eww: Use browse-url-with-browser-kind in eww-browse-with-external-browser

Guarantee that an external browser is used by EWW if
`browse-url-secondary-browser-function' is set to
`eww-browse-url'.
* lisp/net/eww.el (eww-browse-with-external-browser): Use
`browse-url-secondary-browser-function' only if it is an
external browser, otherwise fall back to
`browse-url-with-browser-kind'.
(eww-follow-link): Use `eww-browse-with-external-browser' if the
EXTERNAL prefix argument is non-nil.  Improve docstring.
* lisp/net/browse-url.el (browse-url-secondary-browser-function):
Update docstring.  (Bug#74730)

2 files changed, 24 insertions, 13 deletions

diff --git a/lisp/net/browse-url.el b/lisp/net/browse-url.el
index a4de177f972..de2fa9c2bfb 100644
--- a/lisp/net/browse-url.el
+++ b/lisp/net/browse-url.el
@@ -198,10 +198,16 @@ Also see `browse-url-secondary-browser-function' and
 
 (defcustom browse-url-secondary-browser-function 'browse-url-default-browser
   "Function used to launch an alternative browser.
-This is usually an external browser (that is, not eww or w3m),
-used as the secondary browser choice, typically when a prefix
-argument is given to a URL-opening command in those modes that
-support this (for instance, eww/shr).
+
+This browser is used as the secondary browser choice, typically
+when a prefix argument is given to a URL-opening command in those
+modes that support this (for instance `browse-url-at-point',
+`goto-addr-at-point', eww or shr).
+
+This assumption is that `browse-url-secondary-browser-function'
+and `browse-url-browser-function' are set to distinct browsers.
+Either one of the two functions should call an external browser
+and the other one should not do the same.
 
 Also see `browse-url-browser-function'."
   :version "27.1"
diff --git a/lisp/net/eww.el b/lisp/net/eww.el
index 4d4d4d6beac..4609755a902 100644
--- a/lisp/net/eww.el
+++ b/lisp/net/eww.el
@@ -2142,11 +2142,15 @@ Interactively, EVENT is the value of `last-nonmenu-event'."
 
 (defun eww-browse-with-external-browser (&optional url)
   "Browse the current URL with an external browser.
-The browser to used is specified by the
-`browse-url-secondary-browser-function' variable."
+Use `browse-url-secondary-browser-function' if it is an external
+browser, otherwise use `browse-url-with-browser-kind' to open an
+external browser."
   (interactive nil eww-mode)
-  (funcall browse-url-secondary-browser-function
-           (or url (plist-get eww-data :url))))
+  (setq url (or url (plist-get eww-data :url)))
+  (if (eq 'external (browse-url--browser-kind
+                     browse-url-secondary-browser-function url))
+      (funcall browse-url-secondary-browser-function url)
+    (browse-url-with-browser-kind 'external url)))
 
 (defun eww-remove-tracking (url)
   "Remove the commong utm_ tracking cookies from URLs."
@@ -2160,11 +2164,12 @@ The browser to used is specified by the
     url))
 
 (defun eww-follow-link (&optional external mouse-event)
-  "Browse the URL under point.
-If EXTERNAL is single prefix, browse the URL using
-`browse-url-secondary-browser-function'.
+  "Browse the URL at point, optionally the position of MOUSE-EVENT.
 
-If EXTERNAL is double prefix, browse in new buffer."
+EXTERNAL is the prefix argument.  If called interactively with
+\\[universal-argument] pressed once, browse the URL using
+`eww-browse-with-external-browser'.  If called interactively, with
+\\[universal-argument] pressed twice, browse in new buffer."
   (interactive
    (list current-prefix-arg last-nonmenu-event)
    eww-mode)
@@ -2180,7 +2185,7 @@ If EXTERNAL is double prefix, browse in new buffer."
       ;; and `browse-url-mailto-function'.
       (browse-url url))
      ((and (consp external) (<= (car external) 4))
-      (funcall browse-url-secondary-browser-function url)
+      (eww-browse-with-external-browser url)
       (shr--blink-link))
      ;; This is a #target url in the same page as the current one.
      ((and (setq target (url-target (url-generic-parse-url url)))