add-text-properties -vs- set-extent-property (XEmacs)

add-text-properties -vs- set-extent-property (XEmacs)

[Steven L. Baur]

The compatibility problem is this, when XEmacs puts properties on text
the properties get propagated when text is inserted at the front.
This causes various kinds of wierdness in gnus-topic (my patch of
yesterday will still break due to this), and also pseudo articles in
the *Summary* buffer (off the top of my head).

Here is a short illustration:

;;; This example follows existing Gnus practice
;;; Both strings get inserted with properties attached to the first string
(defun test-text-properties ()
  (interactive)
  (let ((beg (point)))
    (save-excursion
      (insert "This is a test.\n")
      (add-text-properties beg (point) (list 'start-open t
					     'face 'italic
					     'start-closed nil
					     'steve-property "Emacs Rules"))))
  (insert "This is some more text.\n"))

;;; This example is non-portable to GNU Emacs, but works
(defun test-text-properties-2 ()
  (interactive)
  (let ((beg (point))
	extent)
    (save-excursion
      (insert "This is a test.\n")
      (setq extent (make-extent beg (point)))

      (set-extent-property extent 'start-open t)
      (set-extent-property extent 'steve-property "Emacs Rules!")
      (set-extent-property extent 'face 'italic)))
  (insert "This is some more text, should be excluded from previous.\n"))

-- 
steve@miranova.com baur