Enable browse-url to buttonize buffers

This patch also moves the internal/external browser logic from
shr to browse-url, where it belongs more naturally.

* doc/misc/eww.texi (Basics): Adjust to browse-url-external-browser.

* doc/misc/gnus.texi (Article Commands): Ditto.

* lisp/gnus/gnus-art.el (gnus-button-url-regexp): Default to
`browse-url-button-regexp', which has taken over the definition
previously enjoyed by this variable.

* lisp/gnus/gnus-sum.el (gnus-summary-browse-url): Adjust usage.

* lisp/net/browse-url.el (browse-url--browser-defcustom-type): New
internal variable...
(browse-url-browser-function, browse-url-external-browser): Used
by these two; the latter of which is a new variable.
(browse-url-botton-regexp): New variable.
(browse-url-button-map): New keymap.
(browse-url-button): New face.
(browse-url-add-buttons): New function to add clickable browse-url
buttons to almost any buffer.
(browse-url-button-open): New command.
(browse-url-button-copy): New command.

* lisp/net/eww.el (eww-browse-with-external-browser)
(eww-follow-link): Adjust usage.

* lisp/net/shr.el (shr-external-browser): Make an obsolete alias
of `browse-url-external-browser'.
(shr-browse-url): Adjust usage.

1 files changed, 168 insertions, 142 deletions

diff --git a/lisp/net/browse-url.el b/lisp/net/browse-url.el
index aa31e25fa91..17b6d36ca87 100644
--- a/lisp/net/browse-url.el
+++ b/lisp/net/browse-url.el
@@ -131,9 +131,36 @@
   :group 'external
   :group 'comm)
 
+(defvar browse-url--browser-defcustom-type
+  '(choice
+    (function-item :tag "Emacs W3" :value  browse-url-w3)
+    (function-item :tag "eww" :value  eww-browse-url)
+    (function-item :tag "Mozilla" :value  browse-url-mozilla)
+    (function-item :tag "Firefox" :value browse-url-firefox)
+    (function-item :tag "Google Chrome" :value browse-url-chrome)
+    (function-item :tag "Chromium" :value browse-url-chromium)
+    (function-item :tag "Epiphany" :value  browse-url-epiphany)
+    (function-item :tag "Conkeror" :value  browse-url-conkeror)
+    (function-item :tag "Text browser in an xterm window"
+		   :value browse-url-text-xterm)
+    (function-item :tag "Text browser in an Emacs window"
+		   :value browse-url-text-emacs)
+    (function-item :tag "KDE" :value browse-url-kde)
+    (function-item :tag "Elinks" :value browse-url-elinks)
+    (function-item :tag "Specified by `Browse Url Generic Program'"
+		   :value browse-url-generic)
+    (function-item :tag "Default Windows browser"
+		   :value browse-url-default-windows-browser)
+    (function-item :tag "Default macOS browser"
+		   :value browse-url-default-macosx-browser)
+    (function-item :tag "Default browser"
+		   :value browse-url-default-browser)
+    (function :tag "Your own function")
+    (alist :tag "Regexp/function association list"
+	   :key-type regexp :value-type function)))
+
 ;;;###autoload
-(defcustom browse-url-browser-function
-  'browse-url-default-browser
+(defcustom browse-url-browser-function 'browse-url-default-browser
   "Function to display the current buffer in a WWW browser.
 This is used by the `browse-url-at-point', `browse-url-at-mouse', and
 `browse-url-of-file' commands.
@@ -143,34 +170,17 @@ If the value is not a function it should be a list of pairs
 associated with the first REGEXP which matches the current URL.  The
 function is passed the URL and any other args of `browse-url'.  The last
 regexp should probably be \".\" to specify a default browser."
-  :type '(choice
-	  (function-item :tag "Emacs W3" :value  browse-url-w3)
-	  (function-item :tag "eww" :value  eww-browse-url)
-	  (function-item :tag "Mozilla" :value  browse-url-mozilla)
-	  (function-item :tag "Firefox" :value browse-url-firefox)
-	  (function-item :tag "Google Chrome" :value browse-url-chrome)
-	  (function-item :tag "Chromium" :value browse-url-chromium)
-	  (function-item :tag "Epiphany" :value  browse-url-epiphany)
-	  (function-item :tag "Conkeror" :value  browse-url-conkeror)
-	  (function-item :tag "Text browser in an xterm window"
-			 :value browse-url-text-xterm)
-	  (function-item :tag "Text browser in an Emacs window"
-			 :value browse-url-text-emacs)
-	  (function-item :tag "KDE" :value browse-url-kde)
-	  (function-item :tag "Elinks" :value browse-url-elinks)
-	  (function-item :tag "Specified by `Browse Url Generic Program'"
-			 :value browse-url-generic)
-	  (function-item :tag "Default Windows browser"
-			 :value browse-url-default-windows-browser)
-	  (function-item :tag "Default macOS browser"
-			 :value browse-url-default-macosx-browser)
-	  (function-item :tag "Default browser"
-			 :value browse-url-default-browser)
-	  (function :tag "Your own function")
-	  (alist :tag "Regexp/function association list"
-		 :key-type regexp :value-type function))
-  :version "24.1"
-  :group 'browse-url)
+  :type browse-url--browser-defcustom-type
+  :version "24.1")
+
+(defcustom browse-url-external-browser 'browse-url-default-browser
+  "Function used to launch an external browser.
+This can actually be any browser, internal or external, used as
+the secondary browser choice, and is typically used when giving a
+prefix argument to the URL-opening command (in those modes that
+support this (for instance, eww/shr)."
+  :version "27.1"
+  :type browse-url--browser-defcustom-type)
 
