evtouch questions (xorg 6.8.2)

McDonald, Michael-p7438c Michael.McDonald at gdc4s.com
Wed Mar 24 19:08:01 PDT 2010

We're trying to integrate an eGalax touch screen into our system and
we're running into a few issues. We're using xorg-x11 6.8.2 from RHEL4
with touchkitusb.c and evtouch (0.8.0) from RHEL5 (xorg 7.1). This
bizarre combo seemed like the best option for getting the touch screen
to work with RHEL4 without using the binary blob from eGalax. (No, we
cannot update Xorg nor the kernel.)

1) The sequence of X events we get are not correct when you press and
release the touch screen. We get a ButtonPress at the current cursor
location (where ever that might be!), followed by a PointerMotion to the
pressed location, followed by a ButtonRlease at the correct location. We
have "fixed" this by reporting the X and Y values before the key event
in the touchkitusb.c driver. Has anyone else seen this behaviour and how
did you fix it?

2) The touch screen doesn't seem to be debounced. We almost always get
multiple press/release sequences whenever you touch the screen. There
doesn't appear to be any debounce code in either of the drivers. Do all
touch screens bounce? How should we attempt to debounce the touch

3) Is there anyway to get evtouch to reread the calibration file without
restarting X? ev_calibrate will generate a new calibration file for us
but I don't see anything in evtouch that will reload it.

4) Is there anyway to conditionally configure the evtouch driver in the
xorg.conf file? Some of our systems have touch screens and some do not.
If you have the evtouch driver configured into the xorg.conf file but
don't have a touch screen connected, X will not start. I've attached our
xorg.conf file.


Mike McDonald
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