Re: Getting X selection reliably (Re: idea for capture anywhere in x)

[Max Nikulin]

On 14/11/2022 09:06, Ihor Radchenko wrote:
> Max Nikulin writes:
>
> > Depending of particular capture template (even with :immediate-finish t)
> > empty selection may or may not be an error. In Samuel's case it is an
> > error. Unfortunately, while the template is processed, signaled errors
> > are caught and their text is inserted into the text. That is why in my
> > example I put checks outside of `org-capture'.
>
> Are you sure? `org-get-x-clipboard' returns nil in case of error and
> `org-capture-fill-template' assigns empty string to v-x when no
> clipboard value can be obtained.

I did not mean elisp error. It is a trouble from the point of view of a 
user. Their expect to get selection text, but actually useless empty 
string is inserted. However capturing stale selection (from previous 
action) is an equally annoying trouble. That is why I believe, the only 
reliable way is to present result of capture to the user, so if 
something goes wrong then they may redo selection and capture. Samuel 
may weight distracting popup vs. a chance of useless capture differently.

> > We may:
> > - Add a capture template option that allows errors to pass through to
> > the caller. Then a user may add %(...) expression with all necessary checks.
>
> I am not very sure what kind of errors you are talking about. AFAIU, we
> are talking about scenarios when user explicitly wants one of
> PRIMARY/CLIPBOARD/SECONDARY, don't we?

I mean a way to propagate an error signaled during capture expansion to 
the caller of emacsclient, so user may be notified about the issue 
instead of silently getting "[ERROR ...]" in the captured heading.

> > I have no idea how to get "emacs -display" argument and I need to look
> > into emacsclient source and server.el to figure out which way client's
> > display argument is passed to the server process.
>
> Maybe it can be considered an Emacs bug or something to improve on Emacs
> side?

See Max Nikulin to emacs-devel. How to get DISPLAY of emacsclient? Fri, 
25 Nov 2022 22:17:54 +0700. mid:tlqmb3$ic$1@ciao.gmane.io

A workaround is

  emacsclient --display "$DISPLAY" --eval ...

Unlike for most of X applications, --display option of emacsclient not 
only overrides the value of the DISPLAY environment, in addition it 
causes creation of a hidden frame, so `org-get-x-clipboard' is able to 
get selection text. I am unsure concerning behavior in other OSes. At 
least special values display are used internally, users are unlikely 
familiar with the concept of display. Unfortunately I can not check 
precise behavior for macOS or Windows. I would not mind to have an 
option like --force-display that does not require fetching the value 
from environment (to avoid explicit shell wrapper in .desktop files) or 
special values on non-X systems.

Likely the "--display" hack should be mentioned in the manual and in the 
templates docscring.