C api for an application to access the menus of its icon in the dock

[Dan Hitt]

Some applications which run on ubuntu have more extensive menus their
dock icons than others.

For example, Firefox and Terminal both gives ways to create a new
window directly from their dock icons, while (e.g.) gimp does not.

So i assume that this means that there is an api that an application
can use to manage its dock menus.

Is this the case?

Is there a C version of this api?

Where is it documented?

And how could i look up this information in the system docs?

Thanks in advance for any info.

dan