how image draw on Desktop by xorg

[pintu mehta]

Hi All
  which function of xorg source code responsable to draw a image on
Desktop or how is draw image on Desktop.i am new in this field but i
guess some structre should be there who pass all x,y cordinate
information to draw a any image on desktop....i m not able to get how
any event like mouse click or my computer icon click control by xorg.

Regards
pinto