nimforum mirror - Catching shell resizes (asynchronously?)

xioren (orginal) [2021-05-26T15:50:44+02:00] view original

I have a program that outputs continuously to the terminal (think cmatrix) and I need to immediately catch terminal resizes to reset the output, but cant figure out how to do it properly. I need something to the effect of:

while true:
  if terminalWasResized():
    break
  synchronousProc()

I have tried making terminalWasResized async but it ends up blocking and I can't make the synchronous proc async because it won't compile (memory safety warnings). The synchronous proc also takes some time to complete so I can't wait on it before checking terminal size again.

Any ideas?

codic12 (orginal) [2021-05-31T08:00:19+02:00] view original

You can use a background thread but polling the size is the wrong approach, and will eat up lots of resources. Better to listen for SIGWINCH though I'm not quite sure how standardized it is

PMunch (orginal) [2021-05-31T09:22:46+02:00] view original

Never heard of SIGWINCH before, but it seems to work at least in my URxvt terminal:

import posix

type
  StdSignal* = enum
    SIGHUP = 1       ##  1. Hangup
    SIGINT           ##  2. Terminal interrupt signal

# https://gist.github.com/dom96/908782
template onSignal*(sigs: varargs[StdSignal]; actions: untyped): untyped =
  # https://www.gnu.org/software/libc/manual/html_node/Sigaction-Function-Example.html#Sigaction-Function-Example
  proc newHandler(signum: cint) {.noconv.} =
    echo "\n[Error] Standard signal " & $StdSignal(signum) & " detected"
    `actions`
  
  var
    newAction: SigAction
  newAction.sa_handler = newHandler
  discard sigemptyset(newAction.sa_mask)
  newAction.sa_flags = 0
  
  for sig in sigs:
    discard sigaction(cint(sig), newAction, nil)

when isMainModule:
  onSignal(SIGFPE, SIGINT):
    quit()
  
  echo "Hit Ctrl-C to end this program .."
  discard pause()

cblake (orginal) [2021-05-31T12:50:08+02:00] view original

SIGWINCH is ancient and well supported on any OS "xterm" (meaning probably X windows) runs on natively. If you look at the code for xterm/screen.c you will see there is no big #ifdef circus around SIGWINCH. Variation in library/OS code around EINTR/EAGAIN is much greater. See here at the bottom by "Interruption of" for some details on that.

xioren (orginal) [2021-06-01T18:58:27+02:00] view original

SIGWINCH looks promising, thank you.

JPLRouge (orginal) [2021-06-03T10:15:29+02:00] view original

change

  /etc/X11/app-defaults/XTerm
 *allowWindowOps: true
 *eightBitInput: false

with escape codes

example in https://github.com/AS400JPLPC/nim_termkey/blob/master/termkey.nim

Mirror of forum.nim-lang.org

8040 :: Catching shell resizes (asynchronously?)