[Multi-touch-dev] [RFC XI 2.1] current issues

Daniel Stone daniel at fooishbar.org
Tue Dec 7 15:44:19 PST 2010


On Tue, Dec 07, 2010 at 10:54:37PM +0100, Denis Dzyubenko wrote:
> On 7 December 2010 22:44, Henrik Rydberg <rydberg at euromail.se> wrote:
> >> 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.
> >
> >
> > The min/max of the major/minor (aka width/height) is actually not that important
> > - they are all calibrated in devices coordinates, so using the same scale for
> > all of x/y/major/minor gives you the best result.
> well I still do not know what _is_ the scale. Actually I am not using
> MTAbsX/Y right now - I mainly rely on the root_x/root_y properties.

Right, so that would explain why you're getting screen-scaled
co-ordinates ... if you want unscaled, look at the x and y valuators
attached to the event, rather than root_{x,y}, which is by definition in
screen co-ordinate space.

> I am writing this email from a macbook - at it feels like mac moves
> the mouse cursor for the same distance on the screen as I physically
> moved my finger on the touchpad (that is if you ignore acceleration
> and move it slow) - that results in my next question - getting a
> physical size of the device.

That's not really multitouch per se, but just a matter of providing the
right general input properties.  Looking at the bcm5974 driver, which is
used for my MacBook Air, it doesn't have any way to read the physical

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