Module @chestnutlabs/gcode-renderer-2d

@chestnutlabs/gcode-renderer-2d

Low-resource Canvas 2D layer renderer for the Chestnut Labs G-code Preview toolpath stack (DD-014 / Epic E8).

An opt-in current/adjacent-layer 2D view over the existing ToolpathIR, for contexts where the default Three.js renderer is a poor fit: old / low-end mobile, embedded printer touchscreens (Fluidd/Mainsail-class UIs), and locked-down or WebGL-blocked browsers. One parse, one IR, a second lightweight view — no second parser path, no three, no framework. Per-segment color is single-sourced with the 3D renderer via @chestnutlabs/gcode-colors, so the two never disagree.

The memory ceiling is the point: drawing is bounded to the active (± adjacent, later phases) layer, never the whole model.

Status: E8 phases 1–3 done. Phase 1 (#212): the Canvas 2D core — draw one layer from the IR, honest color, fit-to-canvas. Phase 2 (#213): current-layer + adjacent "ghost" layers (dimmed preceding layers, adjacentLayers default 1 / floor 0) over one stable model frame. Phase 3 (#214): selectable from the viewer via <GcodePreview renderer="2d" /> (the 3D renderer is loaded on demand, so a 2D-only bundle never ships Three.js), plus a live-progress "completed cut" (setProgress). Still ahead: the low-resource benchmark + capability-honesty UX (#215).

Usage

import { LayerView2D } from '@chestnutlabs/gcode-renderer-2d';

const view = new LayerView2D(canvas, { colorMode: { mode: 'feature', palette, fallback: [0.7, 0.7, 0.7] } });
view.setToolpath(ir); // a ToolpathIR from the worker parser
view.setLayer(12);
view.render(); // clears + redraws the active layer

The drawing core is also exposed as pure functions — drawLayer(ctx, ir, opts), computeLayerFit, layerBounds2D, rgbToCss — which take a minimal Canvas-2D-context interface and are fully testable in Node with a recording mock.

Honesty

A flat per-layer 2D view cannot represent non-XY/CNC toolpaths or 3D-only options. A missing or out-of-range layer draws nothing and reports drawn: false rather than fabricating geometry. Color modes that read an optional IR channel (feature, object, feedrate) must be capability-gated by the caller. The full capability-honesty UX for non-XY / layers: unavailable inputs arrives with the phase-4 work (#215).