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

> Cc: [email protected], [email protected], [email protected],
>  [email protected], [email protected], [email protected]
> Date: Fri, 21 Aug 2026 15:19:28 +0300
> From: Eli Zaretskii <[email protected]>
> 
> > >> > (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.)
> > >>
> > >> Hello, thanks for looking into this.
> > >>
> > >> In the emacsclient TTY frame, I get ":0". This does indeed appear to be
> > >> the main culprit, because in an *emacs* TTY frame, I get nil, as you
> > >> describe.
> > 
> > With some grepping it appears to be because of commit:
> > e2b64f8999f79a5820ba00d2987885d7dda492d5
> > 
> > which solves bug#54844
> 
> Thanks, but I still don't see why this should cause the problem in the
> PGTK builds.  That change only affects GUI frames, or at least that's
> my reading of the code.

In any case, I propose the patch below.  Abdulnafé Toulaïmat, can you
please see if it solves your problem?

diff --git a/lisp/net/browse-url.el b/lisp/net/browse-url.el
index b6513d1..ca91736 100644
--- a/lisp/net/browse-url.el
+++ b/lisp/net/browse-url.el
@@ -932,7 +932,9 @@ browse-url
       (if (stringp dpy)
         (cond
          ((featurep 'pgtk)
-          (setq classname (pgtk-backend-display-class))
+          (setq classname
+                (if (window-system)
+                    (pgtk-backend-display-class)))
           (if (equal classname "GdkWaylandDisplay")
               (progn
                 ;; The `display' frame parameter is probably wrong.