How to change root window coordinates

["Matthew Jiang" <gobayarea gmail com>]

I was porting gkt to an embeded system. The problem is that I always got
unwanted display offset on LCD.
I used gdk_window_get_root_origin function get origin position and found
root_x equals a wiered number not zero.
How could I fix this problem and can I reset coordinate by hand?

Thank you,

Matthew.