Saturday 21 March 2020

Working with ttystudio and ttyrec

The best of all the tty to animated gif converters, is ttystudio because it outputs small gifs.

Sadly it is slow, and uses up way to much memory -- even running out of memory for even a small session.

Ironically it boasts of not using imagemagick while requiring node! No wonder it runs out of memory. Sadly the frams also seem to be based on clock time instead of ttyrec frames.

Even worse, it only works for recording live sessions.

This shell script causes ttystudio to convert a ttyrec file.

Use: ./ttyrec2studio ttyrecfilename
to make ttyrecfilename.gif

#! /bin/bash
ttystudio() {
  local ttyrec="$1"
  local fifo=$(mktemp -u)
  mkfifo "$fifo"

  coproc ttypipe { SHELL=$(realpath "$0") QUITPIPE="$fifo" TTYPLAYFILE="$ttyrec" command ttystudio "$ttyrec.gif" >/dev/tty 2>&1 ; }

  # when we've finished with fifo, ttyplay has finished
  cat "$fifo"
  # send ^Q
  printf $'\x11' >/proc/$$/fd/${ttypipe[1]}
  # close pipe to coproc
  eval "exec ${ttypipe[1]}<&-"
  # Drain pipe from coproc
  #eval "exec ${ttypipe[0]}<&-"
  eval "cat /proc/$$/fd/${ttypipe[0]}"
  wait $! # is coproc
  echo Done all $?

emit() {
  rm -f "$QUITPIPE"
  echo "Playing $1" >&3
  ttyplay "$1"
  echo "Finished playing $1 [$?]" >&3

main() {
  if test -z "$QUITPIPE"
  then ttystudio "$@"
  else emit "$TTYPLAYFILE"

main "$@"

It works by tricking ttysudio to re-invoke itself as the shell for what would have been the interactive subshell. As arguments can't be passed to the subshell, it smuggles them as environment variables.

When invoked as the subshell it simply uses ttyplay to re-play the ttyrec file.