 (defcustom browse-url-mailto-function 'browse-url-mail
   "Function to display mailto: links.
@@ -181,8 +191,7 @@ be used instead."
   :type '(choice
 	  (function-item :tag "Emacs Mail" :value browse-url-mail)
 	  (function-item :tag "None" nil))
-  :version "24.1"
-  :group 'browse-url)
+  :version "24.1")
 
 (defcustom browse-url-man-function 'browse-url-man
   "Function to display man: links."
@@ -190,8 +199,28 @@ be used instead."
           (function-item :tag "Emacs Man" :value browse-url-man)
           (const :tag "None" nil)
           (function :tag "Other function"))
-  :version "26.1"
-  :group 'browse-url)
+  :version "26.1")
+
+(defcustom browse-url-button-regexp
+  (concat
+   "\\b\\(\\(www\\.\\|\\(s?https?\\|ftp\\|file\\|gopher\\|"
+   "nntp\\|news\\|telnet\\|wais\\|mailto\\|info\\):\\)"
+   "\\(//[-a-z0-9_.]+:[0-9]*\\)?"
+   (let ((chars "-a-z0-9_=#$@~%&*+\\/[:word:]")
+	 (punct "!?:;.,"))
+     (concat
+      "\\(?:"
+      ;; Match paired parentheses, e.g. in Wikipedia URLs:
+      ;; http://thread.gmane.org/47B4E3B2.3050402@gmail.com
+      "[" chars punct "]+" "(" "[" chars punct "]+" "[" chars "]*)"
+      "\\(?:" "[" chars punct "]+" "[" chars "]" "\\)?"
+      "\\|"
+      "[" chars punct "]+" "[" chars "]"
+      "\\)"))
+   "\\)")
+  "Regular expression that matches URLs."
+  :version "27.1"
+  :type 'regexp)
 
 (defcustom browse-url-netscape-program "netscape"
   ;; Info about netscape-remote from Karl Berry.
@@ -202,15 +231,13 @@ The free program `netscape-remote' from
 up very much quicker than `netscape'.  Reported to compile on a GNU
 system, given vroot.h from the same directory, with cc flags
  -DSTANDALONE -L/usr/X11R6/lib -lXmu -lX11."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (make-obsolete-variable 'browse-url-netscape-program nil "25.1")
 
