System shutdown messages

System shutdown messages

[Ken Brown]

A Cygwin emacs user has asked 
(http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23483) whether emacs can 
auto-save files when he shuts down Windows from the Start Menu.  Is 
there a way for a Cygwin process to listen for Windows system shutdown 
messages?

Ken

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: System shutdown messages

[Jon Turney]

On 09/05/2016 14:35, Ken Brown wrote:
> A Cygwin emacs user has asked
> (http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23483) whether emacs can
> auto-save files when he shuts down Windows from the Start Menu.  Is
> there a way for a Cygwin process to listen for Windows system shutdown
> messages?

This seems entirely possible using the Win32 API.

For emacs-w32, it's probably straightforward to handle WM_ENDSESSION in 
the message loop similarly to WM_CLOSE

(Note that the process will be terminated if you return from processing 
a WM_ENDSESSION message)

For emacs-nox and emacs-x11 it's more complex, as you'd have to create 
your own hidden window to receive the WM_ENDSESSION, and either select() 
on a /dev/windows fd or block in GetMessage() on a separate thread.

(see [1] for an example of the latter approach as used in the X server)

But I'm not sure that's the best approach, or if wouldn't be more 
appropriate to arrange for SIGTERM to be sent to emacs (or whatever) by 
mintty or the X server when an WM_ENDSESSION is received...

[1] https://cgit.freedesktop.org/xorg/xserver/tree/hw/xwin/winmsgwindow.c

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: System shutdown messages

[Ken Brown]

On 5/9/2016 1:20 PM, Jon Turney wrote:
> On 09/05/2016 14:35, Ken Brown wrote:
>> A Cygwin emacs user has asked
>> (http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23483) whether emacs can
>> auto-save files when he shuts down Windows from the Start Menu.  Is
>> there a way for a Cygwin process to listen for Windows system shutdown
>> messages?
>
> This seems entirely possible using the Win32 API.
>
> For emacs-w32, it's probably straightforward to handle WM_ENDSESSION in
> the message loop similarly to WM_CLOSE
>
> (Note that the process will be terminated if you return from processing
> a WM_ENDSESSION message)
>
> For emacs-nox and emacs-x11 it's more complex, as you'd have to create
> your own hidden window to receive the WM_ENDSESSION, and either select()
> on a /dev/windows fd or block in GetMessage() on a separate thread.
>
> (see [1] for an example of the latter approach as used in the X server)
>
> But I'm not sure that's the best approach, or if wouldn't be more
> appropriate to arrange for SIGTERM to be sent to emacs (or whatever) by
> mintty or the X server when an WM_ENDSESSION is received...

Thanks, Jon.  Yes, the latter approach seems much better.  Of course, SHTDI.

Ken


--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

Re: System shutdown messages

[Ken Brown]

On 5/9/2016 1:20 PM, Jon Turney wrote:
> On 09/05/2016 14:35, Ken Brown wrote:
>> A Cygwin emacs user has asked
>> (http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23483) whether emacs can
>> auto-save files when he shuts down Windows from the Start Menu.  Is
>> there a way for a Cygwin process to listen for Windows system shutdown
>> messages?
>
> This seems entirely possible using the Win32 API.
>
> For emacs-w32, it's probably straightforward to handle WM_ENDSESSION in
> the message loop similarly to WM_CLOSE

This was indeed straightforward, so I went ahead and did it.  But I 
didn't try to do anything for emacs-X11 and emacs-nox because it's more 
complicated, and...

> But I'm not sure that's the best approach, or if wouldn't be more
> appropriate to arrange for SIGTERM to be sent to emacs (or whatever) by
> mintty or the X server when an WM_ENDSESSION is received...

... I hope Someone will do this.

Ken

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple