How can I get the gnome-panel's size?

[TualatriX <tualatrix gmail com>]

Hello everyone:

I want to get something about gnome-panel.

   1. How can I get the number of gnome-panel? In the normal case, there
   are two gnome-panel in the GNOME desktop environment. But how to use gtk+ to
   get the information?
   2. If I get the gnome-panel, how can I get the panel's size? In normal
   case, its size is 24px.
   3. Someone may use dock(kiba-dock,awn), are they the same type to
   gnome-panel?

Does anyone know how to realize？
 Thanks!