 (defcustom browse-url-netscape-arguments nil
   "A list of strings to pass to Netscape as arguments."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (make-obsolete-variable 'browse-url-netscape-arguments nil "25.1")
 
@@ -218,33 +245,27 @@ system, given vroot.h from the same directory, with cc flags
   "A list of strings to pass to Netscape when it starts up.
 Defaults to the value of `browse-url-netscape-arguments' at the time
 `browse-url' is loaded."
-  :type '(repeat (string :tag "Argument"))
-
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (make-obsolete-variable 'browse-url-netscape-startup-arguments nil "25.1")
 
 (defcustom browse-url-browser-display nil
   "The X display for running the browser, if not same as Emacs's."
-  :type '(choice string (const :tag "Default" nil))
-  :group 'browse-url)
+  :type '(choice string (const :tag "Default" nil)))
 
 (defcustom browse-url-mozilla-program "mozilla"
   "The name by which to invoke Mozilla."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (defcustom browse-url-mozilla-arguments nil
   "A list of strings to pass to Mozilla as arguments."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-mozilla-startup-arguments browse-url-mozilla-arguments
   "A list of strings to pass to Mozilla when it starts up.
 Defaults to the value of `browse-url-mozilla-arguments' at the time
 `browse-url' is loaded."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-firefox-program
   (let ((candidates '("icecat" "iceweasel" "firefox")))
@@ -252,20 +273,17 @@ Defaults to the value of `browse-url-mozilla-arguments' at the time
       (setq candidates (cdr candidates)))
     (or (car candidates) "firefox"))
   "The name by which to invoke Firefox or a variant of it."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (defcustom browse-url-firefox-arguments nil
   "A list of strings to pass to Firefox (or variant) as arguments."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-firefox-startup-arguments browse-url-firefox-arguments
   "A list of strings to pass to Firefox (or variant) when it starts up.
 Defaults to the value of `browse-url-firefox-arguments' at the time
 `browse-url' is loaded."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (make-obsolete-variable 'browse-url-firefox-startup-arguments
                         "it no longer has any effect." "24.5")
@@ -277,14 +295,12 @@ Defaults to the value of `browse-url-firefox-arguments' at the time
     (or (car candidates) "chromium"))
   "The name by which to invoke the Chrome browser."
   :type 'string
-  :version "25.1"
-  :group 'browse-url)
+  :version "25.1")
 
 (defcustom browse-url-chrome-arguments nil
   "A list of strings to pass to Google Chrome as arguments."
   :type '(repeat (string :tag "Argument"))
-  :version "25.1"
-  :group 'browse-url)
+  :version "25.1")
 
 (defcustom browse-url-chromium-program
   (let ((candidates '("chromium" "chromium-browser")))
@@ -293,26 +309,22 @@ Defaults to the value of `browse-url-firefox-arguments' at the time
     (or (car candidates) "chromium"))
   "The name by which to invoke Chromium."
   :type 'string
-  :version "24.1"
-  :group 'browse-url)
+  :version "24.1")
 
 (defcustom browse-url-chromium-arguments nil
   "A list of strings to pass to Chromium as arguments."
   :type '(repeat (string :tag "Argument"))
-  :version "24.1"
-  :group 'browse-url)
+  :version "24.1")
 
 (defcustom browse-url-galeon-program "galeon"
   "The name by which to invoke Galeon."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (make-obsolete-variable 'browse-url-galeon-program nil "25.1")
 
 (defcustom browse-url-galeon-arguments nil
   "A list of strings to pass to Galeon as arguments."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (make-obsolete-variable 'browse-url-galeon-arguments nil "25.1")
 
