Sources and Destinations
Things are dragged from sources to be dropped on destinations. Each source and destination has information about the data formats that it can send or receive, provided by Gdk::ContentFormats. A drop destination will only accept a dragged item if they both share a compatible format. Appropriate signals will then be emitted, telling the signal handlers which format was used.
Gdk::ContentFormats objects contain information about available GTypes and mime types (media types).