bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Francesco Potortì]

I have Emacs running in a terminal under screen.  From there, I open a
frame under X.  So I have a text frame under screen and a graphical
frame under X.

When the graphical frame is open, if I try to suspend Emacs from the
terminal, I get the error in the subject, whose meaning is obscure.

When I close the X frame, Emacs can be suspended normally.

If the error is only issued in the case I just described, then it should
be rephrased, with something like "cannot suspend Emacs when a graphical
frame exists".

It would also be nice if the message explained how to close the
graphical frame from the text frame.  I tried
 (delete-frame (next-frame))
from the text frame but the only result was that the text frame became
unusable (not responding to commands any more).


In GNU Emacs 25.1.1 (x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2017-04-23, modified by Debian built on trouble
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:	Debian GNU/Linux 9.1 (stretch)

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Recent messages:
No following nondeleted message
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Wrote /home/pot/Mail/NOTIZIE [2 times]
Sunrise 6:08am (CEST), sunset 8:40pm (CEST) at Pisa (14:31 hrs daylight)
Preparing diary...done
Type "q" in help window to restore its previous buffer.
x-win-suspend-error: Cannot suspend Emacs while running under X [2 times]
Making completion list... [2 times]

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bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Eli Zaretskii]

> Date: Tue, 01 Aug 2017 11:01:18 +0200
> From: Francesco Potortì <Potorti@isti.cnr.it>
> 
> I have Emacs running in a terminal under screen.  From there, I open a
> frame under X.  So I have a text frame under screen and a graphical
> frame under X.
> 
> When the graphical frame is open, if I try to suspend Emacs from the
> terminal, I get the error in the subject, whose meaning is obscure.
> 
> When I close the X frame, Emacs can be suspended normally.
> 
> If the error is only issued in the case I just described, then it should
> be rephrased, with something like "cannot suspend Emacs when a graphical
> frame exists".

Done, thanks.

> It would also be nice if the message explained how to close the
> graphical frame from the text frame.  I tried
>  (delete-frame (next-frame))
> from the text frame but the only result was that the text frame became
> unusable (not responding to commands any more).

I encourage people to propose simple ways of doing that.

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Francesco Potortì]

>> It would also be nice if the message explained how to close the
>> graphical frame from the text frame.  I tried
>>  (delete-frame (next-frame))
>> from the text frame but the only result was that the text frame became
>> unusable (not responding to commands any more).
>
>I encourage people to propose simple ways of doing that.

Isn't the above behaviour a bug on its own?  The only way out I found
was to close Emacs from the graphical frame.

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Eli Zaretskii]

> Date: Sat, 05 Aug 2017 11:13:15 +0200
> From: Francesco Potortì <Potorti@isti.cnr.it>
> Cc: 27901-done@debbugs.gnu.org
> 
> >> It would also be nice if the message explained how to close the
> >> graphical frame from the text frame.  I tried
> >>  (delete-frame (next-frame))
> >> from the text frame but the only result was that the text frame became
> >> unusable (not responding to commands any more).
> >
> >I encourage people to propose simple ways of doing that.
> 
> Isn't the above behaviour a bug on its own?  The only way out I found
> was to close Emacs from the graphical frame.

It could be a bug, but if so, it's a separate bug.

And frankly, I don't understand what is the bug here: doing what you
did is not the usual way of deleting all frames but the current one.
I'd try "C-x 5 1" from the TTY frame first.

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Francesco Potortì]

>> Date: Sat, 05 Aug 2017 11:13:15 +0200
>> From: Francesco Potortì <Potorti@isti.cnr.it>
>> Cc: 27901-done@debbugs.gnu.org
>> 
>> >> It would also be nice if the message explained how to close the
>> >> graphical frame from the text frame.  I tried
>> >>  (delete-frame (next-frame))
>> >> from the text frame but the only result was that the text frame became
>> >> unusable (not responding to commands any more).
>> >
>> >I encourage people to propose simple ways of doing that.
>> 
>> Isn't the above behaviour a bug on its own?  The only way out I found
>> was to close Emacs from the graphical frame.
>
>It could be a bug, but if so, it's a separate bug.