@@ -320,27 +332,23 @@ Defaults to the value of `browse-url-firefox-arguments' at the time
   "A list of strings to pass to Galeon when it starts up.
 Defaults to the value of `browse-url-galeon-arguments' at the time
 `browse-url' is loaded."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (make-obsolete-variable 'browse-url-galeon-startup-arguments nil "25.1")
 
 (defcustom browse-url-epiphany-program "epiphany"
   "The name by which to invoke Epiphany."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (defcustom browse-url-epiphany-arguments nil
   "A list of strings to pass to Epiphany as arguments."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-epiphany-startup-arguments browse-url-epiphany-arguments
   "A list of strings to pass to Epiphany when it starts up.
 Defaults to the value of `browse-url-epiphany-arguments' at the time
 `browse-url' is loaded."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 ;; GNOME means of invoking either Mozilla or Netscape.
 (defvar browse-url-gnome-moz-program "gnome-moz-remote")
@@ -350,8 +358,7 @@ Defaults to the value of `browse-url-epiphany-arguments' at the time
 (defcustom browse-url-gnome-moz-arguments '()
   "A list of strings passed to the GNOME mozilla viewer as arguments."
   :version "21.1"
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (make-obsolete-variable 'browse-url-gnome-moz-arguments nil "25.1")
 
@@ -359,30 +366,26 @@ Defaults to the value of `browse-url-epiphany-arguments' at the time
   "Whether to open up new windows in a tab or a new window.
 If non-nil, then open the URL in a new tab rather than a new window if
 `browse-url-mozilla' is asked to open it in a new window."
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (defcustom browse-url-firefox-new-window-is-tab nil
   "Whether to open up new windows in a tab or a new window.
 If non-nil, then open the URL in a new tab rather than a new window if
 `browse-url-firefox' is asked to open it in a new window."
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (defcustom browse-url-conkeror-new-window-is-buffer nil
   "Whether to open up new windows in a buffer or a new window.
 If non-nil, then open the URL in a new buffer rather than a new window if
 `browse-url-conkeror' is asked to open it in a new window."
   :version "25.1"
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (defcustom browse-url-galeon-new-window-is-tab nil
   "Whether to open up new windows in a tab or a new window.
 If non-nil, then open the URL in a new tab rather than a new window if
 `browse-url-galeon' is asked to open it in a new window."
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (make-obsolete-variable 'browse-url-galeon-new-window-is-tab nil "25.1")
 
@@ -390,16 +393,14 @@ If non-nil, then open the URL in a new tab rather than a new window if
   "Whether to open up new windows in a tab or a new window.
 If non-nil, then open the URL in a new tab rather than a new window if
 `browse-url-epiphany' is asked to open it in a new window."
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (defcustom browse-url-netscape-new-window-is-tab nil
   "Whether to open up new windows in a tab or a new window.
 If non-nil, then open the URL in a new tab rather than a new
 window if `browse-url-netscape' is asked to open it in a new
 window."
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (make-obsolete-variable 'browse-url-netscape-new-window-is-tab nil "25.1")
 
@@ -407,42 +408,36 @@ window."
   "Non-nil means always open a new browser window with appropriate browsers.
 Passing an interactive argument to \\[browse-url], or specific browser
 commands reverses the effect of this variable."
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (defcustom browse-url-mosaic-program "xmosaic"
   "The name by which to invoke Mosaic (or mMosaic)."
   :type 'string
-  :version "20.3"
-  :group 'browse-url)
+  :version "20.3")
 
 (make-obsolete-variable 'browse-url-mosaic-program nil "25.1")
 
 (defcustom browse-url-mosaic-arguments nil
   "A list of strings to pass to Mosaic as arguments."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (make-obsolete-variable 'browse-url-mosaic-arguments nil "25.1")
 
 (defcustom browse-url-mosaic-pidfile "~/.mosaicpid"
   "The name of the pidfile created by Mosaic."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (make-obsolete-variable 'browse-url-mosaic-pidfile nil "25.1")
 
