This function registers a rich text deserialization @function along with its @mime_type with the passed @buffer.
the format’s mime-type
the deserialize function to register
@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.
2.10
See Implementation
This function registers a rich text deserialization @function along with its @mime_type with the passed @buffer.