activate-mark-hook

[Chong Yidong]

Two issues:

1. activate-mark-hook and deactivate-mark-hook do not have docstrings,
even though they are documented in the Emacs Lisp reference manual (Elisp
-> Markers -> The Mark).

2. If push-mark-command is run with no prefix arg and mark already set at
the current position, it activates the mark, but fails to run
activate-mark-hook. I noticed this because I have the following in my
`.emacs':

  (transient-mark-mode t)
  (add-hook 'deactivate-mark-hook '(lambda () (setq cursor-type t)))
  (add-hook 'activate-mark-hook '(lambda () (setq cursor-type 'bar)))

If I type C-SPC C-g C-SPC, the hook is not run on the second invocation of
C-g, and the cursor doesn't change.

Here is a patch:

*** emacs/lisp/simple.el~       Thu Mar  3 14:59:58 2005
--- emacs/lisp/simple.el        Thu Mar  3 15:45:42 2005
***************
*** 2875,2880 ****
--- 2875,2888 ----
  (put 'mark-inactive 'error-conditions '(mark-inactive error))
  (put 'mark-inactive 'error-message "The mark is not active now")

+ (defvar activate-mark-hook nil
+   "Hook run when the mark becomes active.
+ It is also run at the end of a command, if the mark is active and
+ it is possible that the region may have changed")
+
+ (defvar deactivate-mark-hook nil
+   "Hook run when the mark becomes inactive.")
+
  (defun mark (&optional force)
    "Return this buffer's mark value as integer; error if mark inactive.
  If optional argument FORCE is non-nil, access the mark value
***************
*** 2966,2971 ****
--- 2974,2980 ----
      (if (or arg (null mark) (/= mark (point)))
        (push-mark nil nomsg t)
        (setq mark-active t)
+       (run-hooks 'activate-mark-hook)
        (unless nomsg
        (message "Mark activated")))))