fn update(
ch: &[TOCElem],
current: LogicalLevel,
max: SectionLevel,
old_slides: &RwSignal<u32>,
old_sections: &RwSignal<AllSections>,
old_paras: &VecMap<Name, (RwSignal<u16>, u16)>,
para_map: &VecMap<(ParagraphKind, Option<Name>), Option<Name>>,
)