 (defcustom browse-url-conkeror-program "conkeror"
   "The name by which to invoke Conkeror."
   :type 'string
-  :version "25.1"
-  :group 'browse-url)
+  :version "25.1")
 
 (defcustom browse-url-conkeror-arguments nil
   "A list of strings to pass to Conkeror as arguments."
   :version "25.1"
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-filename-alist
   `(("^/\\(ftp@\\|anonymous@\\)?\\([^:/]+\\):/*" . "ftp://\\2/")
@@ -473,26 +468,22 @@ address to an HTTP URL:
   :type '(repeat (cons :format "%v"
                        (regexp :tag "Regexp")
                        (string :tag "Replacement")))
-  :version "25.1"
-  :group 'browse-url)
+  :version "25.1")
 
 (defcustom browse-url-save-file nil
   "If non-nil, save the buffer before displaying its file.
 Used by the `browse-url-of-file' command."
-  :type 'boolean
-  :group 'browse-url)
+  :type 'boolean)
 
 (defcustom browse-url-of-file-hook nil
   "Hook run after `browse-url-of-file' has asked a browser to load a file."
-  :type 'hook
-  :group 'browse-url)
+  :type 'hook)
 
 (defcustom browse-url-CCI-port 3003
   "Port to access XMosaic via CCI.
 This can be any number between 1024 and 65535 but must correspond to
 the value set in the browser."
-  :type 'integer
-  :group 'browse-url)
+  :type 'integer)
 
 (make-obsolete-variable 'browse-url-CCI-port nil "25.1")
 
@@ -500,8 +491,7 @@ the value set in the browser."
   "Host to access XMosaic via CCI.
 This should be the host name of the machine running XMosaic with CCI
 enabled.  The port number should be set in `browse-url-CCI-port'."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (make-obsolete-variable 'browse-url-CCI-host nil "25.1")
 
@@ -511,57 +501,48 @@ enabled.  The port number should be set in `browse-url-CCI-port'."
 (defcustom browse-url-xterm-program "xterm"
   "The name of the terminal emulator used by `browse-url-text-xterm'.
 This might, for instance, be a separate color version of xterm."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (defcustom browse-url-xterm-args nil
   "A list of strings defining options for `browse-url-xterm-program'.
 These might set its size, for instance."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-gnudoit-program "gnudoit"
   "The name of the `gnudoit' program used by `browse-url-w3-gnudoit'."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (defcustom browse-url-gnudoit-args '("-q")
   "A list of strings defining options for `browse-url-gnudoit-program'.
 These might set the port, for instance."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-generic-program nil
   "The name of the browser program used by `browse-url-generic'."
-  :type '(choice string (const :tag "None" nil))
-  :group 'browse-url)
+  :type '(choice string (const :tag "None" nil)))
 
 (defcustom browse-url-generic-args nil
   "A list of strings defining options for `browse-url-generic-program'."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-temp-dir temporary-file-directory
   "The name of a directory for browse-url's temporary files.
 Such files are generated by functions like `browse-url-of-region'.
 You might want to set this to somewhere with restricted read permissions
 for privacy's sake."
-  :type 'string
-  :group 'browse-url)
+  :type 'string)
 
 (defcustom browse-url-netscape-version 3
   "The version of Netscape you are using.
 This affects how URL reloading is done; the mechanism changed
 incompatibly at version 4."
-  :type 'number
-  :group 'browse-url)
+  :type 'number)
 
 (make-obsolete-variable 'browse-url-netscape-version nil "25.1")
 
 (defcustom browse-url-text-browser "lynx"
   "The name of the text browser to invoke."
   :type 'string
-  :group 'browse-url
   :version "23.1")
 
 (defcustom browse-url-text-emacs-args (and (not window-system)
@@ -572,8 +553,7 @@ The default is none in a window system, otherwise `-show_cursor' to
 indicate the position of the current link in the absence of
 highlighting, assuming the normal default for showing the cursor."
   :type '(repeat (string :tag "Argument"))
-  :version "23.1"
-  :group 'browse-url)
+  :version "23.1")
 
