如何在瞬态标记模式下使elisp中的区域瞬态

Question

I wrote an elisp macro that preserves the region when in transient-mark-mode :

(defmacro keep-region (command)
  "Wrap command in code that saves and restores the region"
  (letrec ((command-name (symbol-name command))
           (advice-name (concat command-name "-keep-region")))
    `(progn
       (defadvice ,command (around ,(intern advice-name))
         (let (deactivate-mark)
           (save-excursion
             ad-do-it)))
       (ad-activate (quote ,command)))))

(keep-region replace-string)
(keep-region replace-regexp)

This preserves the region for commands that are advised using the keep-region macro; very helpful when you want to make multiple replacements in a selected block.

The problem is that after running a command that has been advised using this macro, the region loses its transient nature; subsequent movement commands extend the region, rather than deselecting it.

How can I programmatically re-enable the transience of the marked region?

Answer 1

From Ch f transient-mark-mode :

Transient Mark mode is a global minor mode. When enabled, the region is highlighted whenever the mark is active . The mark is "deactivated" by changing the buffer, and after certain other operations that set the mark but whose main purpose is something else--for example, incremental search, <, and >.

Hence, activate-mark after exchange-point-and-mark should restore the transient nature of the mark.

I am not sure, though, why you are using exchange-point-and-mark here, and why you are calling it twice. In my opinion, just saving (point) and (mark) in a let -binding and restoring them after ad-do-it would be easier. push-mark and pop-mark might help as well, since the latter automatically reactivates the mark anyway.

Answer 2

Just remove your calls to exchange-point-and-mark . The preservation is done by the deactive-mark let-binding anyway.

Answer 3

The problem is that after running a command that has been advised using this macro, the region loses its transient nature; subsequent movement commands extend the region, rather than deselecting it.

You should rather talk about "shift-selected nature": movement commands extending the region is what happens when the mark is activated in the "normal" way.

The shift-select status is stored inside the transient-mark-mode variable, and is modified by someone ( handle-shift-selection ?) who doesn't care about the value of deactivate-mark . We can get around this by saving the value of transient-mark-mode :

(defmacro keep-region (command)
  "Wrap command in code that saves and restores the region"
  (letrec ((command-name (symbol-name command))
           (advice-name (concat command-name "-keep-region")))
    `(progn
       (defadvice ,command (around ,(intern advice-name))
         (let ((deactivate-mark nil)
               (transient-mark-mode transient-mark-mode))
           (save-excursion
             ad-do-it)))
       (ad-activate (quote ,command)))))

---

transient-mark-mode is a variable defined in `buffer.c'.

...

Lisp programs may give this variable certain special values:

...

• A value of (only . OLDVAL) enables Transient Mark mode temporarily. After any subsequent point motion command that is not shift-translated, or any other action that would normally deactivate the mark (eg buffer modification), the value of
  `transient-mark-mode' is set to OLDVAL.