[racket-dev] get-x method on key event always returns zero?

On Oct 9, 2013, at 7:40 PM, Matthias Felleisen wrote:

> 
> 
> world uses get-x like this: 
> 
>      (define/public (deal-with-mouse %)
>        (if (not on-mouse) 
>            ;; No mouse handler => discard mouse events (so snip are not selected
>            ;;  in the pasteboard, for example
>            (class %
>              (super-new)
>              (define/override (on-event e)
>                (void)))
>            ;; Mouse handler => handle mouse events
>            (class %
>              (super-new)
>              (define/override (on-event e)
>                (define-values (x y me) (mouse-event->parts e))
>                (when live
>                  (cond
>                    [(and (<= 0 x width) (<= 0 y height)) (pmouse x y me)]
>                    [(member me '("leave" "enter")) (pmouse x y me)]
>                    [else (void)]))))))
> 
> [[ Yes, this is a method-based mixin ]]
> 
> but note that I override on-event not on-key. The mouse-event->parts method uses get-x on e. -- Matthias

Right... I was hoping to use get-x on a key event. The docs suggest that it should work. Obviously, the workaround is just to capture the x value whenever the mouse moves.  Maybe get-x should just be removed from the key event?

John

> 
> 
> 
> On Oct 9, 2013, at 5:17 PM, John Clements wrote:
> 
>> It appears to me that the 'get-x' method on a key event always returns zero, counter to what the docs say. Is this a doc bug, a software bug, or just me being dumb?
>> 
>> FWIW, here's a simple program that illustrates this; press a key while the window has focus, and you will always see 0 in the x value field:
>> 
>> #lang racket/base
>> 
>> 
>> (require racket/gui
>>        racket/class)
>> 
>> 
>> (define sound-canvas%
>> (class canvas%
>>   (init-field frame-num-text)
>>   (init-field y-value-text)
>> 
>>   (define/override (on-char evt)
>>     (send y-value-text begin-edit-sequence #f)
>>     (send y-value-text erase)
>>     (send y-value-text insert 
>>           (format "x value: ~v"
>>                   (send evt get-x)))
>>     (send y-value-text end-edit-sequence)
>>     (send frame-num-text begin-edit-sequence #f)
>>     (send frame-num-text erase)
>>     (send frame-num-text insert (format "key : ~a" (send evt get-key-code)))
>>     (send frame-num-text end-edit-sequence))
>> 
>>   (super-new)))
>> 
>> 
>> (let* ([f (new frame% [label "abc"] [width 400] [height 100])]
>>      [tx (new text%)]
>>      [ty (new text%)]
>>      [c (new sound-canvas%
>>              [parent f]
>>              #;[paint-callback 
>>                 (make-sound-drawing-callback left-getter right-getter
>>                                              len data-left data-right)]
>>              [frame-num-text tx]
>>              [y-value-text   ty])]
>>      [ecx (new editor-canvas%
>>                [parent f]
>>                [editor tx]
>>                [style '(no-border no-hscroll no-vscroll)]
>>                [stretchable-width #t]
>>                [stretchable-height #f]
>>                [horizontal-inset 1]
>>                [vertical-inset 1]
>>                [min-width 50]
>>                [min-height 20])]
>>      [ecy (new editor-canvas%
>>                [parent f]
>>                [editor ty]
>>                [style '(no-border no-hscroll no-vscroll)]
>>                [stretchable-width #t]
>>                [stretchable-height #f]
>>                [horizontal-inset 1]
>>                [vertical-inset 1]
>>                [min-width 50]
>>                [min-height 20])])
>> (send f show #t))
>> 
>> 
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>