[PATCH] Cygwin: pty: Disable pseudo console if TERM is dumb or not set.

Takashi Yano takashi.yano@nifty.ne.jp
Thu Aug 27 04:07:20 GMT 2020

On Wed, 26 Aug 2020 19:36:06 +0200
Corinna Vinschen wrote:
> On Aug 26 21:00, Takashi Yano via Cygwin-patches wrote:
> > Pseudo console generates escape sequences on execution of non-cygwin
> > apps.  If the terminal does not support escape sequence, output will
> > be garbled. This patch prevents garbled output in dumb terminal by
> > disabling pseudo console.
> I'm a bit puzzled by this patch.  We had code handling emacs and dumb
> terminals explicitely in the early forms of the first incarnation of
> the pseudo tty code, but fortunately you found a way to handle this
> without hardcoding terminal types into Cygwin.  Why do you think we
> have to do this now?

What previously disccussed was the problem that the clearing
screen at pty startup displays garbage (^[[H^[[2J) in emacs.
Finally, this was settled by eliminating clear-screen and
triggering redraw-screen instead at the first execution of
non-cygwin app.

However, the problem reported in
still remains. 

What's worse in the new implementation, pseudo console sends
ESC[6n (querying cursor position) internally on startup and
waits for a response. This causes hang if pseudo console is
started in dumb terminal.

This patch is for fixing this issue.

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

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