CODEWITHSUNDEEP
common-lispltk
Lissomort
Lissomort

Reputation: 103

LTK, button action

My first LTK-application. Trying to execute function with argument from entry-field.

(defpackage :test
  (:use :cl
    :ltk))

(in-package :test)

(defun main()
  (with-ltk ()
    (let* ((f (make-instance 'frame
                 :height 200
                 :width 300))
       (e (make-instance 'entry
                 :master f
                 ))
       (b (make-instance 'button
                 :master f
                 :text "Go"
                 :command (test (text e)))))
      (wm-title *tk* "Test")
      (pack f)
      (pack e :side :left)
      (pack b :side :left)
      (configure f :borderwidth 3)
      (configure f :relief :sunken))))

(defun test (str)
  (format t "String: ~a" str))

Why function execute just once, when source is launched? And then - any actions.

Upvotes: 3

Views: 662

Answers (1)

Vsevolod Dyomkin
Vsevolod Dyomkin

Reputation: 9451

If you want to pass a callback, use (lambda () ...), i.e. in your code:

...
(b (make-instance 'button
                  :master f
                  :text "Go"
                  :command (lambda () (test (text e))))))

Otherwise, your (test (text e)) is executed at the time of make-instance call, before the object is initialized.

It's easier to spot this problems, if you turn on debug output: (setf ltk:*debug-tk* t)

Upvotes: 3

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