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Scrattino3 Desktop is a programming environment based on Scratch 3.0

Developer Instructions

Prepare scratch-gui

This step is temporary: eventually, the scratch-desktop branch of the Scratch GUI repository will be merged with that repository's main development line. For now, though, there's a separate branch:

  1. Clone the scratch-gui repository if you haven't already.
  2. Switch to the scratch-desktop branch with git checkout scratch-desktop
  3. Build with BUILD_MODE=dist and STATIC_PATH=./static:
    • macOS, WSL, or Cygwin: run BUILD_MODE=dist;STATIC_PATH=./static npm run build or BUILD_MODE=dist;STATIC_PATH=./static npm run watch
    • CMD: run set BUILD_MODE=dist & STATIC_PATH=./static once, then npm run build or npm run watch any number of times in the same window.
    • PowerShell: run $env:BUILD_MODE = "dist"; $env:STATIC_PATH = "./static" once, then npm run build or npm run watch any number of times in the same window.
  4. Link cloned scratch-gui by npm link in the cloned scratch-gui.
  5. Set scratch-desktop to use linked scratch-gui by 'npm link scratch-gui'.

Prepare media library assets

In the scratch-desktop directory, run npm run fetch. Re-run this any time you update scratch-gui or make any other changes which might affect the media libraries.

Run in development mode

npm start

Make a packaged build

npm run dist

Node that on macOS this will require installing various certificates.

Signing the NSIS installer (Windows, non-store)

This section is relevant only to members of the Scratch Team.

By default all Windows installers are unsigned. An APPX package for the Microsoft Store shouldn't be signed: it will be signed automatically as part of the store submission process. On the other hand, the non-Store NSIS installer should be signed.

To generate a signed NSIS installer:

  1. Acquire our latest digital signing certificate and save it on your computer as a p12 file.
  2. Set WIN_CSC_LINK to the path to your certificate file. For maximum compatibility I use forward slashes.
    • CMD: set WIN_CSC_LINK=C:/Users/You/Somewhere/Certificate.p12
    • PowerShell: $env:WIN_CSC_LINK = "C:/Users/You/Somewhere/Certificate.p12"
  3. Set WIN_CSC_KEY_PASSWORD to the password string associated with your P12 file.
    • CMD: set WIN_CSC_KEY_PASSWORD=superSecret
    • PowerShell: $env:WIN_CSC_KEY_PASSWORD = "superSecret"
  4. Build the NSIS installer only: building the APPX installer will fail if these environment variables are set.
    • npm run dist -- -w nsis

Make a semi-packaged build

This will simulate a packaged build without actually packaging it: instead the files will be copied to a subdirectory of dist.

npm run dist:dir


You can debug the renderer process by opening the Chromium development console. This should be the same keyboard shortcut as Chrome on your platform. This won't work on a packaged build.

You can debug the main process the same way as any Node.js process. I like to use Visual Studio Code with a configuration like this:

    "launch": {
        "version": "0.2.0",
        "configurations": [
                "name": "Desktop",
                "type": "node",
                "request": "launch",
                "cwd": "${workspaceFolder:scratch-desktop}",
                "runtimeExecutable": "npm",
                "autoAttachChildProcesses": true,
                "runtimeArgs": ["start", "--"],
                "protocol": "inspector",
                "skipFiles": [
                    // it seems like skipFiles only reliably works with 1 entry :(
                "sourceMaps": true,
                "timeout": 30000,
                "outputCapture": "std"