[RFC XI 2.1] current issues

Peter Hutterer peter.hutterer at who-t.net
Tue Dec 7 17:48:50 PST 2010

On Tue, Dec 07, 2010 at 10:36:36PM +0100, Denis Dzyubenko wrote:
> On 7 December 2010 20:07, Daniel Stone <daniel at fooishbar.org> wrote:
> >> Chase, Daniel: would be nice to put packages with debugging symbols to the ppa.
> >
> > I have nothing to do with the PPA, sorry: I run Debian, and only test
> > against master.  As for the crash, I don't have a Magic Trackpad either,
> > but will try to get my hands on one.
> I would like to be able to test latest versions of the XI2.1 changes
> from time to time, and the easiest way (at least for me :P) is the
> ubuntu ppa with binaries. The last time I tried to compile modular
> xorg using the wiki and provided shell scripts I failed miserably.

there's been a tremendous amount of work done on the build scripts to get
xorg from master up and running. that, and git master is actually quite
usable these days, I haven't seen any real showstoppers for ages. the
situation has really improved.

> >> - Who is going to "adjust" valuators values for different devices?
> >>
> >> For example the Touch Minor and Touch Major valuators give me totally
> >> different values for N-Trig touch screen and for the Apple Magic
> >> Trackpad.
> >> On the N-Trig I usually get values around 400 for my finger pressing
> >> gently while the range is from 0 to 9600; while with the magic
> >> trackpad it is around 100 in the range 0 to 255.
> >
> > Hm, I'm not sure how much we can do here without a table of
> > device-specific scalings.  Maybe we just need to get better data from
> > the kernel.
> I guess different kernel driver for different device _will_ give you
> different data. Hence my question was in context of recent discussion
> - getting events through slave devices vs. master devices - I would
> expect the data to be "unified" so that clients won't need to have
> device-specific workarounds. I wouldn't be surprised if some
> parameters would need to be configurable - the only example that comes
> to my mind right now is again width/height of the touch - right now I
> do not know what the value means and just assume that value 255 (the
> maximum for magic trackpad) means 50 pixels wide.
> >> Another example is the MTAbsX valuator coming from the N-Trig - the
> >> range announced to be from 0 to 9600, while the value is actually in
> >> screen coordinates.
> >
> > Hm, the x/y/root_x/root_y co-ordinates are in screen co-ords, but the
> > valuators themselves (appended to the event) should be in device
> > co-ordinate space.  I'll check this out.
> With N-Trig those valuators are in screen coords - at least touching
> in the bottom-right corner gives me the value that matches exactly the
> resolution of the screen.
> >> Other than that it seems to be working fine and I am looking forward
> >> to having grabs implemented :) Awesome job guys!
> >
> > Thanks. :) Please do keep testing it out and let us know about any more
> > problems.  Right now, the main problem I'm tracking is related to grabs
> > and short-lived touches: the touch may be finished before the grabbing
> > client has a chance to process the data and release the grab to pass on
> > ownership.
> my understanding of grabs is pretty vague. I guess you are talking
> about non-synchronous grabs? Sounds like synch-grabs should be used
> all over the place instead of you want to handle short-lived touches.
> How does it work for fast mouse clicks? I would expect the timing of a
> short-lived touch be exactly the same as the timing of a mouse button
> press and release.
> > My current hunch is to hold TouchEnd events until any grabbing client
> > has asserted ownership of the touch, or the last grabbing client has
> > released it to be played to selecting clients.  This adds a little more
> > scope for clients to get it wrong, but I don't see any other way to make
> > it work, and this is how grabs work today too.
> oh and one more question. I guess it will not be possible to get
> additional information about the touch device unless the driver
> exposes it? In my case I would like to know the physical size of the
> device in metric units - the size of the magic track pad - I want to
> be able to match metric distance between two fingers on the touch pad
> to the distance of the feedback on the screen.

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