Re: winpty injection

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Apr  6 21:22, Johannes Schindelin wrote:
> Hi Thomas,
> 
> On Fri, 6 Apr 2018, Thomas Wolff wrote:
> 
> > Am 06.04.2018 um 12:31 schrieb Johannes Schindelin:
> > >
> > > On Fri, 6 Apr 2018, Thomas Wolff wrote:
> > >
> > > > These symptoms suggest to me: winpty is not the culprit, but its
> > > > presence in the invocation chain seems to trigger the effect in a
> > > > yet unclear way.
> > >
> > > Sure, `winpty` is not the culprit.
> > >
> > Actually, as it turns out, winpty *is* the culprit. I've raised winpty
> > issue https://github.com/rprichard/winpty/issues/140 about it.
> 
> I am not sure you understand the issue here. The `winpty` helper opens a
> Win32 console for the native Windows application to use. Then it polls
> this (hidden) console for changes and tries to reflect them in the Cygwin
> pty.
> 
> If that Windows application writes something to that console containing
> Escape sequences, then those Escape sequences occupy certain cells in that
> matrix of rows and columns making up that console.
> 
> However, if the Windows application uses random-access functions to put
> individual characters into cells specified by given absolute positions,
> winpty cannot tell the difference. So what winpty would be asked to
> consider an ANSI sequence may never have been an ANSI sequence.
> 
> Sure, this is a construed example, but it shows that you should not be so
> sure that winpty *can* detect ANSI sequences and handle them in a way that
> *you* want.
> [...]
> In the least, therefore, it should be configurable. And I would even argue
> that the default behavior should remain the same as current in Cygwin: do
> not use winpty by default.
> 
> Of course, this is just my opinion, and I am but a user and infrequent
> contributor to Cygwin. But I would hope that the Cygwin maintainers use a
> lot of care and reluctant deliberation when considering a potentially
> disruptive change such as this, a change that may very well occupy a lot
> of time in dealing with the unwanted fallout.

Point taken.  Nicely explained.

However, that makes calling winpty from Cygwin a somewhat questionable
endeavor.  Adding optional code paths which are in all likelyhood not
used very often, thus not tested very often, thus bound to rot, are not
really something I'm looking forward to.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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