (`0.x.0 → 0.(x+1).0`); patch versions (`0.x.y → 0.x.(y+1)`) keep
  source compatibility.
- Give user-visible changes a `CHANGELOG.md` entry under
  `[Unreleased]`.
- Run `cargo test --features test-support` and `make audit` before
  sending. CI will run them
  again, but it is faster for both of us if your local run is clean.

## Architectural decisions worth knowing

A few patterns recur across the codebase:

- **Builder methods consume `self`** (`pub fn padding( mut self, p: impl Into<Length> ) -> Self`).
  Chaining works because every builder returns `Self`. Don't introduce
  setters that take `&mut self`.
- **Layouts and widgets share `Element<Msg>`.** Anything that converts
  to `Element` can be pushed into any layout. The split between
  [`src/layout/`](src/layout/) and [`src/widget/`](src/widget/) is
  documentation, not architecture.
- **The runtime is single-threaded.** Use `RefCell` for caches inside
  `App` state, never `Mutex`. Cross-thread communication goes through
  [`ChannelSender`](src/app.rs).
- **`view()` must be pure.** No I/O, no allocation-heavy work, no
  state mutation. Cache derived data on the app struct (behind
  `RefCell` if needed) and look it up.
- **Theming is process-global.** There is no per-app theme; the active
  document and mode live in a `RwLock<Arc<…>>`. `view()` reads the
  state, never writes it. Mode flips and document swaps go through
  `ltk::set_active_mode` and `ltk::set_active_document`.
- **Per-frame allocations are fine.** Building the `Element` tree on
  every render is the supported model. Don't try to retain widgets
  across frames.

## License

By submitting a patch you agree it is licensed under
[`LGPL-2.1-only`](LICENSE), the same as the rest of the project. Do not
add `Co-Authored-By` lines or other AI attribution to commit messages.

## Code of conduct

Be respectful. Disagreements are welcome; personal attacks are not.
Maintainers will moderate threads that go off the rails.
