multi-touch-dev team mailing list archive

[Peter Hutterer <peter.hutterer@xxxxxxxxx>]

On Tue, Dec 07, 2010 at 11:44:19PM +0000, Daniel Stone wrote:
> > 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
> dimensions.

evdev and synaptics read the resolution value from the kernel and set up the
matching XI values.

:: whot@barra:~> xinput --list "SynPS/2 Synaptics TouchPad" 
SynPS/2 Synaptics TouchPad                      id=13   [slave  pointer  (2)]
        Reporting 3 classes:
                Class originated from: 13
                Buttons supported: 12
                Button labels: Button Left Button Middle Button Right Button Wheel Up Button Wheel Down Button Horiz Wheel Left Button Horiz Wheel Right None None None None None
                Button state:
                Class originated from: 13
                Detail for Valuator 0:
                  Label: Rel X
                  Range: 1472.000000 - 5472.000000
                  Resolution: 93000 units/m
                  Mode: relative
                Class originated from: 13
                Detail for Valuator 1:
                  Label: Rel Y
                  Range: 1408.000000 - 4448.000000
                  Resolution: 125000 units/m
                  Mode: relative

so that makes it 4.3 cm, which is woefully incorrect in light of my 5.5 cm
touchpad, but I guess that's just a conversion going wrong somewhere.

for clients, if there is a resolution reported by the kernel driver, it is
available through XI.

Cheers,
  Peter