[racket] Key events, shift, and, get-shift-key-code

I believe that "other-shift-key-code" is really just a field with
getters and setters; there's no smarts in the key-event class that can
do the translation you want.

It may be possible to do this via calls directly to the os, but I'm
not sure how to do that and I've never had much luck reading the cocoa
docs, I'm sorry to say. It might help to look at the code inside
racket/gui that constructs the key-event; it's in the collection
mred/private/wx/cocoa.

hth,
Robby


On Wed, Dec 24, 2014 at 8:29 AM, Jens Axel Søgaard
<jensaxel at soegaard.net> wrote:
> Hi All,
>
> Om my keyboard the . key wil produce an > if i press shift and . at
> the same time.
> How can I write a program that given . can produce > ?
>
> I have experimented with the program below. It displays a canvas and
> prints info on the key events received. My experiments with get-other-shift-code
> has been unsuccessful. The documentation says that on OS X it works only
> of cmd is pressed, but I can't get it to return anything but #f.
>
> /Jens Axel
>
>
>
> #lang racket
> (require racket/gui)
>
> ; key-event->key : key-event -> string
> ;   translate a key event into a "Emacs" style string
> ; Pressed       Output
> ;   a             "a"
> ; Shift+a         "A"
> ; Meta+a        "M-a"
> ; Shift+Meta+a  "M-A"         ; <== todo returns "M-a" now
> (define (key-event->key event)
>   (define shift? (send event get-shift-down))
>   (define c      (send event get-key-code))
>   (define k      (if shift?
>                      (or (send event get-other-shift-key-code) c)
>                      c))
>   (define ctrl?  (send event get-control-down))
>   (define alt?   (send event get-alt-down))
>   (define meta?  (send event get-meta-down))
>   (let ([k (match k ['escape "ESC"] [_ k])])
>     (cond
>       [(or ctrl? alt? meta?) (~a (if ctrl? "C-" "")
>                                  (if alt?  "A-" "")
>                                  (if meta? "M-" "")
>                                  k)]
>       [else                  k])))
>
>
> ; key-event/no-modifiers : make a copy of key-event with no modifiers set
> (define (key-event/no-modifiers key-event)
>   (define e key-event)
>   (new key-event%
>        [key-code   (send e get-key-code)]
>        [shift-down   #f]
>        [control-down #f]
>        [meta-down    #f]
>        [alt-down     #f]
>        [x            (send e get-x)]
>        [y            (send e get-y)]
>        [time-stamp   (send e get-time-stamp)]
>        [caps-down    #f]
>        [mod3-down    #f]
>        [mod4-down    #f]
>        [mod5-down    #f]
>        [control+meta-is-altgr #f]))
>
> (define (get-shift-key-code key-event)
>   (define e (key-event/no-modifiers key-event))
>   (send e set-shift-down #t)
>   (send e get-other-shift-key-code))
>
>
> (define frame (new frame% [label "Display Key Event"]))
>
> (define msg (new message% [parent frame] [label "No news"]))
> (send msg min-width 400)
>
>
> (define key-canvas%
>   (class canvas%
>     (define/override (on-char event)
>       (define key (key-event->key event))
>       (unless (equal? key 'release)
>         (displayln (list 'key key 'shift (get-shift-key-code event)))
>         (send msg set-label (~a "key: " key "    " "shift: "
> (get-shift-key-code event)))))
>     (super-new)))
>
> (define canvas (new key-canvas% [parent frame]))
> (send canvas min-client-width  400)
> (send canvas min-client-height 400)
> (send msg set-label "Don't panic")
> (send frame show #t)
>
>
> --
> --
> Jens Axel Søgaard
>
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