> Hi Charlie,
>
> Pixel coordinates won't be enough, in general. Digitizers used for
> handwriting recognition often have much higher resolution than the
> LCDs, and the extra information is vital for good handwriting
> recognition, particularly for Asian languages.
I agree...
>
> I've integrated Asian handwriting recognition libraries into OSes
> which were not designed with this in mind, and I had to hack things
> up get digitizer-resolution coordinates.
>
> Plus, I think it'd be nice to decouple the digitizer API from a
> specific screen resolution.
>
Yup. Not just nice, but essential for some applications. This implies
the driver interface(s) should be in device coordinates to me, rather than
X coordinate systems.
There are two interfaces in X that have to be built: one in which the touch
screen is being used as the primary pointer, and then some other way to
deal with it in all its glory, almost certainly via the X Input extension.
(Un)fortunately, the X Input extension is something I haven't ever dealt
with, so I'll have to spend some time figuring things out. This was going
on about the same time as I was last working on X related topics (the XSync
extension).
Keith Packard knows quite a bit about the input extension (he and Bob
Scheifler ripped it apart and put it back together again some years ago),
and we're talking to each other about how in general we need X input to
get redone (note that while touchscreen is burning for handhelds, that
the widespread deployment of USB over the next year is going to require
this issue to get visited in a general sense for X; Keith is also interested
in handheld computing). Some work needs to be done to X in general in
this area, as the input extension does not have the concept of devices
coming and going (plug and play kinds of hardware weren't on the drawing
board in the early '90's). So not all the cultural history has been lost.
If we need to add an extension to make this all work, we can.
So we'll probably have to do a bit of work to X in general and while we're
at it, should ensure there be some way to get both screen coordinates from
the X server, and higher resolution coordinates for applications that need
them.
- Jim
--
Jim Gettys
Technology and Corporate Development
Compaq Computer Corporation
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