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Date: Wed, 15 Apr 2009 16:14:13 +0100
Message-ID: <416096c60904150814y45976747qa7878d1ed256fc9@mail.gmail.com>
Subject: Re: popup consoles on Windows 7
From: Andy Koppe <andy DOT koppe AT gmail DOT com>
To: cygwin AT cygwin DOT com
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I think I found the reason why consoles pop up for mintty and XWin on
Windows 7. Cygwin's fhandler_console.cc uses a clever trick where it
allocates a console on an invisible custom "window station". I tried
to do the same in the mintty child process, but found that
AllocConsole() no longer cares whether a custom window station has
been selected with SetProcessWindowStation(): the console window is
opened on the default window station anyway.

Here's what I did, between forkpty() and exec():

    DWORD version = GetVersion();
    version = ((version & 0xff) << 8) | ((version >> 8) & 0xff);
    if (version >= 0x0601) {
      HWINSTA wst0 = GetProcessWindowStation();
      HWINSTA wst = CreateWindowStation (NULL, 1, WINSTA_ALL_ACCESS, &sa);
      SetProcessWindowStation(wst);
      AllocConsole();
      SetProcessWindowStation(wst0);
      CloseWindowStation(wst);
    }

Debug output showed that the function calls all succeeded, and that
CreateWindowStation() did create a station separate from the default
one.

No idea what to do about it ...

Andy


2009/4/5 Andy Koppe:
> MinTTY is a -mwindows app, which so far seemed to work well on XP and
> Vista, because no console is popped up, not even momentarily. Not so
> on Windows 7, unfortunately. forkpty() and execve() are used to create
> the child process and invoke the command, whereby it appears to be the
> exec call that causes a console to pop up.
>
> I guess the fact that rxvt is a CUI app explains why its trick for
> creating a hidden console didn't work in MinTTY: rxvt opens that
> console in the main process, which in a GUI app isn't passed down to a
> child process.
>
> So here's what I've done instead in 0.4-beta1: call AttachConsole(-1)
> to attach to any parent console from the main mintty process, and call
> it again from the child process to pass it down to that. If there is
> no console, create one using AllocConsole (in the child process), and
> hide it using ShowWindowAsync.
>
> Unfortunately two problems have been reported with this. The console
> isn't always hidden, and a really weird one on a 64-bit Windows 7:
> when invoking mintty from a bash running in a console, that console
> window locks up. I'm rather stuck on what to do about those, so
> suggestions would be welcome.
>
> Also, a couple of questions.
>
> When mintty is invoked from a shortcut or the Run dialog, the main
> process actually does get a console, i.e. GetConsoleWindow() returns a
> handle, but it doesn't appear on the screen, and the child process
> can't attach to it using AttachConsole(). When invoked from a console
> or rxvt, GetConsoleWindow() returns null. What's the reason for that?
>
> Furthermore, I'd previously seen the popup console problem on an old
> Cygwin install on XP, but updating cured it. So has this been
> addressed in the Cygwin DLL in the past, and is it likely that it can
> be solved for Windows 7 too? Any idea what might have changed in
> Windows that causes this issue?
>
> Btw, XWin is affected by this too. Starting it from a shortcut on
> Vista is fine, but on 7 multiple consoles pop up briefly, and one
> stays up.
>
> Andy
>

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