Expresso.Watch (expresso v0.1.0)

Serves a deck, and renders it again after each change

$ mix expresso deck.exs [deck.html] --watch [--port 4100]

Open http://127.0.0.1:4100/ in a browser. After each change to the deck file, or to an image, a diagram or a style sheet of the deck, the watch mode renders the deck again. The page then reloads, and it shows the same step. With an output path, the watch mode also writes the document to that file.

When a render fails, the watch mode writes the error to the standard error. The page then keeps the last good document, and the output file does not change. Stop the watch mode with Ctrl-C.

Four modules do the work:

Expresso.DeckFile records the files that each render reads.
Expresso.Watch.Files finds a change to one of those files.
Expresso.Watch.Server serves the page, and makes it reload.
Expresso.Element.Diagram.Cache keeps the SVG of each graph from one render to the next, so a change does not run each tool of the deck again.

The section "The watch mode" of docs/architecture.md gives the design, and the parts that a later version can replace.

Summary

Functions

run(input_path, output_path, options)

Run the watch mode for a deck file

Functions

run(input_path, output_path, options)

@spec run(Path.t(), Path.t() | nil, keyword()) :: {:error, String.t()}

Run the watch mode for a deck file

The function returns only for an error that stops the watch mode, such as a port in use. It writes the error message to the standard error, and it returns {:error, message}.

The options are:

:port - the port of the server. This option is required. The port 0 gives a free port.
:interval - the time between two snapshots of the files, in milliseconds. The default is 500.
:device and :error_device - the devices for the messages and for the errors. The defaults are :stdio and :stderr.
:notify - a process that gets {Expresso.Watch, event} for each event: {:serving, url}, {:rendered, version} or {:failed, message}. The tests wait for these messages.