[PATCH inputproto multitouch] Touch IDs must be at least unique per master device

Peter Hutterer peter.hutterer at who-t.net
Sat Dec 10 19:04:58 PST 2011

On Fri, Dec 09, 2011 at 01:43:44PM -0800, Chase Douglas wrote:
> From: Chase Douglas <cndougla at cndougla.(none)>
> XIAllowEvents with a master device and a touch ID must uniquely identify
> a touch sequence. If touch IDs were unique per slave device, multiple
> slave devices could have valid sequences with the same touch ID, and the
> sequences may both be grabbed through the same master device grab.
> Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
> ---
>  specs/XI2proto.txt |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> diff --git a/specs/XI2proto.txt b/specs/XI2proto.txt
> index c467bb1..d7b733b 100644
> --- a/specs/XI2proto.txt
> +++ b/specs/XI2proto.txt
> @@ -2151,7 +2151,7 @@ Touch tracking IDs are provided in the detail field of touch events. Its
>  value is always provided in every touch event. Tracking IDs are
>  represented as unsigned 32-bit values and increase in value for each new
>  touch, wrapping back to 0 upon reaching the numerical limit of IDs. IDs are
> -unique per each slave touch device.
> +unique per each master device.

how about "unique per device". that effectively (in the implementation)
means unique for the master but there's nothing particularly wrong with
having two SDs use the same ID if it's wrapped correctly (no, we won't write
the code for that, it's easier with server-wide IDs)

also, we should add a note that IDs are not guaranteed to be sequentially,
touch IDs may skip ahead by a few. clients _should_ know that implicitly
but better to spell it out


>  Touch events do not generate enter/leave events.
> -- 

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