### The freewheeling protocol with client apps or a (meta) driver

### The freewheeling protocol with the driver

This app is the driver for freewheeling apps, but it's also itself a
freewheeling app that can be modified live by a meta driver (really just a
copy of itself with a few different filenames for reading/writing messages).

* `live.receive_from_driver()` -- looks for a message from the driver, and
  returns nil if there's nothing.

* `live.send_definition_to_app(state)` -- send an editor buffer's contents to
  the client app as a new definition. Sets `state.load_time_error` if the
  client app encountered an error.

* `live.send_to_driver(msg)` -- sends a message to the driver.

* `live.send_to_app(msg)` -- send a command to the client app. See the
  protocol above for valid commands.

* `live.send_run_time_error_to_driver(msg)` -- sends an error to the driver.
  Automatically invoked by the LÖVE error handler, so you shouldn't need to
  call this.

* `live.receive_from_app()` -- receives a message from the client app,
  returning it or `nil` if no message was received. If the message is an
  error, it's saved to `Load_time_error` and the call returns an empty
  response `''`.

* `live.receive_run_time_error_from_app()` -- checks for any run-time errors
  in the client app, and populates them in `Run_time_error`. Automatically
  invoked, so you shouldn't need to call this.

Primitives for communicating with the meta-driver:

* `live.receive_from_driver()` -- looks for a message from the meta-driver,
  and returns nil if there's nothing.
* `live.send_to_driver(msg)` -- sends a message to the meta-driver.
* `live.send_run_time_error_to_driver(msg)` -- sends an error to the
  meta-driver. Automatically invoked by the LÖVE error handler, so you
  shouldn't need to call this.