For USE=-gtk, /usr/share/applications/xinput_calibrator.desktop contains:
Exec=/bin/sh -c "xinput_calibrator; cat"
The reason for "cat" is that xinput_calibrator prints vital information on standard output upon termination. At least on LXPanel + Openbox setup, this results in "Cannot parse command line arguments" message. The problem is with the quotes; suggest replacing the line with (working with LXPanel):
Exec=sh -c xinput_calibrator;read\ x
Using "read" instead of "cat" here so that the user can just it Enter instead of closing the window (or non-intuitive Ctrl-D). An argument to "read" is required in dash.
Another option would be a wrapper script.
Created attachment 356538 [details]