[Linuxwacom-devel] wacom tablet emulation

[Guennadi L. <g.l...@gm...>]

Hi all,

I have a Linux-powered embedded device with a keyboard, an LCD monitor and 
a touchscreen, and ethernet (think of it as of a PDA). And I'd like to use 
it as a (primitive) graphics tablet. A quick look around made me think 
there're not many tablets apart from wacom. So, I'd just write a server 
for my PC, a client for the PDA, which would mostly forward touchscreen 
events, plus mode-switching events, generated by pressing some keys on the 
keyboard. The server would just communicate over a pipe (if 1 direction is 
enough and no ioctl's are required) or a PTY (thanks to Glynn Clements for 
the idea) with the X-driver.

Now, that's where my question is - I guess, it is enough to implement 3 
modes (cursor, stylus and eraser) and send coordinates plus pressure, 
right? But what exactly is the protocol that the X-wacom driver expects? I 
first thought, I would write an own primitive generic X graphics-tablet 
driver. But, I guess, at least for the beginning, it would be better / 
easier to stick to an existing one, that means, to wacom.

I am also not sure about coordinates. I know touchscreens work with 
absolute and mice with relative coordinates. I would've thought, for a 
tablet relative coordinates would be easier / more natural. But I saw 
mentioning of both absolute and relative coordinates in the code. What 
should I deliver?

Thanks
Guennadi
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Guennadi Liakhovetski