This function registers a rich text deserialization function along with its mime_type with the passed buffer. Since 2.10
the format's mime-type
function's user_data
a function to call when user_data is no longer needed
the GdkAtom that corresponds to the newly registered format's mime-type. [transfer none]
See Implementation
This function registers a rich text deserialization function along with its mime_type with the passed buffer. Since 2.10