FTFL.CA/blog

Emacs as an X Clipboard Manager

This post is now deprecated. See Emacs as an X Clipboard Manager post, take 2.

Until recently, I was using clipit, a fork of parcellite, as an X clipboard manager. Discovering a bug in Emacs that presented when a clipboard manager was running prompted me to look for an alternative to clipit. I was pleased to discover the clipmon package, which worked relatively well, but it also has a showstopping bug. Moreover, it seems the only way to monitor the X clipboard from within Emacs is to poll it. I'm not keen on something inside Emacs having to wake up every second or two to check the X clipboard. An alternative is to move the polling outside of Emacs with this shell script.

Polling solution (I am not using this)

#!/bin/sh

occ=$(xclip -sel clip -o | sed 's/[\"]/\\&/g')

while sleep 2; do
    ncc=$(xclip -sel clip -o | sed 's/[\"]/\\&/g')
    if [ "${occ}" != "${ncc}" ]; then
        emacsclient -e "(kill-new \"${ncc}\")"
        occ=${ncc}
    fi
done

This is a simple solution and it works, but it still bothers me that I'm polling the clipboard. An event driven solution would be better. My Emacs experience drives me to try and write an on-clipboard-change hook for X, but that's beyond the scope of my mini holiday project.

With few exceptions, I only use two applications outside of Emacs (a web browser and a terminal emulator) and both are customizable. Each time I copy something to the X clipboard in those applications, I could also add the new clipboard entry to the Emacs kill ring. Here are the customizations I add to the init file of my primary browser, Conkeror.

Event-driven solution (Conkeror modifications)

function ekr (cc) {
    if (typeof cc === 'undefined') { cc = read_from_clipboard(); }
    cc = cc.replace(/([^\\]*)\\([^\\]*)/g, "$1\\\\$2");
    cc = cc.replace(/"/g, '\\"');
    cc = cc.replace(/'/g, "'\\''");
    var ecc = "emacsclient -e '(kill-new \"" + cc + "\")' > /dev/null";
    shell_command_blind(ecc);
}

interactive(
    "ekr_cmd_copy",
    "Copy the selection to the clipboard and the Emacs kill ring",
    function (I) {
        call_builtin_command(I.window, "cmd_copy", true);
        ekr();
    }
);

undefine_key(caret_keymap,"M-w");
define_key(caret_keymap,"M-w", "ekr_cmd_copy");
undefine_key(content_buffer_normal_keymap,"M-w");
define_key(content_buffer_normal_keymap,"M-w", "ekr_cmd_copy");
undefine_key(special_buffer_keymap,"M-w");
define_key(special_buffer_keymap,"M-w", "ekr_cmd_copy");
undefine_key(text_keymap,"M-w");
define_key(text_keymap,"M-w", "ekr_cmd_copy");

I also add calls to ekr(); at the end of the kill-region and kill-ring-save commands in modules/commands.js, the cut-to-end-of-line command in modules/content-buffer-input.js and a call to ekr(text); at the end of the copy_text function in modules/elements.js.

Event-driven solution (Tmux customizations)

When eshell doesn't cut it, the second place I find myself outside of Emacs is in urxvt/tmux. To accomplish the same thing there, I added the line below to ~/.tmux.conf.

bind-key -temacs-copy M-w copy-pipe 'c2e -r'

Here is the c2e script.

#!/bin/sh

# c2e: Copy text to the Emacs kill ring.
#
# With no arguments, send the contents of the X clipboard to the Emacs kill ring.
# With -r, first set the clipboard to the contents read from standard input.
# With -s, instead send X primary selection to the Emacs kill ring.

if [ "${1}" = '-r' ]; then
    exec xclip -sel clip -i -f | \
        emacsclient -e "(kill-new \"$(sed 's/[\"]/\\&/g')\")"
elif [ "${1}" = '-s' ]; then
    exec xclip -o | \
        emacsclient -e "(kill-new \"$(sed 's/[\"]/\\&/g')\")"
else
    exec xclip -sel clip -o | \
        emacsclient -e "(kill-new \"$(sed 's/[\"]/\\&/g')\")"
fi

Window manager (StumpWM) customizations to interact with the clipboard manager (Emacs kill ring)

To make the new clipboard manager (the Emacs kill ring) easily accessible, I created a simple command and keybinding for my window manager, StumpWM.

(defcommand eaacm () ()
  "Emacs as a clipboard manager."
  (run-or-raise "emacsclient -nc" '(:class "Emacs"))
  (run-shell-command "emacsclient -n -e \
    '(save-window-excursion (delete-other-windows) (counsel-yank-pop))'"))

That function is based on the assumption you have counsel installed. If you prefer helm, try something like this.

(defcommand eaacm () ()
  "Emacs as a clipboard manager."
  (run-or-raise "emacsclient -nc" '(:class "Emacs"))
  (run-shell-command "emacsclient -n -e '(let ((helm-full-frame t)) \
    (save-window-excursion (delete-other-windows) (helm-show-kill-ring)))'"))

You will want to define a keybinding that works for you.

(define-key *root-map* (kbd "c") "eaacm")

Now, no matter what application is focused, I hit C-t c and I'm shown a nice interface to the kill ring. Both Counsel and Helm even include actions, bound by default to M-o t and C-c C-k, to move an entry to the top of the kill ring and to the X clipboard.

I also created two simple StumpWM commands and keybindings to call the c2e script for the rare occasions when I am copying text in some other application.

(defcommand c2e () ()
  "Copy the X clipboard contents to the Emacs kill ring."
  (run-shell-command "c2e"))

(defcommand s2e () ()
  "Copy the X selection contents to the Emacs kill ring."
  (run-shell-command "c2e -s"))

(define-key *root-map* (kbd "C")        "c2e")
(define-key *root-map* (kbd "s")        "s2e")

It's only been a few days, but so far Emacs makes a nice X clipboard manager.

Last updated 2021-05-10 17:18 UTC. Added a deprecation note. Some of the comments reference older versions of the text.