How to get DISPLAY of emacsclient?

[Max Nikulin <manikulin@gmail.com>]

Hi,

Is it possible to get display of an emacsclient process? I mean either 
--display option argument or the DISPLAY environment variable namely for 
the client.

Unfortunately the value of following expression is the DISPLAY 
environment of the server process

     emacsclient --eval '(getenv "DISPLAY")'

I admit, it should work in most cases, but it is not robust:

     DISPLAY= emacs --daemon --display :0

causes empty string returned by `getenv'. In general, emacsclient's 
display is not necessary the same as the server's one. If I have got it 
correctly, the value is passed from client to server and there is a 
local "display" variable in server.el hidden from evaluated expression.

The context of the question is the following. Org-capture allows to 
create notes in non-distracting way (by setting :immediate-finish t 
property of the capture template). The idea is to save text currently 
selected in some application (either PRIMARY or CLIPBOARD) using a 
global window manager shortcut invoking

      emacsclient --eval '(org-capture nil "x")'

There is a pitfall. Emacs daemon has no frame at startup, so selection 
is inaccessible:

      emacsclient --eval "(org-get-x-clipboard 'PRIMARY)"

returns nil (it is merely a convenient way to call `gui-get-selection'). 
A workaround is to call `server-select-display', but to do so it is 
necessary to know display. That is why I am asking how to obtain display 
of emacsclient.