Sure.  I did not yet file one because I'm not sure it is a bug.

>And frankly, I don't understand what is the bug here: doing what you
>did is not the usual way of deleting all frames but the current one.

I couldn't find a way.  But, apart from being usual, I think it is not
normal that a terminal frame becomes unusable as a consequence,
especially because I would not expect the behaviour to be undefined.

>I'd try "C-x 5 1" from the TTY frame first.

Tried.  But, as the docs say, that one deletes all other frames on the
same terminal, while I have a text and a graphical terminal.

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Eli Zaretskii]

> Date: Sat, 05 Aug 2017 13:44:48 +0200
> From: Francesco Potortì <Potorti@isti.cnr.it>
> Cc: 27901@debbugs.gnu.org
> 
> >I'd try "C-x 5 1" from the TTY frame first.
> 
> Tried.  But, as the docs say, that one deletes all other frames on the
> same terminal, while I have a text and a graphical terminal.

Then go to the GUI frame and type "C-x 5 0".

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Francesco Potortì]

>> Date: Sat, 05 Aug 2017 13:44:48 +0200
>> From: Francesco Potortì <Potorti@isti.cnr.it>
>> Cc: 27901@debbugs.gnu.org
>> 
>> >I'd try "C-x 5 1" from the TTY frame first.
>> 
>> Tried.  But, as the docs say, that one deletes all other frames on the
>> same terminal, while I have a text and a graphical terminal.
>
>Then go to the GUI frame and type "C-x 5 0".

The problem is that I have not access to the GUI (maybe this was not
clear from the beginning).

The terminal frame is running inside a terminal under Screen.  When I
access it remotely, I have no access to the GUI.  I cannot suspend Emacs
because there is a graphical frame alive, and I cannot close it because
I do not know how, and the only way I can think of makes the terminal
frame unusable (which I suspect is a bug).

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Eli Zaretskii]

> Date: Sat, 05 Aug 2017 19:39:35 +0200
> From: Francesco Potortì <Potorti@isti.cnr.it>
> Cc: 27901@debbugs.gnu.org
> 
> >Then go to the GUI frame and type "C-x 5 0".
> 
> The problem is that I have not access to the GUI (maybe this was not
> clear from the beginning).

It wasn't, not to me.

> The terminal frame is running inside a terminal under Screen.  When I
> access it remotely, I have no access to the GUI.  I cannot suspend Emacs
> because there is a graphical frame alive, and I cannot close it because
> I do not know how, and the only way I can think of makes the terminal
> frame unusable (which I suspect is a bug).

What does frame-list return?

And anyway, why do you insist on suspending Emacs?  Why not start a
shell instead?

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Francesco Potortì]

>> The terminal frame is running inside a terminal under Screen.  When I
>> access it remotely, I have no access to the GUI.  I cannot suspend Emacs
>> because there is a graphical frame alive, and I cannot close it because
>> I do not know how, and the only way I can think of makes the terminal
>> frame unusable (which I suspect is a bug).
>
>What does frame-list return?

(frame-list)
(#<frame emacs@tucano.isti.cnr.it 0x116995f8> #<frame F1 0xc41680>)

(next-frame)
#<frame F1 0xc41680>

(delete-frame (next-frame))
^^
shows the bug (I won't do it now because I am working remotely)

>And anyway, why do you insist on suspending Emacs?  Why not start a
>shell instead?

A shell inside Emacs does not have the environment I am looking for, so
the only way I am left with is to start a new terminal inside Screen.

But this is a workaround to a bug, not a solution.  So it appears to me
that I should indeed file a new bug report, right?

