Too bad, apparently no-one knows.
I was lucky, however. A colleague of mine bought the touchscreen laptop a few months ago and didn't mind me playing around with it a bit when he was in the lab. This is what I figured out so far:
The touchscreen works flawlessly in Ubuntu 11.10, at least until you connect an external monitor. At that point the touchscreen is aligned to the combined original screen and external monitor, which means you cannot use the touchscreen properly.
The good news is that it works just like the Wacom drawing tablets. This means that you can change the monitor area for which the touchscreen operates. By tweaking the
Area property of all your devices you can get the touchscreen to work how you want it, for example by executing:
for pad in "Serial Wacom Tablet stylus" "Serial Wacom Tablet eraser" "Serial Wacom Tablet touch"
xsetwacom --set "$pad" Area 0 0 10000 10000
0 0 10000 10000 values are arbitrary (haven't had the time to figure this out).
My hero for today is chh, he figured out and posted how to do this on http://ubuntuforums.org/showthread.php?t=1527548. On this link you can also find his scripts to calculate the correct values. The
xsetwacom version he used is different from the one I downloaded today, so his scripts didn't do the trick for me. Still, with this link, you should be able to figure it out for yourself.
Long story short, if you're planning to buy the HP laptop I mentioned earlier, you should be able to get the touchscreen to work properly with an external display attached.
And I should get back to work now.
Update! I finally got my laptop this week and did some more in-depth analysis about the dual screen scenario described in this question.
Using xsetwacom --list you can get a list of the Wacom-like devices (i.e., your touchscreen). Using the id returned by this command, you can save yourself a lot of typing. In case you want to reproduce what I'm going to explain, it might be useful to know my exact configuration:
tomas@EliteBook:~$ xsetwacom --list
Serial Wacom Tablet stylus id: 16 type: STYLUS
Serial Wacom Tablet eraser id: 18 type: ERASER
Serial Wacom Tablet touch id: 19 type: TOUCH
Using id 16 I can get the current area settings (18 and 19 should give the same results here):
tomas@EliteBook:~$ xsetwacom --get 16 Area
0 0 26312 16520
What this value means I'll leave to the experts. For me, it is important to know that this means 100%. Whether or not the external display is connected, this value remains the same.
Trial-and-error gave me a decent touchscreen calibration for
xsetwacom --set 16 0 0 50000 22000. When you look into it a bit more, you'll see why this makes sense:
Define the correct calibration as
0 0 x y and the initial (what I called the 100%) setting as
0 0 x0 y0.
Knowing my resolution is 1280x800 for the laptop and 1920x1080 for the external monitor and the external monitor is positioned to the right of my laptop, the top part aligned, you'll notice that in the horizontal direction the correct factor is the ratio of my total resolution (for me, 1280+1920) over my desired touchscreen resolution (1280). This gives a factor I'll define as a = 2.5. In the vertical direction this is 1080 over 800, or b = 1.35.
You might want to read the sentence above again. To help you a bit, see this screenshot of arandr.
To obtain the perfect value for my horizontal area, x, Simply multiply x0 by factor a. Do the same for your vertical area, y = b*y0, and then repeat for all your touchscreen devices (pen, eraser, touch) and you're all set:
xsetwacom --set 16 Area 0 0 65780 22302
xsetwacom --set 18 Area 0 0 65780 22302
xsetwacom --set 19 Area 0 0 65780 22302
edit: hmm, that's weird, the required area for finger/touch is smaller than the other devices by about a factor 10.
If I missed anything or if I'm not clear, send me a message and I'll try to help out.