bug#28340: 26.0.50; xterm frame titles

[Mark Oteiza <mvoteiza@udel.edu>]

On 20/09/17 at 07:47am, Eli Zaretskii wrote:
> > Date: Mon, 11 Sep 2017 21:21:22 -0400
> > From: Mark Oteiza <mvoteiza@udel.edu>
> > Cc: 28340@debbugs.gnu.org
> > 
> > > Maybe one of the hooks provided by server.el would fit the bill?
> > 
> > Nope, none of those appear relevant, and hooking into them does nothing
> > apparent.  Even doing the following, I get the title as the selected
> > buffer in the previously selected frame.
> > 
> > Messaging (frame-list) in xterm-test shows that the car of the list is
> > always the new frame, but still the frame title is incorrect--a new
> > frame created by emacsclient -t ends up on the scratch buffer.  I say
> > "ends up" because sometimes I see another buffer flash before I see the
> > scratch buffer.  This all seems a little buggy to me, but I know
> > Bug#18137 and its ancestors were tough.
> 
> What about window-configuration-change-hook, does that help?  You
> could set some flag in after-make-frame-functions, and then test and
> reset that flag in window-configuration-change-hook, when you see that
> a buffer is switched in the frame.  Would that work?

This appears to work, thank you.  Please see attached.


diff --git a/lisp/term/xterm.el b/lisp/term/xterm.el
index 4f79703833..a11acbc4db 100644
--- a/lisp/term/xterm.el
+++ b/lisp/term/xterm.el
@@ -68,6 +68,11 @@ xterm-max-cut-length
   :version "25.1"
   :type 'integer)
 
+(defcustom xterm-set-window-title t
+  "Whether Emacs should set window titles to an Emacs frame in an XTerm."
+  :version "27.1"
+  :type 'boolean)
+
 (defconst xterm-paste-ending-sequence "\e[201~"
   "Characters send by the terminal to end a bracketed paste.")
 
@@ -802,6 +807,8 @@ terminal-init-xterm
     (when (memq 'setSelection xterm-extra-capabilities)
       (xterm--init-activate-set-selection)))
 
+  (when xterm-set-window-title
+    (xterm--init-frame-title))
   ;; Unconditionally enable bracketed paste mode: terminals that don't
   ;; support it just ignore the sequence.
   (xterm--init-bracketed-paste-mode)
@@ -828,6 +835,31 @@ xterm--init-activate-set-selection
   "Terminal initialization for `gui-set-selection'."
   (set-terminal-parameter nil 'xterm--set-selection t))
 
+(defun xterm--init-frame-title ()
+  "Terminal initialization for `gui-set-selection'."
+  (xterm-set-window-title)
+  (add-hook 'after-make-frame-functions 'xterm-set-window-title-flag)
+  (add-hook 'window-configuration-change-hook 'xterm-unset-window-title-flag)
+  (add-hook 'post-command-hook 'xterm-set-window-title)
+  (add-hook 'minibuffer-exit-hook 'xterm-set-window-title))
+
+(defvar xterm-window-title-flag nil
+  "Whether the a new frame has been created, calling for a title update.")
+
+(defun xterm-set-window-title-flag (_frame)
+  (setq xterm-window-title-flag t))
+
+(defun xterm-unset-window-title-flag ()
+  (when xterm-window-title-flag
+    (setq xterm-window-title-flag nil)
+    (xterm-set-window-title)))
+
+(defun xterm-set-window-title (&optional terminal)
+  "Set the window title of the Xterm with the current Emacs frame."
+  (send-string-to-terminal
+   (format "\e]2;%s\a" (format-mode-line frame-title-format))
+   terminal))
+
 (defun xterm--selection-char (type)
   (pcase type
     ('PRIMARY "p")