ConformalLabpp/doc/getting-started.md

# Getting Started

## Prerequisites

| Tool | Minimum | Notes |
|---|---|---|
| C++ compiler (GCC or Clang) | C++17 | GCC 11+ or Clang 14+ recommended |
| CMake | 3.20 | |
| Boost headers | 1.70 | Only for `-DWITH_CGAL_TESTS=ON` or `-DWITH_CGAL=ON` |
| Wayland/X11 dev headers | — | Only for `-DWITH_CGAL=ON` (viewer) |

All other dependencies (Eigen 3.4, CGAL 6.1.1, libigl 2.6, GLFW 3.4, GTest 1.14)
are bundled as tarballs in `code/deps/tarballs/` and extracted automatically at CMake
configure time. No internet access is required at build time (except GTest, fetched via
`FetchContent` from GitHub).

Install Boost on your system:
```bash
# Ubuntu / Debian
apt install libboost-dev

# macOS
brew install boost
```

---

## Clone

```bash
git clone https://codeberg.org/TMoussa/ConformalLabpp
cd ConformalLabpp
```

---

## Build modes

Three modes with increasing dependencies:

### Mode 1 — Fast tests (default, no system dependencies)

Pure-math tests: Clausen functions, hyper-ideal geometry, matrix utilities.

```bash
cmake -S code -B build
cmake --build build --target conformallab_tests -j$(nproc)
ctest --test-dir build --output-on-failure
```

Expected: **36 tests pass**.

### Mode 2 — CGAL tests, headless (recommended for CI and development)

Full CGAL test suite. Requires Boost headers only — no display, no Wayland, no GLFW.

```bash
cmake -S code -B build -DWITH_CGAL_TESTS=ON
cmake --build build --target conformallab_cgal_tests -j$(nproc)
ctest --test-dir build -R "^cgal\." --output-on-failure
```

Expected: **173 tests pass, 1 skipped** (intentional stub for analytic HyperIdeal Hessian, Phase 9b).

### Mode 3 — Full local build (CLI app + interactive viewer)

Requires Wayland or X11 development packages (`wayland-scanner`, `libx11-dev`, etc.).
Automatically enables the viewer library (GLFW + libigl).

```bash
cmake -S code -B build -DWITH_CGAL=ON
cmake --build build -j$(nproc)
```

> **Note:** `-DWITH_CGAL=ON` implies `-DWITH_VIEWER=ON`. Do not use this in headless
> environments — it will fail with `Failed to find wayland-scanner`.

---

## Running a single test

```bash
# By GTest filter (fastest, full output)
./build/conformallab_cgal_tests --gtest_filter="NewtonSolver*"
./build/conformallab_tests       --gtest_filter="Clausen*"

# By CTest regex
ctest --test-dir build -R "cgal.NewtonSolver" --output-on-failure
```

All CGAL tests have the prefix `cgal.` in CTest (set in `tests/cgal/CMakeLists.txt`
via `TEST_PREFIX "cgal."`).

---

## First run — CLI app

After a full build (`-DWITH_CGAL=ON`):

```bash
# Euclidean conformal layout
./bin/conformallab_core -i input.off -g euclidean -o layout.off -j result.json

# Spherical layout
./bin/conformallab_core -i input.off -g spherical -o sphere.off

# Hyperbolic layout (HyperIdeal)
./bin/conformallab_core -i input.off -g hyper_ideal -o hyperbolic.off

# Show input mesh in interactive viewer
./bin/conformallab_core -i input.off -s

# All options
./bin/conformallab_core --help
```

## Example programs

```bash
./build/examples/example_layout    [input.off] [layout.off] [result.json]
./build/examples/example_euclidean [input.off] [output.off]
./build/examples/example_hyper_ideal [input.off] [output.off]
./build/examples/example_viewer    [input.off]   # interactive, requires WITH_VIEWER
```

`example_layout.cpp` is the best starting point — it shows the complete pipeline in ~120 lines.

**Expected output of `example_euclidean` on the built-in quad-strip mesh:**
```
[example_euclidean] No input file given — using make_quad_strip().
[example_euclidean] Mesh: 6 vertices, 4 faces.
[example_euclidean] DOFs: 5 (1 vertex pinned).
[example_euclidean] Solving Newton system…
[example_euclidean] Converged in 1 iterations.  ||G||_inf = 0
[example_euclidean] Per-vertex conformal factors u_i:
  v0  u = 0  (pinned)
  v1  u = -1.38778e-17       ← ≈ 0 (machine epsilon)
  ...
[example_euclidean] Mesh saved to: /tmp/conformallab_euclidean_out.off
```
Convergence in 1 iteration is expected: the "natural equilibrium" construction
sets x* = 0, so a small perturbation (-0.05) needs only one Newton step.

**Quick automated start (no interactive build needed):**
```bash
bash scripts/try_it.sh
```
This clones nothing (run from inside the repo), builds the CGAL test suite, runs
all 173+36 tests, and prints a summary.  See `scripts/try_it.sh` for details.

---

## Known issues

### macOS Finder duplicates

macOS Finder sometimes creates duplicate files named `foo 2.hpp` when copying
the repository.  These cause confusing compile errors ("redefinition of …").

**Fix (run once from the repo root):**
```bash
find code/include -name "* 2.*" -delete
find code/include -name "*\ 2.*" -delete
```

Files without a ` 2` suffix are always canonical — the duplicates are safe to delete.

### First build is slow

The first CMake configure extracts four tarballs (Eigen 3.4, CGAL 6.1.1,
libigl 2.6, GLFW 3.4) and downloads GTest via `FetchContent`.
Allow **30–90 seconds** for the first configure.  Subsequent builds are fast
(< 10 s incremental).

---

## Rebuilding the CI Docker image

The CI runner is a self-hosted Raspberry Pi (ARM64). After changes to
`.gitea/docker/Dockerfile.ci-cpp`:

```bash
docker buildx build \
  --platform linux/arm64 \
  -f .gitea/docker/Dockerfile.ci-cpp \
  -t git.eulernest.eu/conformallab/ci-cpp:latest \
  --push \
  .gitea/docker/
```