[PATCH 2/2] Allow grabbing clients to accept or reject touches any time

Chase Douglas chase.douglas at canonical.com
Wed Sep 14 12:20:10 PDT 2011

On 09/14/2011 02:04 PM, Peter Hutterer wrote:
> On Wed, Sep 14, 2011 at 12:09:02PM -0500, Chase Douglas wrote:
>> On 09/14/2011 11:59 AM, Peter Hutterer wrote:
>>> On Wed, Sep 14, 2011 at 10:22:36AM -0500, Chase Douglas wrote:
>>>> This is potentially both a performance and client complexity
>>>> improvement.
>>> this needs more description, especially for the archives (we just talked
>>> about this here at the XDC), please add that to the commit message.
>>> and one more thing: if a client can reject a sequence at any time it may be
>>> that the sequence already disappeared by the time the reject is processed.
>>> (this shouldn't happen unless the client buffers the request but thats been
>>> known to happen).
>>> should we allow clients to reject any touch (even invalid ones) without
>>> returning a BadValue?
>> Hmmm... The same could happen with accept too:
>> * Client A owns touch
>> * Client B has a touch grab and is listening too
>> 1. Client A accepts touch
>> 2. TouchEnd sent to client B
>> 3. Client B accepts touch (which means, I accept iff I become the owner)
>> 4. TouchEnd reaches client B
>> 5. Client B gets an error from the touch acceptance because at the time
>> the server got the accept request, the touch has already ended for client B
>> We probably need to think a bit more about this...
> accept is a different case where the client should handle errors
> appropriately. reject is more fire-and-forget. same with Ungrab, iirc it
> always succeeds even if you don't actually have the grab.

This makes sense to me after further thought. I agree we should not emit
an error on reject if the touch id is invalid, as you suggest.

I'll send a v2 with this change and a more verbose commit message.

-- Chase

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