multi-touch-dev team mailing list archive

[Chase Douglas <chase.douglas@xxxxxxxxxxxxx>]

On Tue, 2010-10-12 at 16:31 +0200, Henrik Rydberg wrote:
> On 10/12/2010 03:49 PM, Chase Douglas wrote:
> >> For this particular example, since the regions are listening to different
> >> gestures, there is actually knowledge available on the server side as well, so
> >> the combinatorial explosion does not seem to enter here.
> > 
> > This is the real issue: the server does not actually know about these
> > regions. In old school toolkits, each widget was a separate X window.
> > Modern toolkits don't do this anymore; instead, they have one X window
> > for the overall "window" and they draw all the widgets themselves. The
> > server doesn't have any information about where any widgets are in
> > windows anymore.
> 
> 
> Alright, I see you point. So given that we want to rebuild the role of the
> server on the client side, for good reason, it seems fair to ask why we want to
> have window-based touch propagation like in the proposed XI2.1.

There must be a way to propagate input among various "windows" still.
Different windows from different applications have differing toolkits
and event propagation. The common interface between them all is XInput
(or core X protocol). So the most straightforward path seems to be to
extend XI for MT support.

> > Going along with this, event propagation for widgets in a "window" is
> > performed in the toolkit. When using modern toolkits, X event
> > propagation is only used to propagate events between application
> > "windows" on screen.
> > 
> > (Here I use quotes around "window" to refer to what a normal user would
> > call an application window, in contrast to the X definition of a
> > window.)
> > 
> > This leads us to the gesture recognition mechanism Peter and I have been
> > discussing. Since we can't perform gesture recognition in the server, we
> > have to potentially perform recognition twice: first at the system-wide
> > level, then potentially at the application level if no system-wide
> > gestures were recognized. One method for doing this is XI 2.1 passive
> > grabbing.
> 
> 
> It seems to me another solution would be to route the events directly to the
> client side and use a more modern event propagation model.

This sounds like another client-server model, but with a different
server now. I'm not sure how this solves the event propagation issues
with client side toolkit rendering, and I only see it duplicating what
could be done more naturally in the window server input layer.

-- Chase