 (defcustom browse-url-text-input-field 'avoid
   "Action on selecting an existing text browser buffer at an input field.
@@ -586,36 +566,30 @@ down (this *won't* always work)."
   :type '(choice (const :tag "Move to try to avoid field" :value avoid)
                  (const :tag "Disregard" :value nil)
                  (const :tag "Warn, don't emit URL" :value warn))
-  :version "23.1"
-  :group 'browse-url)
+  :version "23.1")
 
 (defcustom browse-url-text-input-attempts 10
   "How many times to try to move down from a series of text browser input fields."
   :type 'integer
-  :version "23.1"
-  :group 'browse-url)
+  :version "23.1")
 
 (defcustom browse-url-text-input-delay 0.2
   "Seconds to wait for a text browser between moves down from an input field."
   :type 'number
-  :version "23.1"
-  :group 'browse-url)
+  :version "23.1")
 
 (defcustom browse-url-kde-program "kfmclient"
   "The name by which to invoke the KDE web browser."
   :type 'string
-  :version "21.1"
-  :group 'browse-url)
+  :version "21.1")
 
 (defcustom browse-url-kde-args '("openURL")
   "A list of strings defining options for `browse-url-kde-program'."
-  :type '(repeat (string :tag "Argument"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Argument")))
 
 (defcustom browse-url-elinks-wrapper '("xterm" "-e")
   "Wrapper command prepended to the Elinks command-line."
-  :type '(repeat (string :tag "Wrapper"))
-  :group 'browse-url)
+  :type '(repeat (string :tag "Wrapper")))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; URL encoding
@@ -1673,6 +1647,58 @@ from `browse-url-elinks-wrapper'."
      (error "Unrecognized exit-code %d of process `elinks'"
             exit-status))))
 
+;;; Adding buttons to a buffer to call `browse-url' when you hit them.
+
+(defvar browse-url-button-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map "\r" 'browse-url-button-open)
+    (define-key map [mouse-2] 'browse-url-button-open)
+    (define-key map "w" 'browse-url-button-copy)
+    map)
+  "The keymap used for browse-url buttons.")
+
+(defface browse-url-button
+  '((t :inherit link))
+  "Face for browse-url buttons (i.e., links)."
+  :version "27.1")
+
+(defun browse-url-add-buttons ()
+  "Add clickable buttons to the text following point in the current buffer.
+Everything that matches `browse-url-button-regexp' will be made
+clickable and will use `browse-url' to open the URLs in question."
+  (let ((inhibit-read-only t))
+    (save-excursion
+      (while (re-search-forward browse-url-button-regexp nil t)
+        (add-text-properties (match-beginning 0)
+                             (match-end 0)
+                             `(help-echo "Open the URL under point"
+                                         keymap ,browse-url-button-map
+                                         face browse-url-button
+                                         button t
+                                         browse-url-data ,(match-string 0)))))))
+
+(defun browse-url-button-open (&optional external mouse-event)
+  "Follow the link under point using `browse-url'.
+If EXTERNAL (the prefix if used interactively), open with the
+external browser instead of the default one."
+  (interactive (list current-prefix-arg last-nonmenu-event))
+  (mouse-set-point mouse-event)
+  (let ((url (get-text-property (point) 'browse-url-data)))
+    (unless url
+      (error "No URL under point"))
+    (if external
+        (funcall browse-url-external-browser url)
+      (browse-url url))))
+
+(defun browse-url-button-copy ()
+  "Copy the URL under point"
+  (interactive)
+  (let ((url (get-text-property (point) 'browse-url-data)))
+    (unless url
+      (error "No URL under point"))
+    (kill-new url)
+    (message "Copied %s" url)))
+
 (provide 'browse-url)
 
 ;;; browse-url.el ends here