The one process that writes a session's terminal, for Drafter.Compositor.

{:ok, writer} = Drafter.Render.Writer.start_link(:tty)
Drafter.Render.Writer.write(writer, text_rows)
Drafter.Render.Writer.write_image(writer, image_bytes)

Every write is one call to the sink, in the order the calls were made, so no sequence is ever cut by another, and neither call blocks the caller. write/2 is for text and control sequences and is never dropped; behind?/1 tells whether any of it is still unwritten, for a caller that would rather merge its next frames into one than queue them. write_image/2 is for a frame's image bytes: while the terminal is slow to accept one, a newer image that has arrived by the time an older one's turn comes replaces it, so the terminal sees the latest picture and no backlog.

The sink is a function of iodata, or {:tty, fallback} to write /dev/tty — which the writer opens itself, since a raw file is usable only by the process that opened it — using the fallback function when /dev/tty cannot be opened.