Re: Can Emacs started with `-nw' option view pdf with pdf-tools?

[Felix Dietrich]

Thibaut Verron <thibaut.verron@gmail.com> writes:

> Le sam. 17 juil. 2021 à 12:38, Hongyi Zhao <hongyi.zhao@gmail.com> a écrit :
>>
>> On Sat, Jul 17, 2021 at 3:00 PM Arthur Miller <arthur.miller@live.com> wrote:
>> >
>> > Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>> >
>> > > I'm using auctex and pdf-tools with Emacs,  and find that if I start
>> > > Emacs with `emacs -nw`, the pdf-tools won't let me preview pdf.
>> > >
>> > > Any hints?
>> > >
>> > > Regards
>> >
>> > Yes you need a GUI window to display images (which is what pdf-tools
>> > does).
>>
>> Basically, if I start emacs without `-nw' option, the `C-c C-v' will
>> do the job described here automatically. But how to let `C-c C-v' open
>> a GUI window for this case?
>
> Emacs with -nw has no concept of "GUI window", so I don't think that
> it is possible.

Emacs can handle (info "(elisp) Multiple Terminals") and can display
text terminal and graphical terminal frames at the same time.

> If you use emacs as a daemon and start a terminal client with
> emacsclient -t, there might be a way to have C-c C-v open a gui client
> with pdf-view, but that would be tricky.

For the X Display Server, use (make-frame-on-display (getenv "DISPLAY"))
to create a graphical frame.  If Emacs was started with the “-nw”
options, this will run the necessary initialisation steps (according to
the manual).  The environment variable “DISPLAY” should already be set
in your terminal emulator and, therefore, in the Emacs instance you
started in the terminal emulator.  For single user systems its value is
commonly “:0”.

When running Emacs remotely via ssh, you may allow remote X client
applications to create their windows on your local desktop by passing
the “-X” option (or setting “ForwardX11” in your “~/.ssh/config”).  This
will create a tunnel for X11 applications from the remote system to your
local X Server and set the “DISPLAY” variable accordingly.  Performance
may be lagging, though.

Here is a sketch for a function that creates a graphical terminal frame
before it calls the command that “C-c C-v” runs.  You need to fill in
the command.  You can find it with “C-h c C-c C-v”.  Beware: the code is
untested.


    (defun view-pdf-in-graphical-frame ()
      (interactive)
      (unless window-system
        ;; Create a graphical frame first.
        (let ((display (getenv "DISPLAY")))
          (when (seq-empty-p display)
            (user-error "No DISPLAY environment variable set"))
          (select-frame (make-frame-on-display display))))
      ;; Replace ‘C-c_C-v_command’ with the actual name of the command.
      (call-interactively 'C-c_C-v_command))
    

-- 
Felix Dietrich