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Eli Zaretskii]

> Date: Sat, 05 Aug 2017 20:27:00 +0200
> From: Francesco Potortì <Potorti@isti.cnr.it>
> Cc: 27901@debbugs.gnu.org
> 
> >> The terminal frame is running inside a terminal under Screen.  When I
> >> access it remotely, I have no access to the GUI.  I cannot suspend Emacs
> >> because there is a graphical frame alive, and I cannot close it because
> >> I do not know how, and the only way I can think of makes the terminal
> >> frame unusable (which I suspect is a bug).
> >
> >What does frame-list return?
> 
> (frame-list)
> (#<frame emacs@tucano.isti.cnr.it 0x116995f8> #<frame F1 0xc41680>)
> 
> (next-frame)
> #<frame F1 0xc41680>
> 
> (delete-frame (next-frame))
> ^^
> shows the bug (I won't do it now because I am working remotely)

The F1 frame is a TTY frame, so it sounds like you are trying to
delete the frame through which you are communicating with Emacs?

And do you see the same problem when both frames are on the same
machine?

> A shell inside Emacs does not have the environment I am looking for

Why not?

> But this is a workaround to a bug, not a solution.  So it appears to me
> that I should indeed file a new bug report, right?

If so, please include a reproducible recipe.

Thanks.

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Eli Zaretskii]

> Date: Sat, 05 Aug 2017 21:43:31 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 27901@debbugs.gnu.org
> 
> > (frame-list)
> > (#<frame emacs@tucano.isti.cnr.it 0x116995f8> #<frame F1 0xc41680>)
> > 
> > (next-frame)
> > #<frame F1 0xc41680>
> > 
> > (delete-frame (next-frame))
> > ^^
> > shows the bug (I won't do it now because I am working remotely)
> 
> The F1 frame is a TTY frame, so it sounds like you are trying to
> delete the frame through which you are communicating with Emacs?

Yes, that's what happens here.  From the doc string of next-frame:

  (next-frame &optional FRAME MINIFRAME)

  Return the next frame in the frame list after FRAME.
  It considers only frames on the same terminal as FRAME.
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

So you shouldn't use next-frame for this, but instead find the frame
in the list that is other than the selected frame.

bug#27901: 25.1; x-win-suspend-error: Cannot suspend Emacs while running under X

[Francesco Potortì]

>> Date: Sat, 05 Aug 2017 20:27:00 +0200
>> From: Francesco Potortì <Potorti@isti.cnr.it>
>> Cc: 27901@debbugs.gnu.org
>> 
>> >> The terminal frame is running inside a terminal under Screen.  When I
>> >> access it remotely, I have no access to the GUI.  I cannot suspend Emacs
>> >> because there is a graphical frame alive, and I cannot close it because
>> >> I do not know how, and the only way I can think of makes the terminal
>> >> frame unusable (which I suspect is a bug).
>> >
>> >What does frame-list return?
>> 
>> (frame-list)
>> (#<frame emacs@tucano.isti.cnr.it 0x116995f8> #<frame F1 0xc41680>)
>> 
>> (next-frame)
>> #<frame F1 0xc41680>
>> 
>> (delete-frame (next-frame))
>> ^^
>> shows the bug (I won't do it now because I am working remotely)
>
>The F1 frame is a TTY frame, so it sounds like you are trying to
>delete the frame through which you are communicating with Emacs?

Wow, that's it, thanks!  I had not realised that (next-frame) is the
wrong way to choose a frame, because it looks for frames in the same
terminal!

I was looking for a function that gives me the same frame that C-x 5 o
switches to.

>And do you see the same problem when both frames are on the same
>machine?

Yes, I only tried those things when on the same machine, but now the
reason looks obvious to me: I was just deleting the frame I was using,
because (next-frame) returns that, so there is no bug here.

>> A shell inside Emacs does not have the environment I am looking for
>
>Why not?

Because I want a real terminal, not a shell buffer, and I do not want to
use a terminal emulator inside Emacs.  But this is out of scope.

Ok, so now the problem reduces to:
- find a simple recipe for deleting all GUI frames from a terminal frame
- add this recipe to the error message mentioned at the start of this
  bug report

Thanks so far