Skip to content

alias LigaturingCallback

(alias) LigaturingCallback = fun(head: Node, tail: Node) -> false?

Apply ligaturing to a node list.

No return values. This callback has to apply ligaturing to the node list it receives.

You don't have to worry about return values because the head node that is passed on to the callback is guaranteed not to be a glyph_node (if need be, a temporary node will be prepended), and therefore it cannot be affected by the mutations that take place. After the callback, the internal value of the “tail of the list” will be recalculated.

The next of head is guaranteed to be non-nil.

The next of tail is guaranteed to be nil, and therefore the second callback argument can often be ignored. It is provided for orthogonality, and because it can sometimes be handy when special processing has to take place.

Setting this callback to false will prevent the internal ligature creation pass.

You must not ruin the node list. For instance, the head normally is a local par node, and the tail a glue. Messing too much can push LuaTeX into panic mode.

Reference:

😱 Types incomplete or incorrect? 🙏 Please contribute!