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Re: basic view-key-event-handler confusion
- To: firstname.lastname@example.org (Tom McDougal)
- Subject: Re: basic view-key-event-handler confusion
- From: email@example.com (Bill St. Clair)
- Date: Wed, 18 Nov 1992 12:03:59 -0600
- Cc: info-mcl
>There is something *very basic* that I don't understand about
>view-key-event-handlers, despite having read and re-read
>the docs and sample code a hundred times. Here is a simple
>example that fails to handle key events -- all keystrokes go
>to the listener:
>(defclass simple-key-handling-view (dialog-item)
>;;; When you get a keystroke, draw that character.
>;;; ***BUT NOTHING HAPPENS
>(defmethod view-key-event-handler ((item simple-key-handling-view)
> "Just print the character in the view."
> (when (integerp char) (setq char (code-char char))) ; (why?)
> (move-to item 20 20)
> (format item "~c" char))
>(setq *w* (make-instance 'window))
>(setq *v* (make-instance 'simple-key-handling-view
> :view-position #@(4 4)
> :view-size #@(200 200)))
>(add-subviews *w* *v*)
>;;; (key-handler-p *v*) --> NIL
>Please don't tell me to use an instance of some text dialog
>item; I want to do something very special with the keystrokes,
>and anyway there must be a simpler way...
>Many, many thanks for your kind attention.
The problem is that the window is not passing the VIEW-KEY-EVENT-HANDLER
call on to your dialog item. If you mix in the KEY-HANDLER-MIXIN class, this
will be done for you. It also makes KEY-HANDLER-P return true.
(defclass simple-key-handling-view (key-handler-mixin dialog-item)
It looks a little better if you erase before drawing. Also, the CHAR arg
to view-key-event-handler is a character. No need to coerce it from an
(defmethod view-key-event-handler ((item simple-key-handling-view) char)
"Just print the character in the view."
; (when (integerp char) (setq char (code-char char))) ; (why?)
(with-focused-view (view-container item)
(rlet ((rect :rect :topleft #@(0 0) :botright #@(100 100)))
(move-to item 20 20)
(format item "~c" char))