Gets the Layout used to display the entry.
The layout is useful to e.g. convert text positions to pixel positions, in combination with get_layout_offsets. The returned layout is owned by the entry and must not be modified or freed by the caller.
Keep in mind that the layout text may contain a preedit string, so layout_index_to_text_index and text_index_to_layout_index are needed to convert byte indices in the layout to byte indices in the entry contents.
the Layout for this entry