$Id: README.md 11496 2026-01-17 00:15:43Z cfrees $

forest-ext

Small extensions for Sašo Živanović's fantastic Forest package.

Currently the package provides the following Forest libraries:

• ext.ling (simple wrapper styles)
• ext.multi (children with multiple parents)
• ext.tagging (produce tagged PDF)
• ext.utils (minor tweaks)

Debugging versions of all libraries are provided.

Licence

Copyright 2025-2026 Clea F. Rees

This work may be distributed and/or modified under the conditions of the LaTeX Project Public License, either version 1.3c of this license or (at your option) any later version. The latest version of this license is in https://www.latex-project.org/lppl.txt and version 1.3c or later is part of all distributions of LaTeX version 2008-05-04 or later.

This work has the LPPL maintenance status maintained'. The Current Maintainer of this work is Clea F. Rees.

This file may only be distributed together with a copy of the package chronos. You may however distribute the package chronos without such generated files.

This work consists of all files listed in manifest.txt.

Features

Forest is incompatible with the LaTeX Project's code for producing tagged PDF. ext.tagging enables Forest trees to be included in tagged documents by auto-generating alternative text based on the content of trees' nodes and edge labels. The result can be configured using Forest options and registers and/or providing custom plugs for the provided sockets.

I find myself using certain style tweaks repeatedly in both my own documents and answers on TeX SE. A few of these are provided here for convenience:

• align parent with the middle child, if the parent has an odd number of

• add labels for levels or tiers at the edge of the tree;
• include children with multiple parents;
• 'pretty nice empty nodes' (for linguists).

Limitations

The tagging code, in particular, is far from being a panacea. Known limitations include the following.

The bounding box calculation is based on the size of the tree. In the best case, this will be almost but not quite correct. In such cases, I assume the dimensions should be perfectly satisfactory. However, in the worst case, the dimensions will be very wrong. If the code is otherwise useful, I will look into the possibility of calculating the dimensions at a later point. (Right now, the problem is that they are calculated too early and so do not account for additions in tikz keys, for instance.)

Trees are tagged with alt text or nothing. No other options are available. In particular, none of text, actualtext and artifact (all supported by latex-lab for TikZ) are provided. It would be easy to support artifact and actualtext, but I doubt these are useful for trees.

Content is provided as simple text. Mathematics, logic and other symbolic markup is NOT rendered into luamml, xml or html. No associated files are written or embedded. It is, to say the least, unclear how content of this kind should be tagged. alt text is almost certainly a poor substitute, but there is not currently any obvious way to improve this.

It would be relatively straightforward to write a structured xml or similar to represent the tree. Unfortunately, I don't believe anything is available to make use of such a file. Individual formulae could be marked up as luamml, but in the absence of some standard way to represent the structure of the tree, this does not seem especially useful.

A hybrid consisting of alt text with luamml components might work for maths and, possibly, logic and linguistics, but that seems alien to the framework in the PDF specification. alt text is designed, as far as I can tell, for pictures. Trying to fit linguistic analyses or formal proofs into that space is unlikely to yield satisfactory results.

But these limitations are imposed by the various technical specifications and far beyond the control of any package.

(Possibly trees could be mapped to a specialised structure in the tagged content, which is, after all, itself arranged as a tree. But I am not certain whether a structure of that kind is possible within the tagging framework generated by the LaTeX format or if it is even permissible according to the somewhat complex specifications for accessible PDF. If that was possible, symbolic content might then be marked up as such, without disconnecting it from the structure.)

Code Repositories

Code for the package is hosted at https://codeberg.org/cfr/prooftrees For convenience, the repository will be mirrored at https://github.com/cfr42/prooftrees

Contact Details

Bug reports, feature requests etc. should be filed at https://codeberg.org/cfr/prooftrees/issues

Clea F. Rees Version 0.1 2026-01-17

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