How does one set input-decode-map on GUI frames in emacsclient?

Question

I'm trying to adjust bindings in input-decode-map (to distinguish C-m and RET in GUI mode). None of the advice given on Stack Overflow, gnu.emacs.help, Reddit, or Super User seems to work. I ended up with this:

(defun ~/setup-C-m (&rest args)
  (define-key input-decode-map [?\C-m] [C-m]))

(~/setup-C-m)
(add-hook 'tty-setup-hook #'~/setup-C-m)
(add-hook 'window-setup-hook #'~/setup-C-m)
(add-hook 'terminal-init-xterm-hook #'~/setup-C-m)
(add-hook 'after-make-frame-functions #'~/setup-C-m)

Even with all these, starting Emacs with emacsclient --alternate-editor="" --create-frame --frame-parameters="((fullscreen . maximized))" results in input-decode-map being set to this:

Value:
(keymap
 (27 keymap
     (C-backspace)
     (C-delete))
 (C-M-backspace)
 (C-M-delete)
 (M-backspace)
 (M-delete))

Which doesn't include the C-m binding. I've printed the value of input-decode-map when my setup-C-m function is called, and it's always an empty keymap.

How can I ensure that my setup-C-m function runs every time I create a frame and properly sets input-decode-map?

Answer 1

Your usage of after-make-frame-functions isn't working because you're ignoring the FRAME argument, and therefore not operating on the new frame at all.

Your function needs to do this:

(with-selected-frame FRAME
  ...)

Answer 2

(add-hook 'server-after-make-frame-hook #'~/setup-C-m) should do what you want (at least since 27.1).