Add gemini to browse-url-button-regexp

Also I overengineered some other stuff around that.

init.el

@@ -886,6 +886,9 @@ if ripgrep is installed, otherwise `consult-grep'."
            (elpher-go url))
           (t (apply fn url args))))
 
+  ;; And buttonize gemini:// links.
+  (acdw/add-button-url-regexp-protocol "gemini")
+
   (:when-loaded
    (setup (:straight (gemini-write
                       :host nil

lisp/acdw.el

@@ -407,6 +407,75 @@ Prompt only if there are unsaved changes."
   (custom-set-faces '(fringe
                       ((t (:foreground "dim gray"))))))
 
+
+;;; URL regexp
+;; really, I just want to add gemini:// protocol, but I'm going to do some
+;; reverse-engineering here.
+
+(defvar acdw/button-protocols '("http"
+                                "https"
+                                "shttp"
+                                "shttps"
+                                "ftp"
+                                "file"
+                                "gopher"
+                                "nntp"
+                                "news"
+                                "telnet"
+                                "wais"
+                                "mailto"
+                                "info")
+  "The list of protocols to splice into `browse-url-button-regexp'.")
+
+(defun acdw/build-button-url-regexp ()
+  "Build `browse-url-button-regexp' from `acdw/button-protocols'.
+I used `xr' (not included in Emacs) to get the RX form of the
+default, so I can easily splice the list into it.  THIS IS
+BRITTLE AF!!!"
+  (rx
+   (seq word-boundary
+        (group
+         (group
+          (or "www."
+              (seq
+               (group
+                (eval (cons 'or acdw/button-protocols)))
+               ":")))
+         (opt
+          (group "//"
+                 (one-or-more
+                  (any "0-9a-z" "._-"))
+                 ":"
+                 (zero-or-more
+                  (any "0-9"))))
+         (or
+          (seq
+           (one-or-more
+            (any "0-9a-z" "!#$%&*+,./:;=?@\\_~-" word))
+           "("
+           (one-or-more
+            (any "0-9a-z" "!#$%&*+,./:;=?@\\_~-" word))
+           (zero-or-more
+            (any "0-9a-z" "#$%&*+/=@\\_~-" word))
+           ")"
+           (opt
+            (one-or-more
+             (any "0-9a-z" "!#$%&*+,./:;=?@\\_~-" word))
+            (any "0-9a-z" "#$%&*+/=@\\_~-" word)))
+          (seq
+           (one-or-more
+            (any "0-9a-z" "!#$%&*+,./:;=?@\\_~-" word))
+           (any "0-9a-z" "#$%&*+/=@\\_~-" word))))))
+  )
+
+(defun acdw/add-button-url-regexp-protocol (proto)
+  "Add PROTO to `browse-url-button-regexp'
+First, add PROTO to `acdw/button-protocols'.
+Then, build `browse-url-button-regexp' with the new protocol."
+  (add-to-list 'acdw/button-protocols proto)
+  (setq browse-url-button-regexp (acdw/build-button-url-regexp)))
+
+
 
 ;;; Keymaps