Comment by capitainenemo

> then they confidently send me something that breaks on testing it, then half a dozen more iterations, then "python2 is doing the wrong thing or, 'I could get this working but it isn't worth the effort'"

It almost works as-is in my testing. (By the way, there's a typo in the usage message.) Here is my test process:

  #!/usr/bin/env python
  import random, sys, time
  
  
  def out(b):
      # ASCII 0..7 for the second digit of the color code in the escape sequence
      color = random.randint(48, 55)
      sys.stdout.buffer.write(bytes([27, 91, 51, color, 109, b]))
      sys.stdout.flush()
  
  
  for i in range(32, 256):
      out(i)
      time.sleep(random.random()/5)
  
  
  while True:
      out(random.randint(32, 255))
      time.sleep(0.1)

I suppressed random output of C0 control characters to avoid messing up my terminal, but I added a test that basic ANSI escape sequences can work through this.

(My initial version of this didn't flush the output, which mistakenly lead me to try a bunch of unnecessary things in the main script.)

After fixing the `print` calls, the only thing I was forced to change (although I would do the code differently overall) is the output step:

  # sys.stdout.write(out.encode("UTF-8"))
  sys.stdout.buffer.write(out.encode("UTF-8"))
  sys.stdout.flush()

I've tried this out locally (in gnome-terminal) with no issue. (I also compared to the original; I have a local build of 2.7 and adjusted the shebang appropriately.)

There's a warning that `bufsize=1` no longer actually means a byte buffer of size 1 for reading (instead it's magically interpreted as a request for line buffering), but this didn't cause a failure when I tried it. (And setting the size to e.g. `2` didn't break things, either.)

I also tried having my test process read from standard input; the handling of ctrl-C and ctrl-D seems to be a bit different (and in general, setting up a Python process to read unbuffered bytes from stdin isn't the most fun thing), but I generally couldn't find any issues here, either. Which is to say, the problems there are in the test process, not in `ibmfilter`. The input is still forwarded to, and readable from, the test process via the `Popen` object. And any problems of this sort are definitely still fixable, as demonstrated by the fact that `curses` is still in the standard library.

Of course, keys in the `special` mapping need to be defined as bytes literals now. Although that could trivially be adapted if you insist.