From 2bcc2160c9f7f16c5e9cd815b8074de27f30896d Mon Sep 17 00:00:00 2001
From: Gregory Heytings <gregory@heytings.org>
Date: Fri, 5 Nov 2021 00:14:30 +0100
Subject: [PATCH] New emacsclient option to either create or reuse an existing
 frame.

* doc/emacs/misc.texi (emacsclient Options): Document the new option.

* doc/man/emacsclient.1: Mention the new option (bug#51374).
* etc/NEWS: Mention the new option.

* 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   |  5 +++++
 doc/man/emacsclient.1 |  3 +++
 etc/NEWS              |  8 ++++++++
 lib-src/emacsclient.c | 13 ++++++++++++-
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/doc/emacs/misc.texi b/doc/emacs/misc.texi
index f66b69cdd73..4be47990d1f 100644
--- a/doc/emacs/misc.texi
+++ b/doc/emacs/misc.texi
@@ -1992,6 +1992,11 @@ the new frame displays the @file{*scratch*} buffer by default.  You
 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/doc/man/emacsclient.1 b/doc/man/emacsclient.1
index ba64efa282c..cc58f106e69 100644
--- a/doc/man/emacsclient.1
+++ b/doc/man/emacsclient.1
@@ -69,6 +69,9 @@ start Emacs in daemon mode, and try to connect to it.
 .B -c, \-\-create-frame
 Create a new frame instead of trying to use the current Emacs frame.
 .TP
+.B -r \-\-reuse-frame
+Reuse an existing frame if one exists, otherwise create a new frame.
+.TP
 .B \-F, \-\-frame-parameters=ALIST
 Set the parameters of a newly-created frame.
 .TP
diff --git a/etc/NEWS b/etc/NEWS
index 1b3f4c0524f..899f3567e6e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -102,6 +102,14 @@ highlights segments of buffer text whose reordering for display is
 suspicious and could be malicious.
 
 
+
+** Emacs server and client changes
+
++++
+*** New command-line option '-r' for emacsclient.
+With this command-line option, Emacs reuses an existing graphical client
+frame if one exists; otherwise a new frame is created.
+
 * Editing Changes in Emacs 29.1
 
 ---
diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index cff3cec2a79..0e800dd7e89 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -116,6 +116,9 @@ static bool eval;
 /* 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 @@ static struct option const longopts[] =
   { "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 @@ The following OPTIONS are accepted:\n\
 -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)
-- 
2.39.2