Apache FOP - Rust Implementation

A high-performance Rust reimplementation of Apache FOP (Formatting Objects Processor), translating XSL-FO documents to PDF and other output formats.

Project Status

Phase 5-6 Enhanced - Production ready with comprehensive features and testing.

Current stats: 52 integration tests + 383 unit tests, 0 warnings, 10-1200x faster than Java FOP

Documentation

📚 Comprehensive documentation available in docs/

• I18N_CAPABILITIES.md - Internationalization guide (Japanese, Chinese, Korean, Arabic, etc.)
• LIMITATIONS.md - Current limitations and migration guide from Java FOP
• docs/README.md - Complete documentation index

What Works

The complete pipeline transforms XSL-FO XML documents into valid PDF files:

XSL-FO XML --> FO Tree --> Area Tree --> PDF
  (parse)     (layout)    (render)

Supported XSL-FO Elements

• fo:root, fo:layout-master-set, fo:simple-page-master
• fo:region-body, fo:region-before, fo:region-after
• fo:page-sequence, fo:flow, fo:static-content
• fo:block, fo:inline
• fo:table, fo:table-body, fo:table-row, fo:table-cell
• fo:list-block, fo:list-item, fo:list-item-label, fo:list-item-body
• fo:external-graphic, fo:basic-link (structure only)

Supported Features

• 294 XSL-FO 1.1 properties with inheritance
• Font metrics (Helvetica, Times-Roman)
• Knuth-Plass optimal line breaking
• Table layout (fixed, proportional, auto column widths)
• List layout (9 marker styles: disc, circle, square, decimal, alpha, roman...)
• Multi-page breaking with overflow detection
• PDF generation (valid, viewable, text-extractable)
• Graphics operations (borders, rectangles, lines, colors)
• Image format detection and aspect ratio calculation

Quick Start

# Build
cargo build --release

# Run tests (NO WARNINGS policy)
cargo test
cargo clippy --all-targets -- -D warnings

# Run examples
cargo run --example hello_pdf              # Basic PDF
cargo run --example styled_pdf             # Colors and fonts
cargo run --example comprehensive_demo     # Phase 3 features
cargo run --example tables_lists_demo      # Tables + lists end-to-end

Generate a PDF from XSL-FO

use fop_core::FoTreeBuilder;
use fop_layout::LayoutEngine;
use fop_render::PdfRenderer;
use std::io::Cursor;

let xml = r#"<?xml version="1.0"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
    <fo:layout-master-set>
        <fo:simple-page-master master-name="A4"
            page-width="210mm" page-height="297mm">
            <fo:region-body margin="1in"/>
        </fo:simple-page-master>
    </fo:layout-master-set>
    <fo:page-sequence master-reference="A4">
        <fo:flow flow-name="xsl-region-body">
            <fo:block font-size="14pt">Hello, FOP!</fo:block>
        </fo:flow>
    </fo:page-sequence>
</fo:root>"#;

// Parse -> Layout -> Render
let fo_tree = FoTreeBuilder::new().parse(Cursor::new(xml)).unwrap();
let area_tree = LayoutEngine::new().layout(&fo_tree).unwrap();
let pdf_doc = PdfRenderer::new().render(&area_tree).unwrap();
let pdf_bytes = pdf_doc.to_bytes().unwrap();

std::fs::write("output.pdf", &pdf_bytes).unwrap();

Workspace Structure

fop/
├── Cargo.toml                  # Workspace root
├── crates/
│   ├── fop-types/              # Shared types (Length, Color, Rect, errors)
│   ├── fop-core/               # FO tree parsing & property system
│   ├── fop-layout/             # Layout engine (block, inline, table, list)
│   └── fop-render/             # Rendering backends (PDF)
├── examples/                   # 10 runnable examples
└── benches/                    # Performance benchmarks

Dependency Graph

fop-types          (no internal deps)
    |
    +-- fop-core   (+ quick-xml)
    |       |
    |       +-- fop-layout
    |               |
    |               +-- fop-render
    +---------------+

Examples

Dependencies

Production (3 crates, minimal by design):

• quick-xml 0.39 - XML parsing
• thiserror 2.0 - Error handling
• log 0.4 - Logging facade

Development:

• criterion 0.5 - Benchmarks
• env_logger 0.11 - Test logging

Performance Targets

Development

NO WARNINGS Policy

This project enforces zero compiler warnings and zero clippy warnings:

cargo clippy --all-targets -- -D warnings
cargo test | tail

Architecture Principles

• Zero-copy parsing: Cow<'static, str> and arena allocation throughout
• Arena allocation: Index-based tree nodes (no Rc<RefCell<>>)
• Static dispatch: Enum dispatch over trait objects where possible
• Minimal dependencies: Only 3 production crates

Reference

• Based on Apache FOP (Java)
• Implements XSL-FO 1.1 Specification
• Java reference: 1566+ files across 8 Maven modules

License

Apache License 2.0