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Version: 0.1.0

Introduction

Reactive Documents for Typst

Loom is a meta-engine that brings bidirectional data flow, global state management, and component reactivity to Typst.

It transforms Typst from a linear typesetting system into a multi-pass application runtime, allowing you to build complex, data-driven templates that are impossible in standard Typst.

Why Loom?​

Typst is an incredible layout engine, but its execution model is strictly linear (top-to-bottom). This creates a fundamental limitation for complex logic: A parent component cannot react to data produced by its children.

The "Linear Wall"​

Imagine you are building a Project Dashboard. You want to list tasks and show a progress bar at the top.

  • In Standard Typst: You must calculate the progress before you draw the page. This forces you to separate your data (variables) from your view (content), breaking the nice, declarative structure.
  • In Loom: You simply write your tasks. Each task calculates its own status and "signals" it up to the parent. The parent aggregates these signals and draws the progress bar automatically.

How it Works​

Loom wraps your document in a Weave Loop. It runs your code multiple times to resolve dependencies, effectively adding "Time Travel" to Typst.

  1. Discovery: Loom runs your document to find all components and collect their signals (e.g., "I am Task A, and I am complete").
  2. Reaction: Loom runs again, injecting the collected data back into the top. Now the parent knows the total status before it draws.
  3. Convergence: The loop repeats until the data stabilizes.

Key Features​

  • ⚡ Bidirectional Data Flow:
    • Scope (Down): Pass configuration (Themes, Chapter Numbers) down to deep descendants without parameter drilling.
    • Signals (Up): Components emit data (Prices, Metadata) that bubbles up to be aggregated by parents.
  • 🔄 Convergence Engine: Automatically resolves dependencies (e.g., A needs B, B needs C) by running until stable.
  • 🛡️ Architectural Guards: Enforce structure (e.g., "This Slide must be inside a Presentation") with clear error messages.
  • 📦 Component Model: Build self-contained "Motifs" that manage their own state and logic.

When to use Loom?​

Loom is designed for Structured Documents where components need to talk to each other.

Use Loom for...Do NOT use Loom for...
Dashboards & Reports (Aggregating totals, charts)Simple Essays (Standard Typst is fine)
Complex Templates (RPGs, Invoices, CVs)Particle Simulations (Too much overhead)
Libraries (Providing robust, crash-proof components)One-off scripts

Getting Started​

Ready to change how you think about Typst?