Don't flash previous buffer when connecting with emacsclient

* lisp/server.el (server-execute): Accept lambda for creating
frame rather than frame.  Ensure newly created tty frame
initially shows the correct buffer.
(server-process-filter): Pass a lambda to server-execute to create
a frame.  (Bug#24218)

1 files changed, 49 insertions, 39 deletions

diff --git a/lisp/server.el b/lisp/server.el
index d3933883cf7..a892203c24a 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -1092,7 +1092,8 @@ The following commands are accepted by the client:
                 tty-type   ; string.
                 files
                 filepos
-                args-left)
+                args-left
+                create-frame-func)
             ;; Remove this line from STRING.
             (setq string (substring string (match-end 0)))
             (setq args-left
@@ -1244,28 +1245,29 @@ The following commands are accepted by the client:
                  (or files commands)
                  (setq use-current-frame t))
 
-            (setq frame
-                  (cond
-                   ((and use-current-frame
-                         (or (eq use-current-frame 'always)
-                             ;; We can't use the Emacs daemon's
-                             ;; terminal frame.
-                             (not (and (daemonp)
-                                       (null (cdr (frame-list)))
-                                       (eq (selected-frame)
-                                           terminal-frame)))))
-                    (setq tty-name nil tty-type nil)
-                    (if display (server-select-display display)))
-                   ((or (and (eq system-type 'windows-nt)
-                             (daemonp)
-                             (setq display "w32"))
-                        (eq tty-name 'window-system))
-                    (server-create-window-system-frame display nowait proc
-                                                       parent-id
-                                                       frame-parameters))
-                   ;; When resuming on a tty, tty-name is nil.
-                   (tty-name
-                    (server-create-tty-frame tty-name tty-type proc))))
+            (setq create-frame-func
+                  (lambda ()
+                    (cond
+                     ((and use-current-frame
+                           (or (eq use-current-frame 'always)
+                               ;; We can't use the Emacs daemon's
+                               ;; terminal frame.
+                               (not (and (daemonp)
+                                         (null (cdr (frame-list)))
+                                         (eq (selected-frame)
+                                             terminal-frame)))))
+                      (setq tty-name nil tty-type nil)
+                      (if display (server-select-display display)))
+                     ((or (and (eq system-type 'windows-nt)
+                               (daemonp)
+                               (setq display "w32"))
+                          (eq tty-name 'window-system))
+                      (server-create-window-system-frame display nowait proc
+                                                    parent-id
+                                                    frame-parameters))
+                     ;; When resuming on a tty, tty-name is nil.
+                     (tty-name
+                      (server-create-tty-frame tty-name tty-type proc)))))
 
             (process-put
              proc 'continuation
@@ -1277,7 +1279,7 @@ The following commands are accepted by the client:
                          (if (and dir (file-directory-p dir))
                              dir default-directory)))
                    (server-execute proc files nowait commands
-                                   dontkill frame tty-name)))))
+                                   dontkill create-frame-func tty-name)))))
 
             (when (or frame files)
               (server-goto-toplevel proc))
@@ -1286,7 +1288,7 @@ The following commands are accepted by the client:
     ;; condition-case
     (error (server-return-error proc err))))
 
-(defun server-execute (proc files nowait commands dontkill frame tty-name)
+(defun server-execute (proc files nowait commands dontkill create-frame-func tty-name)
   ;; This is run from timers and process-filters, i.e. "asynchronously".
   ;; But w.r.t the user, this is not really asynchronous since the timer
   ;; is run after 0s and the process-filter is run in response to the
@@ -1296,21 +1298,29 @@ The following commands are accepted by the client:
   ;; including code that needs to wait.
   (with-local-quit
     (condition-case err
-        (let ((buffers (server-visit-files files proc nowait)))
-          (mapc 'funcall (nreverse commands))
+        (let* ((buffers (server-visit-files files proc nowait))
+               ;; If we were told only to open a new client, obey
+               ;; `initial-buffer-choice' if it specifies a file
+               ;; or a function.
+               (initial-buffer (unless (or files commands)
+                                 (let ((buf
+                                        (cond ((stringp initial-buffer-choice)
+                                               (find-file-noselect initial-buffer-choice))
+                                              ((functionp initial-buffer-choice)
+                                               (funcall initial-buffer-choice)))))
+                                   (if (buffer-live-p buf) buf (get-buffer-create "*scratch*")))))
+               ;; Set current buffer so that newly created tty frames
+               ;; show the correct buffer initially.
+               (frame (with-current-buffer (or (car buffers)
+                                               initial-buffer
+                                               (current-buffer))
+                        (prog1
+                            (funcall create-frame-func)
+                          ;; Switch to initial buffer in case the frame was reused.
+                          (when initial-buffer
+                            (switch-to-buffer initial-buffer 'norecord))))))
 
-          ;; If we were told only to open a new client, obey
-          ;; `initial-buffer-choice' if it specifies a file
-          ;; or a function.
-          (unless (or files commands)
-            (let ((buf
-                   (cond ((stringp initial-buffer-choice)
-                          (find-file-noselect initial-buffer-choice))
-                         ((functionp initial-buffer-choice)
-                          (funcall initial-buffer-choice)))))
-              (switch-to-buffer
-               (if (buffer-live-p buf) buf (get-buffer-create "*scratch*"))
-               'norecord)))
+          (mapc 'funcall (nreverse commands))
 
           ;; Delete the client if necessary.
           (cond