= touchcal: touch screen calibration == SYNOPSIS *touchcal*  _Touchcal_ draws a cross-hair in each corner of the screen in turn(clockwise from the lower left hand corner), and waits each time for theuser to touch the centre of the cross-hair with the stylus. It thenprompts with a final cross-hair in the centre of the screen, and waitsonce more for the user to touch its centre with the stylus. The processis repeated until _touchcal_ can calculate a transformation matrix thatconsistently maps the touch panel to screen coordinates. It then writescorresponding calibration commands for _touch_(3) on its standardoutput, which can be saved in a file on the device, perhaps provided inNVRAM by _tinyfs_(3) or a file system in _ftl_(3). _Touchcal_ can be used both inside and outside the _wm_(1) environment,allowing calibration when the system is initialised, and whilst thewindow system is running. == FILES */dev/touchctl*::  reset or read existing settings == SOURCE */appl/cmd/touchcal.b* == SEE ALSO _touch_(3)