Type Alias OnPush 

pub type OnPush = Box<dyn for<'a> Fn(UndoOrRedo, CounterSpan, Option<DiffEvent<'a>>) -> UndoItemMeta + Send + Sync>;

When a undo/redo item is pushed, the undo manager will call the on_push callback to get the meta data of the undo item. The returned cursors will be recorded for a new pushed undo item.

Aliased Type

pub struct OnPush(/* private fields */);