Detecting keyboard state / finding older fixes

Herbert König wrote

Hello Stan,

I forgot:

sff>> operating system. I'd like to check the real position of a key, up or down, so I
sff>> can ignore the repeats. I can't find any way to do this.

HK> Keyboard event understands #isKeyDown and #isKeyUp.

and don't forget to check the event's timestamp. Never did this myself
but you can not rely on the fact that you will receive keyDown before
keyUp.



Cheers

Herbert                            mailto:herbertkoenig@gmx.net

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Bert Freudenberg wrote

On Mar 4, 2008, at 19:19 , stan shepherd wrote:

> handleKeyUp: anEvent
> Transcript show: ' evt is down ',anEvent isKeyDown asString; cr.
>         "now press and hold a key"
>
> shows
>
>  evt is down false

Which is of course expected since only keyUp events are passed into  
#handleKeyUp:, so #isKeyDown always is false.

You need to handle both keyDown and keyUp events, and track the state  
of pressed keys.

Note that the keyValue in up/down events is system-specific (unlike  
keyStroke events which have actual characters).

Also note that this behavior also depends on your OS and VM version.  
The Windows VM handles up/down events nicely for a long time, Mac VMs  
since recently, Unix VMs are broken I think.

I'm attaching a small example morph demonstrating this.

- Bert -


 
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Bert Freudenberg wrote

Assuming this is for a game, you would effectively prevent someone  
"hammering" on a key to do some action repeatedly. Also this depends  
on the actual repeat rate which varies widely between systems. In my  
example there is no such fixed timeout, you simply would check if the  
key is pressed already (i.e. it is in the keys set).

- Bert -

Bert Freudenberg wrote

On Mar 7, 2008, at 14:54 , stan shepherd wrote:

>
> Where I was confused is that checking if the key is pressed already  
> doesn't
> appear to differentiate between a 'real' key down and a repeat. For  
> example
> :
>
> keyDown: anEvent
> (keys includes: anEvent keyValue)
> ifTrue: [Transcript show: 'skipped ' , anEvent asString; cr]
> ifFalse: [keys add: anEvent keyValue. "
> Transcript show: 'key down ' , anEvent asString; cr.
> self changed]
>
> always takes the 'key down' branch, even for key held down.
>
> Was this what you meant?

Yes. The code above works as expected on Mac OS X, printing  
"skipped..." for auto-repeats.


> On the other hand, looping over this in a thread:
>
> keyStrokes
> keys
> do: [:key | key
> ifNotNil: [(oldKeys includes: key)
> ifFalse: [Transcript show: 'key added ' , key asString;
> cr]]].
> oldKeys do: [:key | key
> ifNotNil: [(keys includes: key)
> ifFalse: [Transcript show: 'key removed ' , key asString;
> cr]]].
> oldKeys := keys copy.
>
> has the desired effect of only showing real key moves.
>
> Is this over complicating things?

It indeed sounds overly complicated, unless your platform forces you  
to resort to such things. Are you on Linux by chance?

- Bert -
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Bert Freudenberg wrote

I am pretty sure it works in the Windows VM. You should get multiple  
keyDown events but a single keyUp:

Down ... (pause) ... down - down - down - down - down - up.

> That is, in the programming language a real key down and a repeat are
> indistinguishable.

The problem is that from the X11 VM you get this:

Down ... (pause) ... up down - up down - up down - up down - up.

Now, the up and down events bear the same time stamp (they are  
synthesized together) so the VM could actually filter out the  
unwanted up events, but it does not (yet anyway). Also, you do not  
get events for all keys like Shift etc. (IIRC only Windows gets that  
right).

It's a shame to admit this is still not working ...

- Bert -