start
and end in the rich text format represented by format.gtkTextBufferSerialize(object, content.buffer, format, start, end)objectGtkTextBuffer format is registered withcontent.bufferGtkTextBuffer to serializeformatstartendformatlengthformats to be used must be registered using
gtkTextBufferRegisterSerializeFormat or
gtkTextBufferRegisterSerializeTagset beforehand.
Since 2.10