Subject: bug#51374: New options for emacsclient

From: Gregory Heytings <[email-masked]>
Date: Sun, 24 Oct 2021 14:27:42 +0000

When emacsclient is used in a terminal, emacsclient FILE opens a 
non-graphical Emacs frame, and emacsclient -c FILE always creates a new 
graphical Emacs frame.  A third option, which creates a graphical frame if 
none exist and reuses a graphical frame is one exists, would be useful 
(see for example [1] and [2]).

Patch attached.

[1] https://superuser.com/questions/358037/emacsclient-create-a-frame-if-a-frame-does-not-exist 
[2] https://emacs.stackexchange.com/questions/12894/make-emacsclient-create-a-frame-only-if-there-isnt-one-already

From f44c01bb1f1a90aa511186e5310fecda1d107985 Mon Sep 17 00:00:00 2001
From: Gregory Heytings <[email-masked]>
Date: Sun, 24 Oct 2021 14:14:32 +0000
Subject: [PATCH] New emacsclient option to either create or reuse an existing
 frame.

* lib-src/emacsclient.c (reuse_frame): New variable.
(longopts): New option.
(decode_options): Decode the new option.
(print_help_and_exit): Document the new option.
(main): Use the new option.

* doc/emacs/misc.texi (emacsclient Options): Document the new option.
---
 doc/emacs/misc.texi   |  5 +++++
 lib-src/emacsclient.c | 13 ++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/doc/emacs/misc.texi b/doc/emacs/misc.texi
index 5123a716dc..810d212021 100644
--- a/doc/emacs/misc.texi
+++ b/doc/emacs/misc.texi
@@ -1986,6 +1986,11 @@ emacsclient Options
 can customize this behavior with the variable @code{initial-buffer-choice}
 (@pxref{Entering Emacs}).
 
+@item -r
+@itemx --reuse-frame
+Create a new graphical @dfn{client frame} if none exists, otherwise
+use an existing Emacs frame.
+
 @item -F @var{alist}
 @itemx --frame-parameters=@var{alist}
 Set the parameters for a newly-created graphical frame
diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index cff3cec2a7..0e800dd7e8 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -116,6 +116,9 @@ Copyright (C) 1986-1987, 1994, 1999-2021 Free Software Foundation, Inc.
 /* True means open a new frame.  --create-frame etc.  */
 static bool create_frame;
 
+/* True means reuse a frame if it already exists.  */
+static bool reuse_frame;
+
 /* The display on which Emacs should work.  --display.  */
 static char const *display;
 
@@ -165,6 +168,7 @@ Copyright (C) 1986-1987, 1994, 1999-2021 Free Software Foundation, Inc.
   { "tty",	no_argument,       NULL, 't' },
   { "nw",	no_argument,       NULL, 't' },
   { "create-frame", no_argument,   NULL, 'c' },
+  { "reuse-frame", no_argument,   NULL, 'r' },
   { "alternate-editor", required_argument, NULL, 'a' },
   { "frame-parameters", required_argument, NULL, 'F' },
 #ifdef SOCKETS_IN_FILE_SYSTEM
@@ -551,6 +555,11 @@ decode_options (int argc, char **argv)
 	  create_frame = true;
           break;
 
+	case 'r':
+	  create_frame = true;
+	  reuse_frame = true;
+	  break;
+
 	case 'p':
 	  parent_id = optarg;
 	  create_frame = true;
@@ -647,6 +656,8 @@ print_help_and_exit (void)
 -nw, -t, --tty 		Open a new Emacs frame on the current terminal\n\
 -c, --create-frame    	Create a new frame instead of trying to\n\
 			use the current Emacs frame\n\
+-r, --reuse-frame	Create a new frame if none exists, otherwise\n\
+			use the current Emacs frame\n\
 ", "\
 -F ALIST, --frame-parameters=ALIST\n\
 			Set the parameters of a new frame\n\
@@ -1941,7 +1952,7 @@ main (int argc, char **argv)
   if (nowait)
     send_to_emacs (emacs_socket, "-nowait ");
 
-  if (!create_frame)
+  if (!create_frame || reuse_frame)
     send_to_emacs (emacs_socket, "-current-frame ");
 
   if (display)
-- 
2.33.0