✨ emacs-everywhere-linux-copy-function emacs-everywhere-paste-cmd

defcustom for alternative methods of handling the clipboard on linux
also added documentation of the added as well as other customizations

Overlaps with issue tecosaur#28 and maybe also a fix for issue tecosaur#10

The modifications have at least a few weak spots.
  1. emacs-everywhere-paste-cmd should maybe be a function
  2. organization of added functions and vars
  3. (eval `(... ,@Args)) is (apply ...) elsewhere

1. There's a solid argument that it's easier to use as a list:
the intent is clearer and there is little ceremony.
but it is weaker (can't drop into elisp) and inconsistent with
emacs-everywhere-filename-function and emacs-everywhere-linux-copy-function

2. I get the sense things were well organized before I started poking around.
But I'm not deep enough into to understand what should go where.

3. `emacs-everywhere-call` uses
    (apply #'call-process command nil t nil (remq nil args))
  Just saw that. That looks cleaner than using eval. I'm here to
  practice lisp. Got carried away in emacs-everywhere-paste-cmd?

README.org

@@ -51,4 +51,26 @@ C-k= still copies the content to the clipboard, but never pastes.
 -----
 
 ^{*†*} This requires the Emacs daemon to be running, but that's super easy.
-Just call =emacs --daemon= and you're sorted!
+Just call =emacs --daemon= or =M-x server-start= and you're sorted!
+
+* Customize
+
+** Example hook
+   The default simulated key chord pastes into Pidgin as a single line. To preserve newlines, the desired combo is =Control+V= (instead of the default =Shift+Insert=). Here we create a function that temporarily modifies the paste command when emacs-everywhere was launched with Pidgin focused.
+   #+begin_src elisp
+   ;; "Paste as plaintext" using "Control Shift V" for GTK app Pidgin IM
+   (defun emacs-everywhere-pidgin-paste ()
+     (when (eq (emacs-everywhere-app-class emacs-everywhere-current-app) "Pidgin")
+       (set (make-local-variable 'emacs-everywhere-paste-cmd)
+            '("xdotool" "key" "--clearmodifiers" "Control+V"))))
+
+  (add-hook 'emacs-everywhere-init-hooks 'emacs-everywhere-pidgin-paste)
+   #+end_src
+
+** Highlights
+
+Window and app names that will open in markdown mode are enumerated in =emacs-everywhere-markdown-windows= and =emacs-everywhere-markdown-apps=.
+
+How the clipboard is handled can be redefined using =emacs-everywhere-linux-copy-function= and  =emacs-everywhere-paste-cmd=.
+
+See =M-x customize-groups [RET] emacs-everywhere= for the full list. Or peak at the source.

emacs-everywhere.el

@@ -34,8 +34,15 @@
   :type 'boolean
   :group 'emacs-everywhere)
 
+(defcustom emacs-everywhere-paste-cmd nil
+  "How to paste back. List like (cmd arg1 arg2). Used with `emacs-everywhere-paste'.
+Example: '(\"xdotool\" \"key\" \"--clearmodifiers\" \"Shift+Insert\")
+Consider pairing with `make-local-variable' in `emacs-everywhere-init-hooks'"
+  :type 'sexp
+  :group 'emacs-everywhere)
+
 (defcustom emacs-everywhere-markdown-windows
-  '("Stack Exchange" "Stack Overflow" "Reddit" ; Sites
+  '("Stack Exchange" "Stack Overflow" "Reddit"     ; Sites
     "Pull Request" "Issue" "Comparing .*\\.\\.\\." ; Github
     "Discord")
   "For use with `emacs-everywhere-markdown-p'.
@@ -224,6 +231,45 @@ buffers.")
       (org-ctrl-c-ctrl-c)
     (emacs-everywhere-finish)))
 
+(defun emacs-everywhere-what-paste-cmd ()
+  "What command to use to paste."
+  (cond (emacs-everywhere-paste-cmd
+         emacs-everywhere-paste-cmd)
+        ((eq system-type 'darwin)
+         '("osascript"
+           "-e"
+           "tell application \"System Events\" to keystroke \"v\" using command down"))
+        (t
+         '("xdotool"
+           "key"
+           "--clearmodifiers"
+           "Shift+Insert"))))
+
+(defun emacs-everywhere-paste ()
+  "Paste with operating system specific program or custom cmd"
+  (interactive)
+  (let* ((cmd-list (emacs-everywhere-what-paste-cmd))
+         (cmd (car cmd-list))
+         (args (cdr cmd-list)))
+    (eval `(call-process ,cmd nil nil nil ,@args))))
+
+(defun emacs-everywhere-linux-copy ()
+  "Put the current buffer onto the clipboard."
+  (let ((inhibit-message t)
+        (require-final-newline nil)
+        write-file-functions)
+    (write-file buffer-file-name)
+    (pp (buffer-string))
+    (call-process "xclip" nil nil nil "-selection" "clipboard" buffer-file-name)))
+
+(defcustom emacs-everywhere-linux-copy-function
+  #'emacs-everywhere-linux-copy
+  "A function to populate the clipboard. To be pasted into original app by `emacs-everywhere-paste'"
+  :type 'function
+  :group 'emacs-everywhere)
+
+
+
 (defun emacs-everywhere-finish (&optional abort)
   "Copy buffer content, close emacs-everywhere window, and maybe paste.
 Must only be called within a emacs-everywhere buffer.
@@ -236,12 +282,7 @@ Never paste content when ABORT is non-nil."
       (run-hooks 'emacs-everywhere-final-hooks)
       (gui-select-text (buffer-string))
       (unless (eq system-type 'darwin) ; handle clipboard finicklyness
-        (let ((inhibit-message t)
-              (require-final-newline nil)
-              write-file-functions)
-          (write-file buffer-file-name)
-          (pp (buffer-string))
-          (call-process "xclip" nil nil nil "-selection" "clipboard" buffer-file-name))))
+        (funcall emacs-everywhere-linux-copy-function)))
     (sleep-for 0.01) ; prevents weird multi-second pause, lets clipboard info propagate
     (let ((window-id (emacs-everywhere-app-id emacs-everywhere-current-app)))
       (if (eq system-type 'darwin)
@@ -255,11 +296,7 @@ Never paste content when ABORT is non-nil."
       (when (and (frame-parameter nil 'emacs-everywhere-app)
                  emacs-everywhere-paste-p
                  (not abort))
-        (if (eq system-type 'darwin)
-            (call-process "osascript" nil nil nil
-                          "-e" "tell application \"System Events\" to keystroke \"v\" using command down")
-          (call-process "xdotool" nil nil nil
-                        "key" "--clearmodifiers" "Shift+Insert"))))
+        (emacs-everywhere-paste)))
     ;; Clean up after ourselves in case the buffer survives `server-buffer-done'
     ;; (b/c `server-existing-buffer' is non-nil).
     (emacs-everywhere-mode -1)