Node Lynx

Node Lynx

Use node-lynx as a local Lynx runtime for screenshots, preview windows, smoke tests, DebugRouter OpenCard sessions, and automation that needs to inspect or interact with a rendered Lynx page from Node.js.

Default sample template URL:

https://lynxjs.org/lynx-examples/gallery/dist/GalleryComplete.lynx.bundle

CLI

Prefer the CLI for one-off screenshots, quick template validation, and simple preview sessions.

Show available options:

node-lynx --help

Capture a headless screenshot and exit:

node-lynx render \
  "https://lynxjs.org/lynx-examples/gallery/dist/GalleryComplete.lynx.bundle" \
  --width 268 \
  --height 469 \
  --dpr 2 \
  --output ./gallery.png \
  --timeout 30000 \
  --screenshot-delay 500 \
  --no-debug-router

Render a local bundle:

node-lynx render \
  --template ./dist/main/template.js \
  --width 390 \
  --height 844 \
  --output ./node-lynx-local.png \
  --no-debug-router

Open a visible preview window on macOS:

node-lynx preview \
  "https://lynxjs.org/lynx-examples/gallery/dist/GalleryComplete.lynx.bundle" \
  --width 268 \
  --height 469 \
  --dpr 2 \
  --title "Node Lynx Preview"

Start a DebugRouter-backed session without an initial template:

node-lynx render

CLI rules:

• Use render for headless screenshots and automation.
• Use preview only on macOS; it creates an AppKit window.
• Use --template <path> for local bundles and --url <url> for remote bundles. A positional http:// or https:// input is treated as a remote bundle URL.
• Use --width and --height as CSS pixel viewport values.
• Use --dpr or --device-pixel-ratio to control output scale; the PNG pixel size is width * dpr by height * dpr.
• Use --timeout <ms> for bundle download, template load, CDP calls, and first frame submission timeouts.
• Use --screenshot-delay <ms> to wait after the first frame before capture. This defaults to 100; use a larger delay for image-heavy or network-heavy pages.
• Pass --no-debug-router for CI or one-shot screenshot commands that should exit immediately after writing the PNG.
• Omit --no-debug-router when you need DebugRouter/OpenCard. Without an initial template, render waits for DebugRouter OpenCard. preview also waits for OpenCard without creating an initial window.

TypeScript API

Prefer the API when the task needs programmatic setup, repeated captures, global props, CDP calls, input simulation, or custom lifecycle handling.

Import from the node-lynx package declared by the target project. For public npm usage this is typically:

import { HeadlessLynxView } from '@lynx-js/node-lynx';

Render a remote template to PNG:

import { writeFile } from 'node:fs/promises';
import { HeadlessLynxView } from '@lynx-js/node-lynx';

const templateUrl =
  'https://lynxjs.org/lynx-examples/gallery/dist/GalleryComplete.lynx.bundle';

const view = new HeadlessLynxView({
  width: 268,
  height: 469,
  devicePixelRatio: 2,
  timeoutMs: 30000,
});

try {
  await view.loadTemplateFromUrl(templateUrl, {
    initialData: { source: 'node-lynx' },
    globalProps: { theme: 'light' },
  });
  const png = await view.screenshot({ settleMs: 500 });
  await writeFile('./gallery.png', png);
} finally {
  view.destroy();
}

Render a local bundle buffer. Always pass a file URL so relative resources have the right base URL:

import { readFile, writeFile } from 'node:fs/promises';
import { resolve } from 'node:path';
import { pathToFileURL } from 'node:url';
import { HeadlessLynxView } from '@lynx-js/node-lynx';

const templatePath = resolve('./dist/main/template.js');
const view = new HeadlessLynxView({ width: 390, height: 844 });

try {
  await view.loadTemplate(await readFile(templatePath), {
    url: pathToFileURL(templatePath).href,
  });
  await writeFile('./node-lynx-local.png', await view.screenshot());
} finally {
  view.destroy();
}

Inspect the DOM through CDP:

const responseText = await view.invokeCDPFromSDK(
  JSON.stringify({
    id: 1,
    method: 'DOM.getDocument',
    params: { depth: -1, pierce: true },
  })
);
const response = JSON.parse(responseText);

Update runtime data after load:

view.updateData({ selected: true });
view.updateGlobalProps({ locale: 'en-US' });
await view.waitForFrame();

Windowed API

Use WindowedLynxView only on macOS when a visible app window is required.

import { WindowedLynxView } from '@lynx-js/node-lynx';

const view = new WindowedLynxView({
  width: 268,
  height: 469,
  devicePixelRatio: 2,
  title: 'Node Lynx Preview',
});

try {
  await view.loadTemplateFromUrl(
    'https://lynxjs.org/lynx-examples/gallery/dist/GalleryComplete.lynx.bundle'
  );
  await view.waitForFrame();
  view.click(20, 70);
  view.typeText('hello from node-lynx');
  view.pressKey('Enter');
  await view.waitUntilClosed();
} finally {
  view.destroy();
}

Interaction APIs use CSS pixel coordinates. Supported pressKey values are Backspace, Delete, Enter, ArrowLeft, ArrowRight, ArrowUp, and ArrowDown.

DebugRouter OpenCard

Use OpenCard managers when the page should be opened by DebugRouter instead of an initial CLI/API template load.

import {
  HeadlessOpenCardManager,
  LynxEnv,
  WindowedOpenCardManager,
} from '@lynx-js/node-lynx';

LynxEnv.init();
LynxEnv.setAppInfo(['App', 'AppVersion'], ['NodeLynxSkill', '1.0.0']);

const Manager =
  process.platform === 'darwin' ? WindowedOpenCardManager : HeadlessOpenCardManager;

const manager = new Manager({
  view: { width: 268, height: 469, devicePixelRatio: 2, timeoutMs: 30000 },
  onCardLoaded(card) {
    console.log(`opened ${card.url}`);
  },
  onCardError(error, card) {
    console.error(`failed ${card.url}: ${error.message}`);
  },
});

manager.install();

process.once('SIGINT', () => {
  manager.dispose();
  process.exit(0);
});

Operational Notes

• Prefer a real remote template URL when the bundle loads URL-relative resources.
• Treat waitForFrame() as "a frame was submitted", not as proof that every image or network resource has decoded.
• Use screenshot({ settleMs }) or CLI --screenshot-delay for pragmatic post-frame settling. Prefer a page-level ready signal when the page exposes one.
• Always call destroy() in a finally block for each view.
• Keep examples and troubleshooting scoped to node-lynx usage. Do not add internal package names, internal registries, or private distribution details to this open-source-facing skill.