It returns the GdkContentProvider to use for the drag that is about
to start. The default handler for this signal returns the value of
the [property@Gtk.DragSource:content] property, so if you set up that
property ahead of time, you don't need to connect to this signal.
Emitted when a drag is about to be initiated.
It returns the GdkContentProvider to use for the drag that is about to start. The default handler for this signal returns the value of the [property@Gtk.DragSource:content] property, so if you set up that property ahead of time, you don't need to connect to this signal.