how the wallpaper is displayed???

["Wang Qiang" <qiang wang cs2c com cn>]

i'm using gnome 2.6 desktop environment
my problem is how the wallpaper is displayed?

what i know right now:
1.I read the gnome-background-properties,it set the 
wallpapers that will be displayed on the desktop

2.gnome-background-properties sets the wallpaper info in 
$home/.gnome2/backgrounds.xml and 
$home/.gconf/desktop/gnome/background/%gconf.xml

3.as i imagine,i think the wallpaper is displayed under the 
fllowing steps:
    a. the gnome-background-properties set the wallpaper 
info in the 2 xml files
    b. gconfd notify "some program" to read the 2 newly 
written xml files to get the wallpaper info and display it.

question:
i'm not sure of the steps above,is it really that way?
and i want to know what the program is in step b

thanks ^_^