CODEWITHSUNDEEP
emacselisp
sailing
sailing

Reputation: 455

How do I get the region (selection) programmatically in Emacs Lisp?

I need to access the selection in Emacs buffer. I have found this article How do I access the contents of the current region in Emacs Lisp? and it helps me a lot.

But there is a problem. The first time I select (highlight) a region, it works okay, but when I press C-g, and move cursor normally to another place without highlighting any chars, I got a string from last mark to the current point while I expect an empty one.

Actually I need to implement a function which will return the current selection (highlighted) as a string, or empty string if nothing is highlighted. The following code may express me more clearly.


(defun get-search-term ()
  (interactive)
  (let (
        (selection (buffer-substring-no-properties (region-beginning) (region-end))))
    (if (= (length selection) 0)
        (message "empty string")
      (message selection))))

Any suggestions? Thanks a lot!

Upvotes: 24

Views: 8751

Answers (2)

event_jr
event_jr

Reputation: 17707

"r" specification of interactive is dumb. You're seeing why.

(defun get-search-term (beg end)
  "message region or \"empty string\" if none highlighted"
  (interactive (if (use-region-p)
                   (list (region-beginning) (region-end))
                 (list (point-min) (point-min))))
  (let ((selection (buffer-substring-no-properties beg end)))
    (if (= (length selection) 0)
        (message "empty string")
      (message selection))))

I don't mean "dumb" as in stupid and not useful; just that it doesn't care about whether the mark is active or not. I think it predates transient-mark-mode.

EDIT: Using (point-min) twice above makes the code harder to understand when re-reading. Here is a better implementation:

(defun get-search-term (beg end)
  "message region or \"empty string\" if none highlighted"
  (interactive (if (use-region-p)
                   (list (region-beginning) (region-end))
                 (list nil nil)))
  (message "%s" (if (and beg end)
                    (buffer-substring-no-properties beg end)
                  "empty string")))

Upvotes: 32

cwsw
cwsw

Reputation: 19

Check variable mark-active eg. C-h v mark-active

==> mark-active is a variable defined in `C source code'. Its value is nil Local in buffer Apropos; global value is nil

Automatically becomes buffer-local when set in any fashion.

Documentation: Non-nil means the mark and region are currently active in this buffer.

(defun get-search-term ()
  (interactive)
  (if mark-active
      (let (
        (selection (buffer-substring-no-properties (region-beginning) (region-end))))
    (if (= (length selection) 0)
        (message "empty string")
      (message selection))
    )
    (error "mark not active"))
  )

Upvotes: 1

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