pdf/docs/phase0.md

# Phase 0 — Infrastructure

> Goal of Phase 0: **make the entire stack compile and run on Linux, macOS, and
> Windows.** No editing, no rendering features. Success = the engine library
> builds clean on all three platforms and the smoke test passes. Phase 1 does
> not begin until Gate G0 and G0b are reached.

## Phase 0 task board

| # | Task | Owner | This session |
|---|------|-------|--------------|
| 1 | CMake root + vcpkg + CI/CD pipeline       | Dev 1 | **Done — scaffolded** |
| 2 | PDFium build (depot_tools + GN + Ninja)   | Dev 1 | Build scripts staged; not yet run |
| 3 | Skia build integration                    | Dev 2 | Not started |
| 4 | FreeType + HarfBuzz vcpkg integration      | Dev 3 | In manifest; wrappers not started |
| 5 | FastAPI service scaffolding                | Dev 1 | Placeholder dir only |
| 6 | React + TypeScript frontend scaffolding    | Dev 2 | Placeholder dir only |
| 7 | WASM hello-world build (Emscripten)        | Dev 1 | Toolchain hook + preset stubbed |
| 8 | Frozen interface contracts (Gate G0b)      | All   | Placeholder header; **not designed** |

This session delivered **Task 1 in full** plus the repository structure for
everything else. Scope was deliberately limited to the build pipeline — see
"What is intentionally not done" below.

## What was built this session

```
Code/
├── CMakeLists.txt              root build; refuses to configure without a pinned baseline
├── CMakePresets.json           debug/release/asan per platform + a wasm stub
├── vcpkg.json                  dependency manifest (freetype, harfbuzz, spdlog, gtest)
├── .clang-format .clang-tidy    style + naming rules from blueprint §16.1
├── .gitignore .gitattributes .editorconfig
├── cmake/
│   ├── pdfium.cmake            turns the PDFium install tree into pdfium::pdfium
│   ├── CompilerWarnings.cmake  high warning levels per compiler
│   ├── Sanitizers.cmake        ASan/UBSan wiring
│   └── toolchains/wasm.cmake   Emscripten hook (stub)
├── engine/
│   ├── CMakeLists.txt
│   ├── include/pdfengine/      public headers (version, umbrella, pdf_document placeholder)
│   ├── src/core/               engine_info.cpp — version/build introspection
│   ├── src/parser/             pdfium_loader — the ONLY FPDF_-allowed dir (Rule R2)
│   └── tests/                  gtest smoke test backing Gate G0
├── third_party/pdfium/         from-source build scripts + pinned-ref file + args.gn
├── scripts/
│   ├── bootstrap.{sh,ps1}      installs vcpkg, pins the dependency baseline
│   └── check_pdfium_boundary.{sh,ps1}   Rule R2 enforcement
├── .github/workflows/ci.yml    Linux/macOS/Windows build matrix + lint jobs
├── bindings/ gateway/ frontend/ wasm/ corpus/   placeholder dirs with READMEs
└── docs/phase0.md              this file
```

## How to build (developer onboarding)

### Prerequisites

| Tool | Version | Notes |
|------|---------|-------|
| CMake | >= 3.25 | presets v6 |
| Ninja | any recent | the only generator used |
| C++ compiler | MSVC 19.36+ / GCC 13+ / Clang 16+ | needs C++23 |
| vcpkg | — | `scripts/bootstrap` installs it if `VCPKG_ROOT` is unset |
| Git | any recent | |
| clang-format | 22.1.5 | not natively packaged on Windows — `pip install clang-format==22.1.5` (CI is pinned to this exact version) |

> **Windows:** either Visual Studio 2022/2026 (with the *"Desktop development
> with C++"* workload) or **Build Tools 2026** (no IDE — installer product
> `Microsoft.VisualStudio.Product.BuildTools`) is supported. `cl.exe` is not on
> `PATH` by default — run builds from a *Developer PowerShell* or import
> `VC\Auxiliary\Build\vcvars64.bat` first. Build Tools is not a default
> `vswhere` product, so detection scripts need `vswhere -products *` (the
> PDFium build script already does this). CI uses `ilammy/msvc-dev-cmd`.
>
> `VCPKG_ROOT` set via `setx` (or the bootstrap script's persistent install)
> does **not** propagate into already-open shells — set `$env:VCPKG_ROOT`
> explicitly in that shell, or open a new terminal. PowerShell 5.1 is fine;
> `pwsh` (7+) is not required by anything in this repo.

