# tc-lib-pdf-font

> Font import, metrics, and stack management utilities for PDF generation.

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---

## Overview

`tc-lib-pdf-font` provides font import and runtime font-stack services used by PDF composition engines.

It bridges static font assets and runtime document composition by handling metrics, encodings, and font program references in a PDF-friendly way. This modular design lets applications evolve font workflows independently from the rest of the rendering stack.

| | |
|---|---|
| **Namespace** | `\Com\Tecnick\Pdf\Font` |
| **Author** | Nicola Asuni <info@tecnick.com> |
| **License** | [GNU LGPL v3](https://www.gnu.org/copyleft/lesser.html) - see [LICENSE](LICENSE) |
| **API docs** | <https://tcpdf.org/docs/srcdoc/tc-lib-pdf-font> |
| **Packagist** | <https://packagist.org/packages/tecnickcom/tc-lib-pdf-font> |

---

## Features

### Font Processing
- Import support for core, Type1, and TrueType sources
- Font metadata extraction and normalization
- Utilities for subset and output dictionary generation
- Optional injectable cache to reuse computed TrueType font subsets

### Runtime Font Stack
- Font stack insertion and switching
- Glyph width/bounding-box helpers
- Character replacement and fallback handling
- Glyph index encoding of composite fonts, with support for the supplementary planes

---

## Requirements

- PHP 8.2 or later
- Extensions: `json`, `zlib`
- Composer

---

## Installation

```bash
composer require tecnickcom/tc-lib-pdf-font
```

---

## Quick Start

```php
<?php

require_once __DIR__ . '/vendor/autoload.php';

$font = new \Com\Tecnick\Pdf\Font\Import('/path/to/font.ttf');
$metrics = $font->getFontMetrics();

var_dump($font->getFontName(), $metrics['type']);
```

For larger examples, refer to `test/OutputTest.php` and the conversion tooling in this repository.

---

## Character Encoding of Composite Fonts

A `TrueTypeUnicode` font is emitted as a composite (Type0) font with the `Identity-H` encoding, so every character code in a content stream is 2 bytes wide.

Since version 4.0 the character code is the glyph index of the font (`CID == GID`): the font dictionary declares `/CIDToGIDMap /Identity`, the `/W` array is keyed by glyph index, and a `/ToUnicode` CMap is generated for the glyphs used by the document so that the text stays searchable and extractable. Earlier versions used the Unicode codepoint as the character code and embedded a 131072-byte `CIDToGIDMap` stream, which limited the addressable characters to the Basic Multilingual Plane.

### Encoding a string

The consumer of this library must encode composite text through the font stack, so that the glyphs used are recorded for the `/W` array and the `/ToUnicode` CMap:

```php
$stack = new \Com\Tecnick\Pdf\Font\Stack(1.0);
$stack->insert($objnum, 'dejavusans', '', 12);

if ($stack->isCurrentGidEncoded()) {
    // 2-byte big-endian glyph indices, and the glyphs are recorded on the font
    $codes = $stack->ordArrToGidStr([0x41, 0x20, 0x1D703]);
} else {
    // CID-0 fonts keep the UTF-16BE encoding expected by their predefined CMap
    $codes = $uniconv->toUTF16BE($str);
}
```

The text object written to the page must also select the font the string was encoded with, otherwise the glyph indices are resolved against a different font. This does not apply to the fonts that are not GID encoded, whose character codes mean the same thing in every font.

Relevant methods:

- `Stack::isCurrentGidEncoded()`: true when the current font encodes text as glyph indices.
- `Stack::ordArrToGidStr(array $uniarr)`: encodes codepoints as 2-byte glyph indices and records them.
- `Stack::getGidForOrd(int $ord)`: glyph index of a codepoint, `0` when the font has no glyph for it.
- `Buffer::addUsedGid(string $key, int $gid, int $ord)`: records a glyph and the codepoint it was encoded from.

### Font definition files

The glyph index of a codepoint is read at runtime from the `.ctg.z` artifact of the font, so definition files generated by earlier versions keep working for the whole Basic Multilingual Plane without being regenerated. The file must remain next to the `.json` definition file.

Codepoints above U+FFFF do not fit that table and are stored in the definition file under the `ctgu` key:

```json
"ctgu": {"120579": 1588, "119886": 941}
```

That key is only written when the font is converted with `--encoding_id=10`, which selects the format 12 cmap subtable. A definition file carrying `ctgu` is still readable by older versions of the library, which ignore it.

---

## Subset Caching

TrueType font subsetting is computational and memory intensive. When the same
fonts and character sets are embedded repeatedly (for example across many
generated documents), you can inject an optional cache into
`\Com\Tecnick\Pdf\Font\Output` to reuse previously computed subset programs.

Provide any object implementing
`\Com\Tecnick\Pdf\Font\FontSubsetCacheInterface`:

```php
interface FontSubsetCacheInterface
{
    public function get(string $key): ?string;          // null on cache miss
    public function set(string $key, string $subsetFont): void;
}
```

Pass it as the last constructor argument:

```php
$output = new \Com\Tecnick\Pdf\Font\Output(
    $fonts,
    $objectNumber,
    $encrypt,
    $fileHelper,   // or null
    $subsetCache,  // your FontSubsetCacheInterface implementation
);
```

When no cache is supplied (the default), behavior is unchanged and every
subset is recomputed. The library never evicts entries — the injected backend
owns expiration and size limits. The cache key already accounts for the font
program bytes, the cmap-selection metrics, and the requested subset
characters, so distinct inputs never collide.

