$ show d2lang/d2
D2 is a declarative diagramming language and compiler implemented in Go. It parses a textual DSL, compiles to an intermediate representation, applies automatic layout via multiple engines (Dagre, ELK, and the custom TALA engine), and renders to SVG, PNG, PDF, PPTX, ASCII art, and animated GIF. The architecture is a pipeline: parser (d2parser) → compiler (d2compiler/d2ir) → graph (d2graph) → layout (d2layouts) → renderer (d2renderers). It also includes a language server (d2lsp) for IDE integration and JavaScript/WASM bindings for browser and Node.js usage. The codebase is production-grade with extensive testing, resource safety patterns (work guards, budgets, transactions), security hardening (SVG escaping, network policy), and a CI/CD release pipeline. External dependencies include Go modules for layout algorithms, bundled fonts, and Noto Color Emoji. The system is primarily a CLI tool and Go library, with a secondary JavaScript API.
The LLM identified 5 files worth highlighting for reuse:
Provides fundamental geometry types (Point, Box, Segment, Ellipse) and intersection algorithms. Self-contained and could be extracted for any project needing 2D geometry operations. Demonstrates clean abstractions and efficient algorithms.
Safe SVG element and attribute construction with automatic escaping of untrusted content. Reusable for any Go project that generates SVG output. Demonstrates careful security design to prevent injection attacks.
HTTP client wrapper that enforces public-only network access, blocks private IPs and metadata endpoints, and validates redirects. Reusable for any application needing secure outbound HTTP. Demonstrates defense-in-depth with DNS recheck and redirect validation.
Grid-based spatial index for exact queries (bend collision detection). Generic and could be reused for any 2D spatial query problem. Demonstrates efficient broad-phase filtering with minimal dependencies.
Layered font fallback resolver with byte budgets and scene caching. Handles deterministic emoji resolution via Noto Color Emoji. Reusable for any text rendering system needing fallback fonts. Demonstrates careful resource budgeting and caching to avoid unbounded memory use.