[nixos] fixing dependencies and building with recent package managers

[chrisheib]

When trying to get a dev environment running for this I ran into a bunch of problems. It seems on linux the main electron app dev only runs on a really narrow set of Ubuntu 20 dependencies, which at this point is already deprecated. When setting up a nix shell to develop this, there where multiple problems I tried solving.

Firstly npm i didn't want to run because electron-overlay-window v3 depends on a hopelessly outdated (and insecure) version of electron and napi. When trying to install electron with any kind of modernish package management it always defaults to newer versions, which have a different API in napi_create_buffer, which required a patch to the electron-overlay-window module:

-  status = napi_create_buffer(env, size, &img_data, &img_buffer);
+  status = napi_create_buffer(env, size, (void **)&img_data, &img_buffer);

Applying this requires a few extra steps:

cd main
npm i --ignore-scripts
npm i -D patch-package
npx patch-package
npm i

This should probably be fixable in a better way by upgrading to electron-overlay-window v4.

On Nixos it's not easily possible to use the bundled electron, so I needed to use the one from nixpkgs.
This one doesn't get recognized by node out of the box, so I needed to add a small dynamic wrapper to the nix shell hook to create a electron script that includes the shell dependency libraries:

    #!/usr/bin/env bash
    export LD_LIBRARY_PATH=${pkgs.lib.makeLibraryPath buildInputs}
    exec "${pkgs.electron}/bin/electron" "$@"

Afterwards add that script location as env var ELECTRON_BINARY, and change the main/build/script.mjs to reference it instead of the bundled electron:

const electronRunner = (() => {
  let handle = null
  return {
    restart() {
      const electronBin = process.env.ELECTRON_BINARY ?? 'electron'
      console.info(`Restarting Electron process. ${electronBin}`)

      if (handle) handle.kill()
      handle = child_process.spawn(electronBin, ['.'], {
        stdio: 'inherit'
      })
    }
  }
})()

Full working environment is in my fork: chrisheib@39347bc