mathnotes-app/mobile-ink

Mobile Ink is a drawing engine for React Native mobile apps, extracted from the MathNotes note-taking app and released as an open-source library. It solves a specific hard problem: building a high-performance, infinite-scrolling handwriting surface on iOS and Android that handles Apple Pencil input, pressure sensitivity, zoom, momentum scrolling, and long notebooks without freezing the app. The library provides a set of building blocks. At the core is a native drawing canvas backed by Skia (a graphics library) and Metal (Apple's GPU rendering system), which keeps drawing fast at the hardware level rather than relying on JavaScript. A continuous engine pool manages a fixed set of native canvas instances and swaps them in and out as you scroll through a long notebook, avoiding the memory cost of creating one canvas per page. On top of these primitives sits a ready-made infinite notebook component that handles page creation, serialization (saving strokes as JSON), zoom, and background types like grid or ruled lines. You would use this if you are building a React Native app that needs serious handwriting or drawing support, such as a note-taking app, a whiteboard, or a math editor, and you do not want to rebuild the tricky native rendering stack yourself. It currently runs in production in the MathNotes iOS app. The stack is C++ at the drawing engine level, with React Native and TypeScript for the JavaScript interface. Both iOS and Android are supported. The full README is longer than what was provided.