Layout Engine

The layout engine (s1-layout) paginates documents for PDF export and editor display.

Features

• Knuth-Plass line breaking algorithm
• Widow/orphan control
• Text shaping via rustybuzz (pure Rust HarfBuzz)
• Font loading via fontdb with substitution table
• Hyphenation (English) via Knuth-Liang patterns
• BiDi text support via unicode-bidi
• Table layout with column width distribution
• Image placement with dimension constraints
• Margin collapsing (CSS spec-compliant)

Configuration

#![allow(unused)]
fn main() {
LayoutConfig {
    page_width: 612.0,   // US Letter (points)
    page_height: 792.0,
    margin_top: 72.0,    // 1 inch
    margin_bottom: 72.0,
    margin_left: 72.0,
    margin_right: 72.0,
    min_orphan_lines: 2,
    min_widow_lines: 2,
}
}

Performance

• Full layout of a 10-page document: ~50ms
• Incremental layout: planned (dirty_from_page field exists)
• Font cache: LRU with 50K entry fallback cache