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
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