RFC: multitouch support v2

Kristian Høgsberg krh at bitplanet.net
Thu Dec 22 07:15:05 PST 2011

On Thu, Dec 22, 2011 at 1:45 AM, Chase Douglas
<chase.douglas at canonical.com> wrote:
> On 12/21/2011 09:34 AM, Tiago Vignatti wrote:
>> From: Tiago Vignatti <tiago.vignatti at intel.com>
>> Hi,
>> Following Kristian suggestions, I updated the patchset with the following:
>> - driver now accumulates input coordinates to send along touch_down
>> - updated the protocol touch_down event with surface field, meaning the focus
>>   surface of a touch device
>> - compositor now uses a touch_focus pointer (self explicative), where it's
>>   picked when the first finger is down; all further events go there until it
>>   gets released
>> - not doing pointer emulation for now; that will come next.
> Do we really want pointer emulation in the window server? I can tell you
> from first-hand experience it's a nightmare. Toolkits should be updated
> to handle touch events properly, with an option to receive touch events
> and emulate pointer events for applications that aren't ready for touch
> event handling.

I don't think we do.  I'm not 100% sure yet, which is why I want to
focus on just the basic touch events for now.  I agree that since you
have to port a toolkit to Wayland anyway, you can just do pointer
emulation (if you must, real touch support is better, of course) in
the toolkit when you port it.

The one thing that makes me not quite sure is that client-side pointer
emulation won't be able to move the pointer sprite in response to
touch point 0 moving.  And maybe we don't need that.  On the other
hand, if the toolkit synthesizes enter/leave events in response to
touch events, it's going to be confusing when the actual pointer
enters a different surface.  It's also possible to make server-side
pointer emulation a per-client thing, similar to what Peter did for X.
 If a client subscribes to touch events, we don't do pointer

Anyway, for now the focus is on getting the basic touch events done
and get all the details worked out there.


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