Wires the web process extension into the kiosk browser's command line.

There is no process and no supervision tree here — the whole runtime lives in the web process extension that Cog loads. This module answers three questions and nothing else: where the .so is, which directories it should scan, and what the device wants configured.

Usage

Merge two things into however you already start the browser — browser_args/0 for the command line, browser_env/1 for the environment:

args = ["--platform=drm", url] ++ Myelin.browser_args()
env = [{"XDG_RUNTIME_DIR", runtime_dir}] ++ Myelin.browser_env()

MuonTrap.Daemon.start_link("cog", args, env: env)

Scripts are read once, when the web process starts, so changes take effect after Cog restarts.

Nothing runs until you ask for it

The scripts that ship with this library are in bundled_dir/0, which is already on the search path — but every one of them is dormant. Switching one on is a line of configuration, and that is the whole install:

config :myelin,
  scripts: %{
    "keyboard" => %{enabled: true},
    "screensaver" => %{enabled: true}
  }

Copy one into your own application only when you want to change it — mix myelin.copy keyboard — and the copy replaces the shipped version, because later entries on the search path win.

Configuration

Two things are set per device, both read from your application's config:

config :myelin,
  trusted_origins: ["http://localhost:4000"],
  scripts: %{"screensaver" => %{enabled: true, idle: 300}}

The keys under scripts are directory names.

trusted_origins decides where <meta name="myelin-…"> tags may configure anything. It starts empty, so on a page you have not listed the device configuration is the only thing that counts — which is the point on a kiosk that visits pages you do not control.

Both travel to the extension in MYELIN_CONFIG. That is not a flourish: the extension runs in Cog's web process, not on the BEAM, so it cannot call Application.get_env/2. A file or the process environment are the only two channels, and a file would mean writing one at boot.