Introduction

Ori is a local-first, virtualized note editor built on three independent pillars:

Y.Doc          →  canonical document state (block-based CRDT)
Pretext        →  text layout & measurement (line breaks, caret, hit-testing)
Virtualization →  only the blocks in the viewport ever become DOM

Long notes stay fully editable and syncable while the DOM stays tiny. Layout is derived, never stored — it is recomputed from content, width and typography.

Y.Doc   = canonical app state
DOM     = rendered view (viewport only)
Pretext = derived / cache-only layout

The core is framework-agnostic. React is the first binding; the same EditorController can drive Vue, Svelte, Solid, or a canvas renderer.

Why

• Local-first. Every keystroke is a Yjs update — persist it, sync it, undo it. No server required.
• Scales. Thousands of blocks, a few dozen DOM nodes. Heights come from Pretext; windowing from a binary-searched height map.
• Extensible. Register custom, measurable nodes — block types (image, divider) and inline atoms (@mention) — with a measure function and a renderer.
• Honest layout. Pretext measures with the same font the browser paints, and lines are materialized so the browser never re-wraps and disagrees.

Next steps

• Getting started — install and render an editor.
• Architecture — how Y.Doc, Pretext and the virtualizer fit.
• Extensibility — add your own measurable nodes.