# ttx-diff
[](https://pypi.org/project/ttx-diff/)
[](https://pypi.org/project/ttx-diff/)
A tool for comparing font compiler outputs between fontc (Rust) and fontmake (Python).
## Overview
`ttx-diff` is a helper utility that compares binary font outputs from two different font compilers:
- **fontc**: The Rust-based font compiler from Google Fonts
- **fontmake**: The Python-based font compiler
The tool converts each binary font to TTX (XML) format, normalizes expected differences, and provides a detailed comparison summary.
## Installation
### From PyPI
```bash
pip install ttx-diff
```
### From source
```bash
git clone https://github.com/googlefonts/fontc.git
cd fontc/ttx_diff
pip install -e .
```
## Requirements
- Python 3.10 or higher
- `fontc` and `otl-normalizer` binaries (see below)
All Python dependencies (fontmake, fonttools, etc.) are installed automatically.
### Getting fontc and otl-normalizer
The tool needs the `fontc` and `otl-normalizer` binaries. You can:
1. **Specify paths explicitly** (recommended for most users):
```bash
ttx-diff --fontc_path /path/to/fontc --normalizer_path /path/to/otl-normalizer source.glyphs
```
2. **Add them to your PATH**: If `fontc` and `otl-normalizer` are in your PATH, they'll be found automatically
3. **Run from fontc repository**: If you run from the fontc repository root, the tool will automatically build the binaries for you
## Usage
**Note**: Unlike the original `ttx_diff.py` script, this standalone version can be run from any directory. You don't need to be in the fontc repository.
Rebuild with both fontmake and fontc and compare:
```bash
ttx-diff --fontc_path /path/to/fontc --normalizer_path /path/to/otl-normalizer path/to/source.glyphs
```
If the binaries are in your PATH:
```bash
ttx-diff path/to/source.glyphs
```
Rebuild only fontc's font and reuse existing fontmake output:
```bash
ttx-diff --rebuild fontc path/to/source.glyphs
```
Output results in machine-readable JSON format, as used by the [`fontc_crater`](https://github.com/googlefonts/fontc/tree/main/fontc_crater) tool.
```bash
ttx-diff --json path/to/source.glyphs
```
Compare using gftools build pipeline:
```bash
ttx-diff --compare gftools --config config.yaml path/to/source.glyphs
```
## Development
Running tests
```bash
pip install -e .[test]
pytest
```
Running tests with coverage
```bash
pytest --cov=ttx_diff --cov-report=html
```
## Releasing
See <https://googlefonts.github.io/python#make-a-release>.
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"description": "# ttx-diff\n\n[](https://pypi.org/project/ttx-diff/)\n[](https://pypi.org/project/ttx-diff/)\n\nA tool for comparing font compiler outputs between fontc (Rust) and fontmake (Python).\n\n## Overview\n\n`ttx-diff` is a helper utility that compares binary font outputs from two different font compilers:\n- **fontc**: The Rust-based font compiler from Google Fonts\n- **fontmake**: The Python-based font compiler\n\nThe tool converts each binary font to TTX (XML) format, normalizes expected differences, and provides a detailed comparison summary.\n\n## Installation\n\n### From PyPI\n\n```bash\npip install ttx-diff\n```\n\n### From source\n\n```bash\ngit clone https://github.com/googlefonts/fontc.git\ncd fontc/ttx_diff\npip install -e .\n```\n\n## Requirements\n\n- Python 3.10 or higher\n- `fontc` and `otl-normalizer` binaries (see below)\n\nAll Python dependencies (fontmake, fonttools, etc.) are installed automatically.\n\n### Getting fontc and otl-normalizer\n\nThe tool needs the `fontc` and `otl-normalizer` binaries. You can:\n\n1. **Specify paths explicitly** (recommended for most users):\n ```bash\n ttx-diff --fontc_path /path/to/fontc --normalizer_path /path/to/otl-normalizer source.glyphs\n ```\n\n2. **Add them to your PATH**: If `fontc` and `otl-normalizer` are in your PATH, they'll be found automatically\n\n3. **Run from fontc repository**: If you run from the fontc repository root, the tool will automatically build the binaries for you\n\n## Usage\n\n**Note**: Unlike the original `ttx_diff.py` script, this standalone version can be run from any directory. You don't need to be in the fontc repository.\n\nRebuild with both fontmake and fontc and compare:\n\n```bash\nttx-diff --fontc_path /path/to/fontc --normalizer_path /path/to/otl-normalizer path/to/source.glyphs\n```\n\nIf the binaries are in your PATH:\n\n```bash\nttx-diff path/to/source.glyphs\n```\n\nRebuild only fontc's font and reuse existing fontmake output:\n\n```bash\nttx-diff --rebuild fontc path/to/source.glyphs\n```\n\nOutput results in machine-readable JSON format, as used by the [`fontc_crater`](https://github.com/googlefonts/fontc/tree/main/fontc_crater) tool.\n\n```bash\nttx-diff --json path/to/source.glyphs\n```\n\nCompare using gftools build pipeline:\n\n```bash\nttx-diff --compare gftools --config config.yaml path/to/source.glyphs\n```\n\n## Development\n\nRunning tests\n\n```bash\npip install -e .[test]\npytest\n```\n\nRunning tests with coverage\n\n```bash\npytest --cov=ttx_diff --cov-report=html\n```\n\n## Releasing\n\nSee <https://googlefonts.github.io/python#make-a-release>.\n",
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