The `PangoItem` structure stores information about a segment of text.

You typically obtain `PangoItems` by itemizing a piece of text with func@itemize.

Create a new Item

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. @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 `pango_item_split()` can't count the char length of the split items itself.

Add attributes to a `PangoItem`.

The idea is that you have attributes that don't affect itemization, such as font features, so you filter them out using method@Pango.AttrList.filter, itemize your text, then reapply the attributes to the resulting items using this function.

The @iter should be positioned before the range of the item, and will be advanced past it. This function is meant to be called in a loop over the items resulting from itemization, while passing the iter to each call.