bug#26995: 26.0.50; emacsclient --tty FILE flashes previous frame's buffer before loading FILE

[Aaron Jensen <aaronjensen@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 951 bytes --]

From: Eli Zaretskii (mailto:eliz@gnu.org)
> > From: Aaron Jensen
> > > I can indeed reproduce the described behavior, but I see the same in
> > > Emacs 25.2 and in Emacs 24.5. The reason is simple: the way server.el
> > > is written, we first create the client frame, and only then show the
> > > file there. So the frame is created with no file to visit, and Emacs
> > > always shows the last buffer in the new frame in those cases.
> >
> > I see, so not a bug then. Is it possible to (easily) improve its behavior?
>
> It should be possible, but AFAICT it would need restructuring
> server-process-filter works.

Please see attached patch and let me know if this method is
acceptable. It’s perhaps a little kludgy because sometimes a frame is
created and sometimes it isn’t so we need both methods of ensuring the
initial frame is set properly. This does appear to work for all
scenarios I tested, however.

Thanks,

Aaron

[-- Attachment #2: 0001-Show-initial-buffer-immediately-upon-frame-creation-.patch --]
[-- Type: application/octet-stream, Size: 5488 bytes --]

From e1a8f19c5ec119202a2df934bf3175e2a4fdd4a8 Mon Sep 17 00:00:00 2001
From: Aaron Jensen <aaronjensen@gmail.com>
Date: Sun, 4 Feb 2018 22:52:48 -0800
Subject: [PATCH] Show initial buffer immediately upon frame creation from
 server

---
 lisp/server.el | 85 ++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 47 insertions(+), 38 deletions(-)

diff --git a/lisp/server.el b/lisp/server.el
index ac0d701851..f7766a0253 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -1229,28 +1229,29 @@ server-execute-continuation
 		 (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
+                  (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
@@ -1262,7 +1263,7 @@ server-execute-continuation
                          (if (and dir (file-directory-p dir))
                              dir default-directory)))
                    (server-execute proc files nowait commands
-                                   dontkill frame tty-name)))))
+                                   dontkill create-frame tty-name)))))
 
             (when (or frame files)
               (server-goto-toplevel proc))
@@ -1271,7 +1272,7 @@ server-execute-continuation
     ;; 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 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
@@ -1281,21 +1282,29 @@ server-execute
   ;; 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)
+                          ;; 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
-- 
2.15.1