Cygwin doesn't handle SIGWINCH properly in Windows Terminal

[Takashi Yano]

On Tue, 16 Feb 2021 09:26:52 -0700
Brian Inglis wrote:
> On 2021-02-16 04:31, Takashi Yano via Cygwin wrote:
> > On Tue, 16 Feb 2021 19:31:54 +0900
> > Takashi Yano wrote:
> >> On Sun, 14 Feb 2021 17:43:58 +0900
> >> Takashi Yano wrote:
> >>> On Sat, 13 Feb 2021 20:39:39 +1000
> >>> Alvin Seville wrote:
> >>>> Windows build number: Win32NT 10.0.19042.0 Microsoft Windows NT 10.0.19042.0
> >>>> Windows Terminal version (if applicable): 1.5.10271.0
> >>>> Script to reproduce this issue:
> >>>> #!/usr/bin/env bashfunction outputText()
> >>>> {
> >>>>    local text=$1
> >>>>    local -i textLength=${#text}
> >>>>
> >>>>    local -i line="$(tput lines) / 2"
> >>>>    local -i col="$(tput cols) / 2 - $textLength / 2"
> >>>>
> >>>>    clear
> >>>>    echo -en "\e[$line;${col}H$text"
> >>>> }
> >>>> trap "outputText 'Hello world!'" SIGWINCH
> >>>> outputText 'Hello world!'while truedo
> >>>>      :done
> 
> >>> This is because cygwin console handles SIGWINCH when the input
> >>> messages is processed. If the process does not call either read()
> >>> or select(), SIGWINCH will not be sent. This is the long standing
> >>> problem of the implementation and hard to fix.
> 
> >> I came up with a solution for this issue and implemented that.
> >> It seems working as expected as far as I tested while I did not
> >> have to change the code much contrary to my concern.
> >>
> >> The point of the idea is to keep the basic structure of the
> >> console code unchanged and introduce a new thread which handle
> >> the only signals derived from input records. Handling of Ctrl-S
> >> and Ctrl-Q also added.
> >>
> >> I would like to submit the patch to cygwin-patches mailing list.
> >>
> >> Corinna, could you please have a look?
> 
> > v2: Problems when input echo is stopped by Ctrl-S is fixed.
> 
> Do these changes (still?) honour stty flags like isig, ixany, noflsh and handle 
> interrupt character settings for e.g.:
> 	intr = ^C; quit = ^\; swtch = ^Z; start = ^Q; stop = ^S; susp = ^Z;
> 	discard = ^O;
> ?

Basically yes. However, stty noflsh, flusho and Ctrl-O
does not take effect in the current code with/without
the patch.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>