Le 9 mars 10 à 23:27, Dmitry Torokhov a écrit :
With this regard, I am a big fan of the idea of having hierarchical
devices, just like with have hierarchical file systems. Each finger
on the dual-touch panel would be a device, child of the panel
device. Each would be equivalent to a mouse, and voila, the symmetry
is restored. Conceptually, saying (panel/finger1, any event) or
(panel, finger1 events) are equivalent; but in the first case the
routing is done by the OS and in the second case it has to be done
by the app, which breaks reusability. There are other interesting
perspectives, but I don't want to get carried away too much.
Theoretically it is nice but it practice the cases are differemt: with
mice you are dealing with 2 separate devices whereas with touchscreen
there is one and it is mater of interpretation whether 2 touches
should
be taken as independent events or a complex gestures.
Yes, but the whole point is that relying on the apps for the
interpretation is not always the right approach. In my "two users"
scenario, say one is using OpenOffice and the other is using a
browser. There's no reason why OpenOffice and the browser should
bother with multitouch. It is rather up to the OS (not necessarily
the kernel, probably rather X) to provide for the appropriate
configuration choice.
In other words: seen from inside the apps, the difference between
having one hardware device (the touchscreen) vs two hardware devices
(two mice) just does not make any sense :-)
Another example: NTrig's panel has two sensors, one that detects a
pen and on that detects fingers; they have chosen to multiplex the
two sensors through one USB interface; but is it one device or two
devices? As a programmer I don't know and I should not care.
Hierarchical devices would be a way for me to forget about this
irrelevant issue. Leave it to the OS and the user to choose which is
the right configuration.
St.
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