+(defun elpher-gemini-pref-expand-collapse (button)
+ "Function called when the preformatted text toggle BUTTON is activated."
+ (let ((id (button-get button 'pref-id)))
+ (if (invisible-p id)
+ (remove-from-invisibility-spec id)
+ (add-to-invisibility-spec id))
+ (redraw-display)))
+
+(defun elpher-gemini-insert-preformatted-toggler (alt-text)
+ "Insert a button for toggling the visibility of preformatted text.
+If non-nil, ALT-TEXT is displayed alongside the button."
+ (let* ((url-string (url-recreate-url (elpher-page-address elpher-current-page)))
+ (pref-id (intern (concat "pref-"
+ (number-to-string (point))
+ "-"
+ url-string))))
+ (insert elpher-gemini-preformatted-toggle-bullet)
+ (when alt-text
+ (insert (propertize (concat alt-text " ")
+ 'face 'elpher-gemin-preformatted)))
+ (insert-text-button elpher-gemini-preformatted-toggle-label
+ 'action #'elpher-gemini-pref-expand-collapse
+ 'pref-id pref-id
+ 'face 'elpher-gemini-preformatted-toggle)
+ (add-to-invisibility-spec pref-id)
+ (newline)
+ pref-id))
+
+(defun elpher-gemini-insert-preformatted-line (line &optional pref-id)
+ "Insert a LINE of preformatted text.
+PREF-ID is the value assigned to the \"invisible\" text attribute, which
+can be used to toggle the display of the preformatted text."
+ (insert (propertize (concat (elpher-process-text-for-display line) "\n")
+ 'invisible pref-id
+ 'rear-nonsticky t)))
+