Canopy in April 2026 — Highlights
A two-minute summary of a month of work. For the day-by-day version, see the Japanese original.
Canopy is a structure editor written in MoonBit: it treats source code as structure (IR) rather than strings, with text kept as the source of truth. Concurrent editing is built on a CRDT implementing the eg-walker paper. Around it sit a few sibling projects: Loom (incremental parsing), incr (incremental computation), and js_engine (a JS interpreter validated against test262).
1. One protocol for every editor surface
Ideal editor and the ProseMirror example both moved onto a single EditorProtocol, with CM6Adapter/PMAdapter formalizing the adapter layer. Instead of each editor surface having its own bespoke wiring, they now all speak the same language to the underlying document model.
2. The pretty-printer meets the DOM
The Wadler-Lindig pretty-printer’s output now bridges to ViewNode, wired up to real HTML syntax highlighting — turning what had been a text-formatting tool into part of the rendering pipeline.
3. Markdown gets a real block editor
Markdown became a first-class editing target: seven Markdown edit operations, a three-mode web editor, a block-input textarea overlay, and a semantic-HTML preview adapter all shipped, alongside Phase 2 and 3 of a “Container” abstraction (text sync, block-doc sync, document-level undo grouping) that treats documents as block-addressable.
4. A generic B-tree and a confidence layer
lib/btree was carved out as a standalone generic B-tree library and merged with March’s order-tree work, gaining range-delete and splice-promotion chain repair. Separately, lib/semantic introduced a confidence lattice and symbolic annotator — the first infrastructure for reasoning about how sure the system is about an inferred result rather than treating everything as certain.
5. Language decoupling begins
LanguageCapabilities[T] split Lambda-specific types out of SyncEditor, opening the door to generic tree operations that don’t assume Lambda is the only language in the room — groundwork that pays off later when JSON, Markdown, and eventually JSX need the same editor machinery.
6. Drag-and-drop, E2E tests, and workspace tooling
Drag-and-drop foundations landed in both Ideal and the block editor (semantic Before/After drops, grip-only drag, outline DnD), Web E2E tests for Lambda/JSON editors joined CI, loom retired ReactiveParser in favor of a unified @loom.Parser[T], and moon.work workspace tooling arrived with CI-enforced dependency-direction rules.
By the end of April, Canopy had the shape it would keep for months: a language-agnostic core, block-addressable documents, and a growing set of adapters rather than one hardcoded editor.
- GitHub: dowdiness/canopy · dowdiness/loom · mooncakes.io/user/dowdiness
- Full log: April 2026 devlog (Japanese)