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Building and Running

This page walks through setting up a local RemixWarp editor build. The examples use scratch-gui because that is where most development happens, but the same clone-and-link pattern applies to the other engine packages.

Prerequisites​

  • Git
  • Node.js v20 (v18 or later is likely fine, but v20 is what we develop against)
  • pnpm, the package manager scratch-gui uses

Building the editor can use several gigabytes of disk space and memory, so give it room.

Clone the packages side by side​

The engine packages link to each other by relative path, so they must be siblings in one parent directory.

mkdir bilup
cd bilup
git clone https://github.com/RemixWarp/scratch-gui
git clone https://github.com/RemixWarp/scratch-vm
git clone https://github.com/RemixWarp/scratch-blocks
git clone https://github.com/RemixWarp/scratch-render
git clone https://github.com/RemixWarp/scratch-paint

You only need the packages you intend to change. If you are just modifying the editor UI, scratch-gui alone is enough; its dependencies fall back to the versions pinned in package.json.

From scratch-gui:

cd scratch-gui
pnpm install
pnpm run link

pnpm run link symlinks the sibling checkouts into scratch-gui:

pnpm link ../scratch-vm ../scratch-blocks ../scratch-render ../scratch-paint

After linking, changes you make in those packages are picked up by the scratch-gui build. If installing after linking ever resets the links, just run pnpm run link again. There is also a pnpm run reinstall script that wipes node_modules and the lockfile, reinstalls, and re-links in one step.

Run the development server​

pnpm start

This starts webpack-dev-server. Open http://localhost:8601/. The dev server also mirrors the production routing, so /editor is the editor, /embed.html is the embed player, and the community client routes are served too.

Production build​

NODE_ENV=production pnpm run build

pnpm run build cleans the build/ and dist/ directories and runs webpack. Setting NODE_ENV=production produces a minified, deployable build under build/.

Linting and formatting​

pnpm run lint   # eslint check
pnpm run fmt    # eslint --fix

Linting must pass before a pull request is merged. See Contributing for the style rules that are not caught automatically (no code comments, no emdashes).

Other packages​

scratch-vm​

scratch-vm uses npm and its own scripts:

cd scratch-vm
npm install
npm run lint
npm run tap          # all tests
npm run tap:unit     # unit tests only
npx tap test/unit/<file>.js   # a single file

scratch-blocks​

Edits under scratch-blocks core/ are compiled with Google Closure, so a plain rebuild is not enough. With node_modules/.bin on your PATH, run:

node universal-python.js build.py

Any new symbols you add must be exported in the goog.global block, or Closure will strip them from the build.

mistwarp-api​

The community backend is an OSL service. With the OSL interpreter installed:

cd mistwarp-api
osl run main.osl   # listens on port 5610

It stores data as flat JSON under data/ and falls back to a local data/blobs/ directory for project files with no additional configuration, so you can run it without any cloud setup.

See also​