### Steps

```sh
# 1. One-time setup — checks tools, installs vcpkg, pins the dependency baseline.
pwsh scripts/bootstrap.ps1        # Windows
./scripts/bootstrap.sh            # Linux / macOS

# 2. Configure + build + test.
cmake --preset windows-debug      # linux-debug | macos-debug
cmake --build --preset windows-debug
ctest --preset windows-debug
```

The first configure compiles the vcpkg dependencies (freetype, harfbuzz,
spdlog, gtest) — slow once, cached after.

### Building with PDFium

PDFium is built separately from source (Task 2):

```sh
# Pin the revision first — edit third_party/pdfium/pdfium.pinned (see its README).
pwsh third_party/pdfium/build_pdfium.ps1     # or .sh
```

Until then the engine builds with PDFium code paths `#ifdef`-ed out, which is
the correct Phase 0 default — it keeps the pipeline green while Task 2 runs.

On Linux/macOS, enabling PDFium is a single flag added to a debug build:

```sh
cmake --preset linux-debug -DPDFENGINE_WITH_PDFIUM=ON
```

On Windows there is more to it — see the next section.

### Windows + PDFium

PDFium's static-lib GN build forces the static CRT (`/MT`, `is_debug=false`)
and offers no knob for "static lib + dynamic CRT". The engine, vcpkg deps,
and PDFium must therefore all use the same static CRT, or the link dies with
`LNK2038: 'RuntimeLibrary' mismatch`. The repo is wired for this ("Option A,
all static CRT, release-flavored"):

- The hidden `windows-base` preset in [CMakePresets.json](../CMakePresets.json)
  sets `VCPKG_TARGET_TRIPLET=x64-windows-static` (vcpkg deps as static lib +
  static CRT — first configure rebuilds them, ~7 min one-time) and
  `CMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded$<$<CONFIG:Debug>:Debug>`.
- PDFium's own [args.gn](../third_party/pdfium/args.gn) keeps `is_debug=false`
  (i.e. `/MT`).
- The PDFium-linked engine build must be **RelWithDebInfo, not Debug** — a
  Debug engine is `/MTd` and still mismatches PDFium's `/MT`. The plain
  `windows-debug -DPDFENGINE_WITH_PDFIUM=ON` recipe will not link; use the
  `win-local-pdfium` user preset below.

#### `win-local-pdfium` user preset

`CMakeUserPresets.json` is git-ignored (build dirs are per-developer and live
outside OneDrive). Drop this preset in at `Code/CMakeUserPresets.json`, with
your own username in `binaryDir`:

```json
{
  "version": 6,
  "configurePresets": [
    {
      "name": "win-local-pdfium",
      "inherits": "windows-release",
      "binaryDir": "C:/Users/<you>/pdfeng-build/win-local-pdfium",
      "cacheVariables": { "PDFENGINE_WITH_PDFIUM": "ON" }
    }
  ],
  "buildPresets": [
    { "name": "win-local-pdfium", "configurePreset": "win-local-pdfium" }
  ],
  "testPresets": [
    { "name": "win-local-pdfium", "inherits": "common", "configurePreset": "win-local-pdfium" }
  ]
}
```

Then, from a shell with `vcvars64.bat` imported:

```powershell
cmake --preset win-local-pdfium
cmake --build --preset win-local-pdfium
ctest --preset win-local-pdfium
```

Success looks like `pdfengine_smoke.exe` linking cleanly and logging
`pdfium=on`. The build dir is intentionally outside OneDrive and on a
space-free path — see the OneDrive section below for why.

#### Gotcha: depot_tools shadows `ninja`

The PDFium build adds `depot_tools` to `PATH` and the depot_tools `ninja` /
`ninja.bat` are not real Ninja — they fail with:

```
Running ninja --version failed with unknown error
... CMAKE_CXX_COMPILER not set, after EnableLanguage
```

If `depot_tools` ended up on your persistent `PATH`, CMake will pick its
broken `ninja` for the engine build. Two fixes:

- **Short-term:** point CMake at the real Ninja explicitly, e.g.
  `cmake --preset win-local-pdfium -D CMAKE_MAKE_PROGRAM=C:/path/to/real/ninja.exe`.
  This caches, so only the first configure needs the flag.
- **Long-term (recommended):** keep `depot_tools` **off** the persistent
  `PATH`. `third_party/pdfium/build_pdfium.ps1` already prepends it
  per-run, so the PDFium build still works.

