Drag data has the following properties:
Drag action type (ie GDK_ACTION_COPY, GDK_ACTION_MOVE).
Client specified arbitrary drag-and-drop type (a name and number pair).
Sent and received data format type.
Drag actions are quite obvious, they specify if the widget can
drag with the specified action(s), e.g. GDK_ACTION_COPY and/or
GDK_ACTION_MOVE. A GDK_ACTION_COPY would be a typical drag-and-drop
without the source data being deleted while GDK_ACTION_MOVE would be
just like GDK_ACTION_COPY but the source data will be 'suggested' to be
deleted after the received signal handler is called. There are
additional drag actions including GDK_ACTION_LINK which you may want to
look into when you get to more advanced levels of drag-and-drop.
The client specified arbitrary drag-and-drop type is much more
flexible, because your application will be defining and checking for
that specifically. You will need to set up your destination widgets to
receive certain drag-and-drop types by specifying a name and/or number.
It would be more reliable to use a name since another application may
just happen to use the same number for an entirely different
meaning.
Sent and received data format types (selection
target) come into play only in your request and received
data handler functions. The term selection target
is somewhat misleading. It is a term adapted from GTK+ selection
(cut/copy and paste). What selection target
actually means is the data's format type (i.e. GdkAtom, integer, or
string) that being sent or received. Your request data handler function
needs to specify the type (selection target) of
data that it sends out and your received data handler needs to handle
the type (selection target) of data
received.
