Re: [Xen-devel] [Qemu-devel] [PATCH] vnc: add additional key up event before repeated key down

[Peter Maydell <peter.maydell@xxxxxxxxxx>]

On 17 September 2014 04:24, Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote:
>> Which brings us to the other half of this: what does our
>> UI layer specify should be the behaviour for key repeat?
>> Gerd, can you clarify what the common input layer's expectation
>> is here? Should UI front ends call qemu_input_event_send_key()
>> with 'down/down/down/up' or 'down/up/down/up' semantics?
>
> It isn't formally specified anywhere.  The UIs usually simply pass
> through the key events they get.  IMO it is more useful to go for
> down/down/down/up.  This is how PS/2 works, and this allows the guest to
> figure whenever it's autorepeat or really multiple key presses.

Makes sense. It would be nice to have a comment somewhere
(include file near the prototype for the 'deliver key event'
function?) saying this is the required key-repeat behaviour.

I wouldn't be totally surprised if some of our UIs weren't
getting this right, but I'm not sure I care enough to audit
them all :-)

Anyway, I think this reinforces Markus's conclusion that
TigerVNC is correct and our VNC server implementation is
correct and the bug is in whichever PV guest is not
handling the key-repeat info it gets out of PS/2. (At least
I assume that the Xen config in question is going to send
key events via emulated PS/2; if it's something else I
guess that something else could potentially be buggy.)

-- PMM

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