## Dependency pinning

The blueprint rule is *"pin all dependency versions on Day 1, never track
rolling HEAD."* Two mechanisms:

- **vcpkg deps** — `scripts/bootstrap` runs `vcpkg x-update-baseline
  --add-initial-baseline`, which writes a `builtin-baseline` commit into
  `vcpkg.json`. That pins the entire dependency registry to one commit. The
  root `CMakeLists.txt` **refuses to configure** until this is present.
  → **The first commit to the repo must include the bootstrapped `vcpkg.json`**,
  otherwise CI fails at the configure step (by design).
- **PDFium** — `third_party/pdfium/pdfium.pinned` holds an exact commit SHA.
  The build script refuses to run while it is the placeholder. Rebases are a
  deliberate, scheduled (quarterly) action.

## Engineering conventions

- **Naming** (`.clang-tidy`): `CamelCase` types, `camelBack` functions,
  `snake_case` file names.
- **Errors**: `std::expected<T, E>` internally; `int error_code` across the C ABI.
- **Branches**: `main`, `develop`, `feature/*`, `release/*`.
- **Rule R2**: only `engine/src/parser/` may use raw `FPDF_*` APIs —
  enforced by `scripts/check_pdfium_boundary.*` locally and in CI.

## What is intentionally NOT done this session

- **PDFium is not actually built** — scripts are staged; the revision needs to
  be pinned and the (long) build run as the second half of Task 2.
- **No interface contracts** — `engine/include/pdfengine/pdf_document.hpp` is a
  placeholder. `PdfDocument` / `PdfPage` are designed and frozen at **Gate G0b**
  in an all-devs session; nothing proceeds until it is signed off.
- **Skia / FreeType / HarfBuzz wrappers** — FreeType + HarfBuzz are in the vcpkg
  manifest and link-tested, but the actual wrappers are Dev 3's Phase 0/1 work.
  Skia is Dev 2's task.
- **FastAPI / React / WASM** — placeholder directories only. WASM has a toolchain
  hook and preset stub so the integration point exists (Rule R5: WASM never
  blocks shipping).

## Gates ahead

| Gate | Criterion | Unblocks |
|------|-----------|----------|
| **G0**  | All platforms build clean; PDFium + Skia + FreeType + HarfBuzz compile | Phase 1 |
| **G0b** | `PdfDocument` / `PdfPage` contracts locked by all 3 devs | Coding begins |

The CI `build` matrix is the automated half of G0. The smoke test
(`engine/tests/smoke_test.cpp`) is what it runs.

## OneDrive warning

This checkout lives under `OneDrive\Work\Maskan\PDF Editor\Code`. The path is
both OneDrive-synced **and** contains a space (`PDF Editor`). Both bite C++
builds:

1. **Sync churn** — build output is thousands of `.obj`/`.o` files. `out/` is
   git-ignored, but OneDrive still tries to upload it.
2. **File locks** — OneDrive can hold a handle on a file mid-sync, causing
   intermittent "permission denied" errors during compile or link.
3. **Spaces in build paths break tooling** — vcpkg/meson (harfbuzz) fail
   with `LNK1181` when `vcpkg_installed` is under the spaced path, and
   `depot_tools` / GN / Ninja `.bat` wrappers cannot handle a space in their
   own path at all.

**On Windows, building inside the repo path is not viable** — put the build
dir outside OneDrive on a space-free path. The `win-local-pdfium` preset
above already does this (`C:/Users/<you>/pdfeng-build/...`); do the same for
any non-PDFium preset by overriding `binaryDir`:

```powershell
cmake --preset windows-release -B C:/Users/<you>/pdfeng-build/windows-release
```

The PDFium build is even stricter: `third_party/pdfium/build_pdfium.ps1`
takes a `PDFIUM_BUILD_ROOT` env var and hard-errors if it contains a space.
Use e.g. `C:\Users\<you>\pdfium-build`.

On Linux/macOS the OneDrive path is still a sync nuisance but the toolchain
itself is fine. Either point the build dir outside OneDrive, or exclude
`out/` and `vcpkg/` from sync, or pause sync while building.

Long term, the repository should live outside OneDrive on a real Git remote.