split
Modifies @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.
Return
new item representing text before @split_index, which should be freed with method@Pango.Item.free.
Parameters
splitIndex
byte index of position to split item, relative to the start of the item
splitOffset
number of chars between start of @orig and @split_index