To install xfce4-panel-dev just follow these instructions.
sudo apt-get install xfce4-panel-dev
Which will install xfce4-panel-dev and any other packages on which it depends.
|Maintainer||Debian Xfce Maintainers <firstname.lastname@example.org>|
|Description||Xfce4 panel development files Xfce4 panel, the main panel of Xfce4 desktop environment. The files in this package are mainly going to be of interest for you if you intend to code applications which use some of the Xfce4 C panel functions.|