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Elyas Rahimi edited this page Jan 21, 2026 · 4 revisions

Grob Browser - Documentation Hub

Welcome to the Grob Browser documentation. This is your central hub for understanding the architecture, components, and operation of the Grob web browser engine.

Quick Overview

Grob is a modular, high-performance web browser engine written in Rust. It's designed from the ground up to be fast, safe, and easy to understand. The architecture separates concerns into specialized modules that work together to transform HTML and CSS into rendered web pages.

Current Status: Active Development (Alpha)

Key Features:

  • Written in Rust for memory safety and performance
  • Modular architecture with clear separation of concerns
  • Cross-platform support (Windows, macOS, Linux planned)
  • Standards-compliant HTML/CSS processing
  • Extensible design for future enhancements

Documentation Index

Core Rendering Pipeline

The heart of the browser - how content transforms into pixels:

  1. Parser - HTML and CSS parsing

    • Converts text into structured data
    • Handles malformed input gracefully
    • Generates DOM and Stylesheet objects

  2. DOM - Document Object Model

    • In-memory representation of page structure
    • Element hierarchy and tree navigation
    • Foundation for styling and layout

  3. Style - CSS Processing

    • CSS cascade and specificity rules
    • Style matching and inheritance
    • Computed values for layout

  4. Layout - Box Model & Positioning

    • CSS box model implementation
    • Element dimension and position calculation
    • Support for block, inline, and flex layouts

  5. Paint - Rendering Engine

    • Converts layout to visual output
    • Drawing elements, text, and decorations
    • Stacking context and z-index handling

Support Systems

Specialized modules that enable core functionality:

  1. Font - Typography System

    • Font loading and caching
    • Font metrics and glyph rendering
    • System and web font support

  2. Network - HTTP & Resources

    • HTTP request/response handling
    • Resource fetching and caching
    • URL loading and redirect support

  3. JavaScript - Scripting Engine

    • JavaScript execution integration
    • DOM API exposure to scripts
    • Event handling and callbacks

  4. Platform - OS Abstraction

    • Cross-platform compatibility layer
    • File system and system information access
    • Platform-specific implementations

Application & Architecture

  1. Browser - Application Layer

    • Window management and user interface
    • Event loop and rendering coordination
    • User interaction handling

  2. Architecture - System Design

    • High-level component relationships
    • Data flow and processing pipeline
    • Module dependencies and interfaces

Getting Started

Understanding the System

New to Grob? Start here:

  1. Read this index overview
  2. Review Architecture for the big picture
  3. Pick a component that interests you based on your needs

Want to know...

  • How HTML becomes a page? → See the Core Pipeline section above
  • How styles are applied? → Read Style
  • How text is rendered? → Check Font
  • How pages load? → Look at Network

Building & Running

# Build the project
cargo build

# Run in debug mode
cargo build --debug
cargo run -p grob_browser

# Run in release mode (optimized)
cargo build --release
cargo run --release -p grob_browser

See the main README.md for detailed build instructions.

Architecture at a Glance

Rendering Pipeline

HTML Input
    ↓
[Network] → Fetch resources
    ↓
[Parser] → Build DOM & Stylesheets
    ↓
[Style] → Apply CSS rules
    ↓
[Layout] → Calculate positions/sizes
    ↓
[Paint] → Generate rendering instructions
    ↓
[Browser] → Display in window

Component Dependencies

Browser (Application)
  ↓
Engine (Core)
  ├─ Parser ─────────────────┐
  ├─ DOM                     │
  ├─ Style ─────────────────┐│
  ├─ Layout ────────────────┐││
  ├─ Paint ─────────────────┐│││
  ├─ Font ──────────────────┐│││
  ├─ Network ────────────────┐│││
  ├─ JavaScript ────────────┐│││
  └─ Platform ──────────────┐│││

Component Overview

Component Purpose Status Key Features
Parser HTML/CSS parsing ✅ Core Tree building, error recovery
DOM Document structure ✅ Core Tree navigation, attributes
Style CSS processing ✅ Core Cascade, inheritance, specificity
Layout Positioning & sizing ✅ Core Box model, block/inline layout
Paint Rendering ✅ Core Drawing, text, stacking contexts
Font Typography ✅ Working Font loading, metrics, glyphs
Network HTTP requests ✅ Working Caching, timeouts, redirects
JavaScript Scripting 🚧 Planned Engine integration, DOM APIs
Browser Application UI ✅ Working Window, events, rendering loop
Platform OS abstraction ✅ Working Windows support, macOS/Linux planned

Frequently Asked Questions

General Questions

Q: What is Grob? A: Grob is an open-source web browser engine written in Rust, focusing on modularity, safety, and performance. See Architecture.