### Using a PSR-16 cache

No PSR-16 adapter is bundled, because the interface above is intentionally
trivial to wrap around any backend (PSR-16/PSR-6, Symfony Cache, Laravel,
Redis, APCu, …). A correct PSR-16 wrapper is a few lines:

```php
use Com\Tecnick\Pdf\Font\FontSubsetCacheInterface;
use Psr\SimpleCache\CacheInterface;

final class Psr16SubsetCache implements FontSubsetCacheInterface
{
    public function __construct(private CacheInterface $cache) {}

    public function get(string $key): ?string
    {
        $value = $this->cache->get($this->normalize($key));

        return \is_string($value) ? $value : null;
    }

    public function set(string $key, string $subsetFont): void
    {
        $this->cache->set($this->normalize($key), $subsetFont);
    }

    /**
     * PSR-16 only guarantees keys matching [A-Za-z0-9_.] up to 64 chars and
     * reserves {}()/\@: — the library's raw key uses ':' and '-' and is longer,
     * so hash it into a guaranteed-legal, fixed-length key.
     */
    private function normalize(string $key): string
    {
        return 'tclpf_' . \sha1($key);
    }
}
```

The `normalize()` step matters: the library's raw key is human-readable and
works with permissive backends, but stricter PSR-16 implementations may reject
or mangle it. Hashing it keeps the wrapper portable. Note that hashing discards
the readable namespace, so scope the underlying PSR-16 pool to this library if
you share it with other consumers.

---

## Converting Existing Fonts

Use the CLI utilities in `util/` to convert existing font files into the JSON/Z format consumed by this library.

### Convert One or More Fonts

Run `util/convert.php` and pass one or more input files with `--fonts`:

```bash
php util/convert.php \
	--outpath=./target/fonts/custom/ \
	--type=TrueTypeUnicode \
	--flags=32 \
	--encoding_id=10 \
	--fonts=/path/to/MyFont-Regular.ttf,/path/to/MyFont-Bold.ttf
```

The command writes generated font definition files to `--outpath`.

Common options:

- `--type`: Explicit font type (`TrueTypeUnicode`, `TrueType`, `Type1`, `CID0JP`, `CID0KR`, `CID0CS`, `CID0CT`). Leave empty for autodetect.
- `--encoding`: Encoding table (for example `cp1252` for many non-Unicode Type1/Core cases). Omit for Unicode and symbolic fonts.
- `--flags`: PDF descriptor flags. Default is `32` (non-symbolic).
- `--platform_id` and `--encoding_id`: CMAP selection for TrueType Unicode imports (defaults: `3` and `1`). Use `--encoding_id=10` to read the format 12 subtable, which is required for the characters above U+FFFF. It is a safe default: a font without that subtable falls back to the BMP one.
- `--linked`: Link to system font file instead of embedding/copying it (not transportable).

To see full usage help:

```bash
php util/convert.php --help
```

### Bulk Conversion

For batch generation from the mirrored font set:

```bash
cd util
make build
```

This installs `util` dependencies and runs `bulk_convert.php`, which scans the mirror package and writes converted fonts under `target/fonts/`.

Notes:

- `bulk_convert.php` also attempts OTF conversion via FontForge (`fontforge -script otf2ttf.ff ...`) before import.
- If you run bulk conversion directly, customize destination with `php util/bulk_convert.php --outpath=/your/path/`.

---

## Upgrading from 3.x to 4.0

Version 4.0 changes the character codes emitted for `TrueTypeUnicode` fonts from Unicode codepoints to glyph indices, as described in [Character Encoding of Composite Fonts](#character-encoding-of-composite-fonts).

A consumer of this library must be updated together with it:

- Encode composite text with `Stack::ordArrToGidStr()` instead of writing UTF-16BE codepoints, and make the text object select the font the string was encoded with. A consumer that keeps writing codepoints produces PDFs whose text renders as unrelated glyphs, with no error raised.
- A `TrueTypeUnicode` font emits one PDF object less, since the `CIDToGIDMap` stream is not embedded any more. Baselines that compare PDF output byte by byte, or that assert on object numbers, must be regenerated.
- The `TFontData` shape gained the `ctgu`, `gidenc` and `usedgid` keys. Code that builds that array must add them.

Unchanged:

- No method was removed or changed signature. The new members are additions.
- Font definition files and `.ctg.z` artifacts generated by 3.x keep working for the whole Basic Multilingual Plane. Regenerate a font only to gain the characters above U+FFFF, with `--encoding_id=10`.
- The output of `Core`, `TrueType`, `Type1` and `cidfont0` fonts is unchanged.

---

## Development

```bash
make deps
make help
make qa
```

Font generation helpers are also available through Make targets such as `fonts`.

---

## Packaging

```bash
make rpm
make deb
```

For system packages, bootstrap with:

```php
require_once '/usr/share/php/Com/Tecnick/Pdf/Font/autoload.php';
```

---

## Contributing

Contributions are welcome. Please review [CONTRIBUTING.md](CONTRIBUTING.md), [CODE_OF_CONDUCT.md](CODE_OF_CONDUCT.md), and [SECURITY.md](SECURITY.md).

