Drag-and-Drop in GTK+ and GNOME

Data Types

An important part of the information that must be negotiated during the drag is the type of the data. There must be a standard way of representing data types for the drag. The traditional way of representing data types for interprocess communication under X is by a standard set of names defined in the X Inter-Client Communication Conventions Manual (ICCCM). However, these names are out-of-date with respect to currently used data types, and since this registry is not widely used in the computing industry, there is little incentive to use it. For this reason, the Xdnd protocol specifies that data types are represented using standard MIME types. [1]

Although the choice of which MIME types to use depends on the applications needs, there are a few standard MIME types that are somewhat independent of application. For example, for simple strings, the MIME type txt/plain is used.

Notes
[1] MIME is defined in RFC's 2045-2049. A registry of MIME types is maintained by the Internet Assigned Numbers Authority (IANA).