How to distinguish character from noncharacter input events?

How to distinguish character from noncharacter input events?

[Joe Fineman]

Is there a function that distinguishes character from noncharacter
input events?  It would be nice to be able to write

(let ((next (read-event)))
  (if (char-p next)
      (progn ...)
    (...)))

but I can't find anything of the sort.
-- 
---  Joe Fineman    jcf@TheWorld.com

||:  Money is especially valuable in that it is overvalued.  :||

Re: How to distinguish character from noncharacter input events?

[Stefan Monnier]

> Is there a function that distinguishes character from noncharacter
> input events?  It would be nice to be able to write

> (let ((next (read-event)))
>   (if (char-p next)
>       (progn ...)
>     (...)))

> but I can't find anything of the sort.

What for?
What's your definition of a "character event"?

You could try

   (integerp event)

but it will also return non-nil for M-p and C-x.  So you might want to use

   (and (integerp event) (null (event-modifiers event))

but it all depends on what you consider to be a character event, of course.


        Stefan

Re: How to distinguish character from noncharacter input events?

[Joe Fineman]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> What's your definition of a "character event"?

As a practical matter, it means an event that will not give the error
message "non-character input event" when read-char encounters it.

> You could try

Thank you for the hints.
-- 
---  Joe Fineman    jcf@TheWorld.com

||:  Bless you, you will be blameless yet,  :||
||:  For God forgives, and men forget.      :||

Re: How to distinguish character from noncharacter input events?

[Kevin Rodgers]

Joe Fineman wrote:
 > Stefan Monnier <monnier@iro.umontreal.ca> writes:
 >>What's your definition of a "character event"?
 >
 > As a practical matter, it means an event that will not give the error
 > message "non-character input event" when read-char encounters it.

You could implement the same check as read-char:

(defun character-event-p (event)
   "Return non-nil if EVENT is a character event."
   ;; see Fread_char:
   (if (symbolp event)
       (let* ((mask (get event 'event-symbol-element-mask))
              (char (if mask
                        (get (car mask) 'ascii-character))))
         (if char
             (setq event (logior char (car (cdr mask)))))))
   (integerp event))

-- 
Kevin Rodgers

Re: How to distinguish character from noncharacter input events?

[Kai Grossjohann]

Joe Fineman <jcf@TheWorld.com> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>> What's your definition of a "character event"?
>
> As a practical matter, it means an event that will not give the error
> message "non-character input event" when read-char encounters it.

Use condition-case, call read-char and catch the error.  That will
tell you whether read-char gives the error message.

Kai

Re: How to distinguish character from noncharacter input events?

[Joakim Hove]

Joe Fineman <jcf@TheWorld.com> writes:

> Is there a function that distinguishes character from noncharacter
> input events?  It would be nice to be able to write
>
> (let ((next (read-event)))
>   (if (char-p next)
>       (progn ...)
>     (...)))
>

Assuming that by 'character input event' you mean keypresses which
just lead to immediate insertion of the corresponding character, you
might be able to make use of the function (self-insert-command N),
which is run everytime you insert characters in the buffer.

Joakim


-- 
Joakim Hove
hove AT ift uib no
+47 (55 5)8 27 90
http://www.ift.uib.no/~hove/

Re: How to distinguish character from noncharacter input events?

[Ehud Karni]

On Wed, 11 Aug 2004 05:25:15 +0200, Joakim Hove <hove@ift.uib.no> wrote:
>
> Joe Fineman <jcf@TheWorld.com> writes:
>
> > Is there a function that distinguishes character from noncharacter
> > input events?  It would be nice to be able to write
> >
> > (let ((next (read-event)))
> >   (if (char-p next)
> >       (progn ...)
> >     (...)))

You can use other predicates to distinguish, something like this:

(defun test-event ()
  (interactive)
  (let ((next (read-event "Enter event")))
  ;;   (describe-variable 'next)           ;; for debug
       (if (listp next)
           (message "Real event (mouse)")
           (if (numberp next)
               (message "Real char read")
               (message "Key press (non char) read")))))

Ehud.


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