Q: How does it work? A: HTML is parsed into a DOM, CSS styles are applied, layout is calculated, and finally everything is painted to pixels. See the Core Pipeline above.

Q: Why Rust? A: Rust provides memory safety without garbage collection, preventing entire classes of bugs while maintaining high performance.

Component-Specific

Q: Where is HTML parsing handled? A: Parser module - specifically the HTML parser sub-module.

Q: How are fonts loaded? A: Font module - loads from system directories and web sources, with caching.

Q: How does styling work? A: Style module - implements CSS cascade, specificity, and inheritance rules.

Q: How are elements positioned? A: Layout module - calculates positions using the CSS box model.

Q: How is content drawn? A: Paint module - converts layout into rendering instructions, handles stacking.

Q: How are web pages fetched? A: Network module - handles HTTP requests, caching, and resource loading.

Q: How does JavaScript work? A: JavaScript module - integrates a JS engine and provides DOM APIs (in development).

Development

Q: How do I add a new CSS property? A: Modify the Style module to recognize and handle the property in the cascade and inheritance logic.

Q: How do I add support for a new HTML element? A: The parser already handles HTML generically - style and layout handle elements via attributes/types.

Q: How do I port to a new platform? A: Implement the Platform module abstraction for the target OS.

Q: Where should I look to fix a rendering bug? A: Start with Paint module for visual issues, Layout module for positioning problems.

Contributing & Development

Adding Features

Before starting:

  1. Review Architecture to understand where your feature belongs
  2. Check the relevant component's documentation
  3. Understand the module's current limitations

Common tasks:

  • New CSS property: Modify Style
  • New layout mode: Extend Layout
  • New rendering feature: Update Paint
  • Font handling improvement: Enhance Font
  • Network enhancement: Extend Network

Code Organization

grob/
├── browser/              # Browser application
│   └── src/main.rs      # Entry point, event loop
│
├── engine/              # Core rendering engine
│   └── src/
│       ├── parser/      # HTML and CSS parsing
│       ├── dom/         # Document structure
│       ├── style/       # CSS processing
│       ├── layout/      # Positioning engine
│       ├── paint/       # Rendering
│       ├── font/        # Typography
│       ├── network/     # HTTP requests
│       ├── js/          # JavaScript integration
│       └── platform/    # OS abstraction
│
└── documentation/       # This documentation

Testing

  • Unit tests in individual modules
  • Integration tests for component interactions
  • Property-based tests for algorithms

Roadmap & Future Work

Short Term

  • Complete JavaScript engine integration
  • Add Flexbox layout support
  • Implement Grid layout
  • Add more CSS selector support
  • Improve error messages

Medium Term

  • Grid layout system
  • CSS animations and transitions
  • Improved image support
  • Better performance optimizations
  • HTTPS/TLS support
  • macOS port

Long Term

  • WebAssembly support
  • Service Workers
  • Hardware acceleration (GPU rendering)
  • Multi-tab support
  • Developer tools
  • Plugin system

Component Roadmaps

See individual component docs for specific roadmaps:

Module Documentation Quick Links

Module Purpose Key Classes See Also
Parser Parse HTML/CSS HtmlParser, CssParser Full Docs
DOM Document structure Dom, Node Full Docs
Style CSS processing Style, Stylesheet Full Docs
Layout Positioning LayoutBox, LayoutEngine Full Docs
Paint Rendering PaintInstruction, DisplayList Full Docs
Font Typography FontManager, Font Full Docs
Network HTTP NetworkManager, Request Full Docs
JavaScript Scripting JavaScriptEngine Full Docs
Platform OS abstraction FileSystem, SystemInfo Full Docs
Browser Application Browser, EventLoop Full Docs

Getting Help

Learning Path

For Users

  1. Understand what Grob does
  2. Learn how to build and run it
  3. Try loading a simple HTML page

For Developers - Beginner

  1. Read Architecture.md for overview
  2. Pick one component and read its full documentation
  3. Explore the corresponding source code
  4. Try adding a small test case

For Developers - Intermediate

  1. Understand the complete rendering pipeline
  2. Study 2-3 interconnected modules
  3. Trace code through a real scenario (e.g., "loading a page")
  4. Try implementing a simple feature

For Developers - Advanced

  1. Review Architecture.md and all component docs
  2. Understand performance characteristics and trade-offs
  3. Plan architectural improvements
  4. Implement significant features or optimizations

Documentation Standards

All documentation in this folder follows these conventions:

  • Markdown format for easy reading and version control
  • Code examples where helpful
  • ASCII diagrams for architecture visualization
  • Consistent structure: Overview → Concepts → Usage → Integration → Limitations
  • Links between related docs
  • Practical examples in component docs

Last Updated: January 22, 2026

For the latest information, see the individual component documentation files above.

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