touchscreens in multiscreen setups
jacmet at sunsite.dk
Thu Dec 17 23:43:26 PST 2009
>>>>> "Keith" == Keith Packard <keithp at keithp.com> writes:
Keith> I'd say tablets and touch screens should report raw device coordinates
Keith> and let the X server transform them as appropriate. It'd be really cool
Keith> if we could make all absolute devices report position in floating point
Keith> using a [0..1] range on each axis. I think. The X server would then
Keith> transform those as appropriate. I think all that would take is a new
Keith> PostMotionEvent function that took doubles instead of ints; fixed
Keith> drivers would use that, broken drivers would continue to report
Keith> coordinates as they do today.
Does this also include calibration? Some touchscreens apply calibration
parameters in firmware (like nextwindow), so the coordinates you receive
are already calibrated, whereas others provide raw coordinates and we
need to do calibration in software.
It would be nice to have generic calibration support in evdev, instead
of doing this different for each touchscreen. Related to this is
how/where to store calibration parameters. Notice that it sometimes is
needed to recalibrate at runtime (E.G. on resolution change if you don't
have your screen set for scale to fullscreen / don't keep aspect).
Bye, Peter Korsgaard
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