orig to cover only the text after split.index, and
returns a new item that covers the text before split.index that
used to be in orig. You can think of split.index as the length of
the returned item. split.index may not be 0, and it may not be
greater than or equal to the length of orig (that is, there must
be at least one byte assigned to each item, you can't create a
zero-length item). split.offset is the length of the first item in
chars, and must be provided because the text used to generate the
item isn't available, so pangoItemSplit can't count the char
length of the split items itself.pangoItemSplit(orig, split.index, split.offset)split.indexsplit.offsetorig and split.indexPangoItem] new item representing text before split.index,