[cgreek:00012] Re: Rough implementation of works-list utilities

[Kenichi Handa <handa@xxxxxxxxx>]

TAKAHASHI Naoto <ntakahas@xxxxxxxxx> writes:
> The hook post-command-hook is executed after each command is executed.
> You could register a function to display the text properties under
> cursor in the modeline, but Handa-san told me that there is a better
> hook for such a purpose.  The name, however, escapes me.  What was
> that?

They are point-entered and point-left text properties.
Here's a simple example program.  After you load it, please
try:

(1) C-x b temp RET		-- to switch to temporary buffer "temp"
(2) M-x modify-mode-line RET	-- setup new mode-line-format
(3) M-x temp RET		-- insert sample lines

Then, when you move cursor, the mode-line shows the `tag'
property of a text under the cursor.   If there's no `tag'
property, "no tag" is shown.

However, currently, alpha version of Emacs 21 has a bug.
C-f doesn't update mode-line properly if C-f doesn't change
a line for a while, i.e, the mode-line is udpated 3 seconds
later.

---
Ken'ichi HANDA
handa@xxxxxxxxx

(defvar mode-line-tag nil)

(defun show-tag (old new)
  (setq mode-line-tag (get-text-property new 'tag))
  (force-mode-line-update))

(defun hide-tag (old new) 
  (setq mode-line-tag nil)
  (force-mode-line-update))

(defun modify-mode-line ()
  (interactive)
  (setq mode-line-format (copy-sequence mode-line-format))
  (let ((slot (or (memq 'mode-line-buffer-identification mode-line-format)
		  (memq 'mode-line-modified mode-line-format))))
    (if slot
	(setcdr slot
		(cons '(mode-line-tag mode-line-tag "no tag") (cdr slot))))))

(defun temp ()
  (interactive)
  (let ((str1 "the first line")
	(str2 "the second line"))
    (add-text-properties 0 (length str1)
			 '(tag "tag1"
			       point-entered show-tag
			       point-left hide-tag)
			 str1)
    (add-text-properties 0 (length str2)
			 '(tag "tag2"
			       point-entered show-tag
			       point-left hide-tag)
			 str2)
    (insert str1 "\n" str2 "\n")))