bug#81666: 31.1; browse-url fails in emacsclient -nw

> From: Abdulnafé Toulaïmat
>  <[email protected]>
> Date: Thu, 20 Aug 2026 21:53:24 +0200
> 
> ‘browse-url’ gives an error "funcall-interactively: Frames are not in use or
> not initialized", but only when called in an emacsclient TTY frame. It
> works fine in GUI frames, for both emacs and emacsclient, as well as in
> emacs TTY frames.
> 
> Steps to reproduce:
> 
> 1) emacs --daemon -Q
> 2) emacsclient -nw
> 3) M-x browse-url RET
> 4) https://www.gnu.org/software/emacs/ RET
> 
> With ‘toggle-debug-on-error’, I get this trace:
> 
> --8<---------------cut here---------------start------------->8---
> Debugger entered--Lisp error: (error "Frames are not in use or not initialized")
>   browse-url("https://www.gnu.org/software/emacs/" nil)
>   funcall-interactively(browse-url "https://www.gnu.org/software/emacs/" nil)
>   command-execute(browse-url record)
>   #<subr execute-extended-command>(nil "browse-url" nil)
>   apply(#<subr execute-extended-command> (nil "browse-url" nil))
>   execute-extended-command(nil "browse-url" nil)
>   funcall-interactively(execute-extended-command nil "browse-url" nil)
>   command-execute(execute-extended-command)
> --8<---------------cut here---------------end--------------->8---

This error is specific to a PGTK build, and comes from browse-url here:

    ;; When connected to various displays, be careful to use the display of
    ;; the currently selected frame, rather than the original start display,
    ;; which may not even exist any more.
    (let ((dpy (frame-parameter nil 'display))
          classname)
      (if (stringp dpy)
        (cond
         ((featurep 'pgtk)
          (setq classname (pgtk-backend-display-class))  <<<<<<<<<<<<<<<
          (if (equal classname "GdkWaylandDisplay")
              (progn
                ;; The `display' frame parameter is probably wrong.
                ;; See bug#53969 for some context.
                ;; (setenv "WAYLAND_DISPLAY" dpy)
                )
            (setenv "DISPLAY" dpy)))

All this is conditioned on "(frame-parameter nil 'display)" returning
a string, which AFAIU is not expected in the -nw case.  So the first
question is: what does "(frame-parameter nil 'display)" yield in your
case, in the scenario you describe, just before you invoke browse-url
from the client frame?

(FWIW, I tried to reproduce this in a PGTK build I have here, but
couldn't: I see no error in this case.  And frame-parameter returns
nil in my case, as expected.)