Workbench arguments are sent to an application when it is started. There
are also special facilities in Release 2 of Workbench that allow an
application that is already running to get additional arguments.  These
special facilities are known as AppWindow, AppIcon and AppMenuItem.

An appwindow is a special kind of window that allows the user to drag
icons into it.  Applications that set up an AppWindow will receive a
message from Workbench whenever the user moves an icon into the AppWindow.
The message contains the name of the file or directory that the icon
represents.

An appicon is similar to an appwindow.  it is a special type of icon that
allows the user to drag other icons on top of it.  Like AppWindows, an
application that sets up an AppIcon will receive a message from Workbench
whenever the user moves another icon on top of the AppIcon.  The message
contains the name of the file or directory that the moved icon represents.

An appmenuitem allows an application to add a custom menu item to the
usual set of menu choices supported by Workbench.  An application that
sets up an AppMenuItem will receive a message from Workbench whenever the
user picks that item from the Workbench menus.

When an application receives the messages described above, the message
will include struct wbarg *am_arglist containing the names (wa_name) and
directory locks (wa_lock) of all selected icons that were passed as
arguments by the user.  This am_ArgList has the same format as the
sm_arglist of a wbstartup message.

 workbench library functions    an appmenuitem example 
 an appicon example             an appwindow example