Running your app on a computer

You can run a nest_gen2 app on your own computer instead of the Nest, and see its screen in a browser. It's for developing and testing screens: change the code, restart, look, without building for the Nest or deploying.

The app runs unchanged. With target: :host the SDK starts as usual but touches no hardware (architecture.html draws both side by side):

The screen still goes to sleep after the idle timeout, as on the Nest; the viewer shows it dimmed. Press the ring or "Walk past" to wake it.

Network fetches are real: an app that fetches bus times fetches real bus times.

One-time setup

1. A C compiler (cc, e.g. from build-essential or Xcode's command-line tools). In your app's folder run:

   mix nest_gen2.host

   It builds the text renderer for your computer into ~/.nest_gen2_sdk/bin and checks the fonts.

2. The fonts. The SDK draws text with Nest's own Akkurat fonts, which are commercially licensed, so they don't ship with the SDK. Copy them from your own Nest (while it's awake, i.e. with the screen on):

   mkdir -p ~/.nest_gen2_sdk/fonts
   for f in AkkuratNest-Bold.ttf AkkuratNest-Regular.ttf; do
     ssh root@<nest-address> "cat /nestlabs/share/fonts/$f" > ~/.nest_gen2_sdk/fonts/$f
   done

   Any TrueType font works too if you give it those names, or set config :nest_gen2, font_dir: "/path/to/fonts".

Running

Run your app with the SDK told it's on a computer, e.g.:

elixir --erl "-nest_gen2 target host" -S mix run --no-halt

or in your app's config/dev.exs:

config :nest_gen2, target: :host

Then open http://localhost:4000. Turn the ring with the mouse wheel over it, by dragging, or with ← and →; click it, or press Space, to press it. The buttons give a double click, a long press and someone walking past.

Use the same Erlang/Elixir as for the Nest (platform/host_env.sh), or any newer one: on the host nothing has to load on the Nest.

From another computer

The viewer listens only on this computer (127.0.0.1). To see it from, say, a laptop that can reach this computer over SSH (Tailscale works), forward the port and open http://localhost:4000 on the laptop:

ssh -L 4000:localhost:4000 <this-computer>

Or listen on another address with config :nest_gen2, host_viewer_ip: {0, 0, 0, 0}. Then anyone who can reach that port can press your app's buttons, so keep it to a trusted network.

Showing it publicly

To put the screen on a public website, make the viewer watch-only:

config :nest_gen2, host_viewer_controls: false

The page then has no buttons and ignores the mouse and keyboard, and the viewer refuses every press, turn and climate change (403), so visitors can't drive your app or each other's view: everyone sees the same screen. Your app has to move between its screens by itself. Replies may be kept for a second by a cache in front, such as a CDN, and the screen is only encoded when it changes, so many visitors cost about the same as one.

Run it behind a reverse proxy or tunnel that adds HTTPS; the viewer itself speaks plain HTTP.

Settings

To start from the settings your Nest has, copy its storage across (leave out anything secret you'd rather not have on the computer):

mkdir -p ~/.nest_gen2_sdk/data/<app>
ssh root@<nest-address> "cd /media/scratch/.nest_gen2_sdk/data/<app> && tar cf - *.term" |
  tar xf - -C ~/.nest_gen2_sdk/data/<app>

From code and tests

NestGen2.Host drives the simulated hardware: turn/1, step/1, click/0, double_click/0, long_press/0, motion/1, climate/2, and screenshot/0 for the screen as a PNG. They produce the same events as the real hardware. The viewer's endpoints do the same over HTTP, for scripts:

curl -o screen.png http://localhost:4000/screen.png
curl -X POST "http://localhost:4000/step?dir=cw"
curl -X POST http://localhost:4000/click

NestGen2.Display.snapshot/0 works on the Nest too: it returns what the screen shows.