$ show Hufe921/canvas-editor
This repository is a production-grade, canvas-based WYSIWYG rich text document editor published as the npm package `@hufe921/canvas-editor`. It is a monolithic library that provides a fully self-contained document editing experience, rendering text, tables, images, LaTeX, and form controls entirely on an HTML `<canvas>` element. The architecture is a well-structured layered design featuring a Command pattern facade (`Command`/`CommandAdapt`), a custom particle-based rendering engine (`Draw`), a pub/sub event system (`EventBus`), and a plugin system. The editor supports a wide array of features including pagination, headers/footers, watermarks, change tracking (trace mode), macros, spell checking, accessibility, multi-column layouts, and a sophisticated cascade expression engine for dynamic form control behavior. It is specifically designed for high-fidelity document editing in domains like Electronic Medical Records (EMR), contracts, and official documents, as evidenced by the mock data and feature set. The codebase demonstrates strong engineering craftsmanship. Several components are genuinely reusable, including a custom Myers O(ND) diff algorithm, a standalone LaTeX-to-SVG renderer using Hershey fonts, a fully featured DSL expression evaluator for control cascading, and a clean event bus implementation. The project is actively maintained with a comprehensive test suite (Cypress E2E, Vitest unit tests), modern tooling (Vite, TypeScript), and a rich plugin ecosystem. While some core files like `Draw.ts` and `CommandAdapt.ts` are large and exhibit tight coupling, the overall architecture, separation of concerns, and quality of the reusable components are well above average.
The LLM identified 6 files worth highlighting for reuse:
A fully custom DSL for defining dynamic control behavior (hide, required, disabled, compute). It includes a tokenizer, recursive descent parser, and evaluator supporting arithmetic, string functions, date operations, and `getValue(@self)`. Completely self-contained and extractable for any form engine or rule-based system.
Implements the Myers O(ND) diff algorithm with linear-space divide-and-conquer. Provides hierarchical text diff (line + character) and anchor-based element comparison for structured documents. The core diff logic is a self-contained algorithm, while the element comparison layer is tailored to the editor's data model.
Converts LaTeX expressions to SVG/PDF paths using a custom Hershey font parser. Includes a comprehensive symbol definition file (`symbols.ts`) and font data (`hershey.ts`). A highly specialized, self-contained component that could be extracted for math rendering in any canvas or SVG application.
A clean, typed, generic pub/sub event bus implementation. Provides `on`, `off`, and `emit` methods with strong typing for event names and payloads. Self-contained and directly reusable in any TypeScript project for decoupled communication.
A stack-based undo/redo manager with a configurable maximum record count. Provides `record`, `undo`, `redo`, `canUndo`, `canRedo`, and `clear` methods. A self-contained utility class implementing a standard pattern cleanly.
Orchestrates multiple Web Workers for offloading CPU-intensive tasks (word count, catalog generation, group IDs, value export). Provides a clean abstraction over Worker lifecycle, message passing, and result collection. The orchestration pattern is reusable, though the specific worker tasks are tied to the editor's domain.