A variety of data items, called output units directions, are associated with output units. They may be used in the formatting functions, and/or associated with a button (see Simple Navigation Panel Customization).
Each output unit direction has a name and a reference to the unit they
point to, when such an unit exists. The unit is either a
global unit (for example, the Top output unit) or relative to the
current output unit (for example, the next output unit). Such relative
output units are determined with respect to the document structure defined
by the section structuring commands (@chapter,
@unnumbered…) or by the nodes if the node pointers are
specified on @node lines or in menus (see Two Paths in Texinfo).
Here is the list of global output units directions:
An empty button.
Top output unit.
First output unit in reading order.
Last output unit in reading order.
About (help) page.
Table of contents.
Overview: short table of contents.
Corresponds to the Footnotes output unit (see Output Units).
The first output unit with @printindex.
Here is the list of relative output units directions:
The current output unit.
Next output unit in reading order.
Previous output unit in reading order.
Next chapter output unit.
Beginning of this chapter, or previous chapter if the output unit corresponds to a chapter.
Next section output unit at the same level.
Previous section output unit at the same level.
Up section.
Next node output unit.
Next node output unit in node reading order.
Previous node output unit in node reading order.
Previous node output unit.
Up node output unit.
Relative direction are each associated with a variant, with
‘FirstInFile’ prepended, which points to the direction relative
to the first output unit in file. For example, FirstInFileNodeNext
is the next node output unit relative to the first output unit in file.
The ‘FirstInFile’ directions are usually used in footers.