How to pass a variable to a click handler?

Question

I'm using this code to make clickable text in a buffer:

(defun q()
  "Entry point."
  (interactive)
  (let ((buffer-name "q"))
    (get-buffer-create buffer-name)
    (switch-to-buffer buffer-name)
    (with-current-buffer buffer-name
      (q-draw "foo"))))
(defun q-draw(my-var)
  "Draw MY-VAR on click."
  (let ((map (make-sparse-keymap)))
    (define-key map [mouse-1] 'q-handle-click)
    (insert (propertize "[Click]" 'keymap map 'mouse-face 'highlight 'help-echo "Click") "  ")))

But I'd like to pass a variable to my q-handle-click function. Is this possible?

(defun q-handle-click (my-var)
  "Insert MY-VAR."
  (interactive)
  (insert (format "%s" my-var)))

I can't find an example of the proper syntax, something like this doesn't work:

(define-key map [mouse-1] '(q-handle-click my-var))

Neither does this suggestion:

(define-key map [mouse-1] `(q-handle-click ,my-var))

Is a global variable my only option?

Does this answer your question? How to evaluate the variables before adding them to a list? — Drew, Apr 10 '22 at 16:51
It appears my mouse click handler is no longer called when I use this code. — gdonald, Apr 10 '22 at 18:23
Maybe I should have written this instead - just get rid of the quote: (define-key map [mouse-1] (q-handle-click my-var)). Presumably q-handle-click is a function that calculates the command to bind, taking (in this case) my-var as argument. Try that, to see. If that's the case then this question is instead a duplicate of another that asks about quote. — Drew, Apr 10 '22 at 23:27

score 1 · Accepted Answer · answered Apr 11 '22 at 00:07

You should bind the event to a command which calls your function with its argument.

(defun q-draw (my-var)
  "Draw MY-VAR on click."
  (let ((map (make-sparse-keymap)))
    (define-key map [mouse-1] (lambda () (interactive) (q-handle-click my-var)))
    (insert (propertize "[Click]" 'keymap map 'mouse-face 'highlight 'help-echo "Click") "  ")))

Or if you're not using lexical-binding in your library then you could use this approach:

(define-key map [mouse-1] `(lambda () (interactive) (q-handle-click ,my-var)))

How to pass a variable to a click handler?

1 Answers1