"Multitouch" on FR ... imho should be possible to mimic

Helge Hafting helge.hafting at hist.no
Wed Mar 25 14:37:39 CET 2009

The Digital Pioneer wrote:
> It's tough to say until someone tries it. I don't have the GUI expertise 
> to do anything of the sort, but I'd love to see someone try it.

Testing is easy - no expertice needed.

Edit /etc/X11/Xserver
You'll find the parameter list for the xserver under a GTA02 (or GTA01) 
heading. Currently, it is:

ARGS="$ARGS -dpi ${DPI} -screen ${SCREEN_SIZE} -mousetslib -hide-cursor 
-root-ppm /usr/share/pixmaps/xsplash-vga.ppm vt1"

Remove the "-hide-cursor", then restart X or just boot the thing.

You will now get a visible mouse cursor, shaped like a X. It always move 
to wherever the touchscreen driver believe you're touching the screen.

Touch the screen, the X moves under your finger. Lift your finger, and 
you'll see it. Touch or drag with a stylus, and you'll see the mouse 
cursor move around. Just like on a PC screen.

Now touch down with two fingers, and see the mouse cursor move/jump to 
somewhere inbetween. That is what the touchscreen driver "sees", that is 
what software can _try_ to interpret as a gesture.

Try it, see for yourself. Do the midpoint seem stable enough to resize
a window? If not, is it at least stable enough to detect a rough 
gesture? Do it slide wildly as you move your fingers?

I just tested myself.
With firm pressure, the cursor stays between my fingers. There is some 
hight-frequency jitter as firmly pressed fingers slide - this can 
probably be filtered out.

With normal light pressure and one moving finger, the cursor slides back 
and forth between the midpoint and the stationary finger. Apparently, 
the moving finger almost disapper at times. The cursor is always closer 
to the stationary finger. No surprise - it is natural to apply more 
pressure with a stationary finger. Especially if the device is hand-held.

If I hold two fingers on the screen, I can move the cursor back and 
forth between the two positions with precision, by varying finger 
pressure. One could control a 2D sidescroll game this way, except it'd 
be way easier to just use the stylus for direct control.

Helge Hafting

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