Re: org-x11idle-exists-p with emacs --daemon

[Max Nikulin <manikulin@gmail.com>]

Ihor, what I do not like in your patch is that an external process is 
unconditionally executed during load time. Earlier there was a (failed) 
attempt to limit it to X11.

- Unsure if Windows builds of Emacs may connect to X servers.
- MacOS does not use x11idle, it calls ioreg and perl instead.

In above cases, there might be a point to execute x11idle if a user is 
running remote Emacs session on a Windows or a MacOS machine (e.g. 
through ssh) from local X server. Unsure if somebody has ever tried it. 
The reason to try x11idle should be a test if current frame is 
associated with X.

A side note. I am aware that the following comment existed before your 
commit.
>   (and (eq 0 (call-process-shell-command
>               (format "command -v %s" org-clock-x11idle-program-name)))
>        ;; Check that x11idle can retrieve the idle time
>        ;; FIXME: Why "..-shell-command" rather than just `call-process'?
>        (eq 0 (call-process-shell-command org-clock-x11idle-program-name))))

`call-process' can not be used here because "command" is a shell 
built-in, not a real executable. I have another question. Why 
`locate-file' is not used instead?

     (locate-file command exec-path exec-suffixes 1))

https://emacs.stackexchange.com/questions/332/how-can-i-find-the-path-to-an-executable-with-emacs-lisp

On 30/10/2022 08:33, Ihor Radchenko wrote:
> Max Nikulin writes:
> 
>> In server.el I found
>>
>>       (frame-parameter frame 'display)
..
> 
> I do not understand.

echo "$DISPLAY"
:0
emacs -Q --daemon
emacsclient -nw

window-system
nil
(frame-parameter nil 'display)
":0"
(call-process "xterm")

So formally a tty frame has access to X11 server.

> Multiple X connection means non-deterministic idle time. Each individual
> X server will have its own idle time. The current approach with running
> `org-x11-idle-seconds' in current frame is the most reasonable in such
> scenario, IMHO.

I would say that minimal value should be used. However such case is 
rarely used and will be almost untested.

 From my point of view `org-clock-x11idle-program-name' approach is a 
bit fragile. I do not like "%s" substitutions while formatting shell 
commands. On the other hand it allows a complex command instead of 
executable, e.g.

dbus-send --print-reply --dest=org.gnome.Mutter.IdleMonitor 
/org/gnome/Mutter/IdleMonitor/Core org.gnome.Mutter.IdleMonitor.GetIdletime

for Wayland, see 
https://unix.stackexchange.com/questions/396911/how-can-i-tell-if-a-user-is-idle-in-wayland/492328
Perhaps, using Emacs D-BUS API would be even better.

x11idle as `org-clock-x11idle-program-name' default is questionable as 
well. Debian, Arch, Gentoo have xprintidle packages and this tool have 
some additional code.

My summary:
- To be really flexible (e.g. to support Wayland) 
`org-user-idle-seconds' should have an extension point allowing to 
specify elisp function.
- x11idle availability should be checked when X connection is detected, 
not at startup time and perhaps `locate-file' is better than "command" 
shell built-in.
- (frame-parameter nil 'display) might be more accurate in addition to 
`window-system' check.
- xprintidle should be either the default or an alternative during the test.
- I can not figure out how to detect --display argument of "emacs 
--daemon", but perhaps there is no point of time logging in the case of 
a headless process.
- There are tricky cases like remote Emacs or multihead Emacs. Custom 
idle function will allow to postpone their discussion till actual request.