Ports that need Xfce libraries or
      applications set USES=xfce.
Specific Xfce library and
      application dependencies are set with values assigned to
      USE_XFCE.  They are defined in
      /usr/ports/Mk/Uses/xfce.mk.  The possible
      values are:
USE_XFCEIn this example, the ported application uses the GTK2-specific widgets x11/libxfce4menu and x11/xfce4-conf.
USES= xfce:gtk2 USE_XFCE= libmenu xfconf
Xfce components included this way will automatically include any dependencies they need. It is no longer necessary to specify the entire list. If the port only needs x11-wm/xfce4-panel, use:
USES= xfce USE_XFCE= panel
There is no need to list the components x11-wm/xfce4-panel needs itself like this:
USES= xfce USE_XFCE= libexo libmenu libutil panel
However, Xfce components and non-Xfce dependencies of the port must be included explicitly. Do not count on an Xfce component to provide a sub-dependency other than itself for the main port.
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