[Vm-dev] Multiple Keydown and up

David T. Lewis lewis at mail.msen.com
Wed Jan 6 21:27:45 UTC 2021


On Tue, Jan 05, 2021 at 09:22:58PM -0800, tim Rowledge wrote:
>  
> 
> 
> > On 2021-01-05, at 6:54 PM, Yoshiki Ohshima <Yoshiki.Ohshima at acm.org> wrote:
> > 
> > Hi,
> > 
> > Another  Raspberry Pi  Scratch issue report but possibly affects Squeak on other platforms.
> > 
> > A user reported that if you press down one key, and then another key, and then try to release both keys, the key up for the first key does not get reported.
> > 
> > https://youtu.be/N9q8DxYWAik
> > 
> > It could be the way Scratch handles them, but maybe it is an VM issue. Can somebody give me insight?\
> 
> It depends; is this the NuScratch as delivered in Raspbian? Or the package loaded into a post 5.1 image?
> 
> In experiments updating to a 5.3 image I notice that the  keyboard listener
> I wroet way back when no longer seems to work as well. I do recall Marcel
> doing work in that general area and changing how events are dealt with;
> I'm guessing it will be related.
> 
> Scratch expects to see a state for each key, rather than handle events - in
> *some* places. Sigh. Anything that makes the KeyboardStateWatcher class not
> accurately track the key events will mess up some things. Or indeed, if I
> made any mistakes or failed to catch every possible case, which must be
> possible.
> 

I'm sorry I cannot provide a reference, but I think that I recall some
discussion of this in earlier years. It may be that this was caused by
a limitation related to X11 key event delivery in the Unix VM. Possibly
there is some discussion in the vm-dev archives. That's all I remember
and it might be wrong.

Dave



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